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Operational performance evaluation of four types of exit ramps on florida's freeways

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Title:
Operational performance evaluation of four types of exit ramps on florida's freeways
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English
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Lu, Linjun
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University of South Florida
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Cross Road
Operational Analysis
Safety Analysis
Simulation
Tsis-corsim
Dissertations, Academic -- Civil Engineering Transportation -- Doctoral -- USF   ( lcsh )
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bibliography   ( marcgt )
non-fiction   ( marcgt )

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Summary:
ABSTRACT: This research focuses primarily on the analysis of exit ramp performance related to safety and operations. The safety analysis focuses on the impacts of different exit ramp types for freeway diverge areas and different factors contributing to the crashes that occur on the exit ramp sections. The operational analysis is based mainly on simulations by TSIS-CORSIM. Different ramp effects and guidance for selecting optimal exit ramp type are concluded. Issues related to ramp sections and crossroad sections are also demonstrated. Minimum ramp length and minimum distance between ramp terminal and downstream or upstream intersections are calculated. The operational analysis was conducted to determine different ramp effects and to provide guidance for selecting optimal exit ramp type. Comparisons of the operational performance of different types of exit ramps are made to present a method for choosing the optimal one. Some methods of evaluation (MOEs) are used to approach this objective, such as number of lane changes, average speed, delay time, etc. Data collection at 24 sites in Florida was conducted, and traffic simulations by TSIS-CORSIM were applied for analysis. Mathematical models were built to evaluate different impacts of these ramps based on simulations. All impact analysis is concluded to summarize a model for optimal exit ramp selection. In addition to ramp type evaluation and selection, issues related to ramp section and crossroad section are demonstrated. Minimum ramp length and minimum distance between ramp terminal and downstream or upstream intersections are calculated.
Thesis:
Disseration (Ph.D.)--University of South Florida, 2011.
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Includes bibliographical references.
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by Linjun Lu.
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Document formatted into pages; contains 101 pages.
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Includes vita.

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Operational Performance Evaluation of Four Types of Exit Ramps on Floridas Freeways by Linjun Lu A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Civil and Environmental Engineering College of Engineering University of South Florida Major Professor: John Lu., Ph.D. Yu Zhang, Ph.D. Abdul Pinjari, Ph.D. Rajaram Lakshminarayan, Ph.D. Michael Weng, Ph.D. Zhenyu Wang, Ph.D. Date of Approval: March 25, 2011 Keywords: Operational Analysis, Safety Analysis, Cross Road, TSIS-CORSIM, Simulation Copyright 2011, Linjun Lu

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Dedication I dedicate this dissertation to my family and friends, especially To my parents for opening my eyes to the world, To Dr. John Lu for his guidance and teaching, To Jane Zhang for her love and care, To Pan Liu, Tao Pan, Qing Wang, Bin Cao, Changjiang Zheng, Lei Zhang, and all other colleagues for their assist ance of this project, and To all saints in Tampa Local Church who helped me with my life.

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Acknowledgements This dissertation was deri ved from a research proj ect sponsored by Florida Department of Transportation (FDOT). The author would like to acknowledge support from FDOT for its assistance and suggestions leading to the successful completion of this dissertation. The contents of the report reflect the views of author, who is responsible for the facts, opinions, and accuracy of the information presented here. The contents do not necessarily reflect official views or policies of the sponsoring agency.

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Table of Contents List of Tables................................................................................................................i ii List of Figures................................................................................................................v Abstract....................................................................................................................... vii Chapter 1 Introduction...................................................................................................1 1.1 Background..................................................................................................1 1.2 Research Objectives.....................................................................................2 1.3 Sections of Exit Ramp.................................................................................5 Chapter 2 Literature Review..........................................................................................7 2.1 Previous Findings.........................................................................................7 2.2 Summary....................................................................................................13 Chapter 3 Methodology...............................................................................................15 3.1 Computer Simulation.................................................................................15 3.2 Simulation Procedure.................................................................................22 3.3 Methods for Operational Analysis.............................................................23 3.3.1 Freeway Section..........................................................................24 3.3.2 Ramp Section..............................................................................28 3.3.3 Crossroad Section.......................................................................30 Chapter 4 Data Collection............................................................................................33 4.1 Site Selection.............................................................................................33 4.2 Data Collection Equipment........................................................................35 4.3 Data Collection Procedures........................................................................38 4.4 Data Reduction...........................................................................................41 Chapter 5 Data Analysis and Results...........................................................................64 5.1 Freeway Section.........................................................................................65 5.1.1 Number of Lane Changes...........................................................65 5.1.2 Average Speed.............................................................................68 5.1.3 Delay Time..................................................................................71 5.1.4 Length Design for Deceleration Lane of Ramp Type I and IV................................................................................................72 5.1.5 Selection of Optimal Exit Ramp Type........................................76 5.2 Exit Ramp Section.....................................................................................78 i

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5.2.1 Ramp Length Design..................................................................78 5.2.2 Ramp Configuration....................................................................79 5.3 Crossroad Section......................................................................................81 Chapter 6 Conclusions.................................................................................................82 References....................................................................................................................84 About the Author..............................................................................................End Page ii

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List of Tables Table 1.1 Exit ramp type survey...........................................................................4 Table 4.1 Locations of 13 observed sites in Florida...........................................34 Table 4.2 Location of 24 exit ramps w ith classification of ramp type....................35 Table 4.3 Time period and method for all data collection......................................39 Table 4.4 I-4 at Conroy Road (NB)........................................................................42 Table 4.5 I-4 at Conroy Road (SB).........................................................................43 Table 4.6 I-4 at Altamonte Drive (SB)....................................................................44 Table 4.7 I-4 at Altamonte Drive (NB)...................................................................45 Table 4.8 I-275 at 4th Street (SB)...........................................................................46 Table 4.9 I-75 at SR 56 (SB)...................................................................................47 Table 4.10 I-75 at SR 56 (NB)..................................................................................48 Table 4.11 I-4 at CR 579 (WB).................................................................................49 Table 4.12 I-4 at CR 579 (EB)..................................................................................50 Table 4.13 I-275 at Ulmerton Road (SB)..................................................................51 Table 4.14 I-4 at SR 434 (SB)...................................................................................52 Table 4.15 I-4 at SR 434 (NB)..................................................................................53 Table 4.16 I-75 at Fowler Avenue (SB)....................................................................54 Table 4.17 I-75 at Fowler Avenue (NB)...................................................................55 Table 4.18 I-4 at I-75 (SB)........................................................................................56 Table 4.19 I-4 at I-75 (NB).......................................................................................57 iii

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Table 4.20 I-275 at Hillsborough Avenue (SB)........................................................58 Table 4.21 I-275 at Hillsborough Avenue (NB)........................................................59 Table 4.22 I-4 at Universal Blvd. (NB)....................................................................60 Table 4.23 I-4 at Universal Blvd. (SB).....................................................................61 Table 4.24 I-4 at Lee Road (SB)...............................................................................62 Table 4.25 I-4 at Lee Road (NB)..............................................................................63 Table 5.1 Change of selected variables...................................................................64 Table 5.2 Calibrated global parameter s ..................................................................65 Table 5.3 Calibration and validation results...........................................................65 Table 5.4 Coefficient values...................................................................................68 Table 5.5 Coefficient values...................................................................................71 Table 5.6 Coefficient values...................................................................................72 Table 5.7 Minimum deceleration lane....................................................................76 Table 5.8 Comparisons of exit ramp types.............................................................76 Table 5.9 Selection of optimal exit ramp................................................................78 Table 5.10 Minimum ramp length............................................................................79 Table 5.11 Observed ramp length.............................................................................80 Table 5.12 Relative speed S.D..................................................................................80 Table 5.13 Minimum distance between ramp terminal and downstream intersection..............................................................................................81 Table 5.14 Minimum distance between ramp terminal and upstream intersection .................................................................................................................81 iv

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List of Figures Figure 1.1 Type 1 single-lane exit ramp with a taper...............................................3 Figure 1.2 Type 2 single-lane exit ramp without a taper..........................................3 Figure 1.3 Type 3 two-lane exit ramp with an optional lane....................................3 Figure 1.4 Type 4 two-lane exit ramp without an optional lane...............................4 Figure 1.5 Main sections for analysis.......................................................................6 Figure 3.1 TSIS interface........................................................................................16 Figure 3.2 NETSIM and FRESIM in TSIS.............................................................21 Figure 3.3 Number of lane changes........................................................................24 Figure 3.4 Exit ramp configurations.......................................................................29 Figure 3.5 Distances between ramp terminal and downstream intersection...........31 Figure 3.6 Distances between upstrea m/downstream intersection and ramp terminal..................................................................................................32 Figure 4.1 Scattergrams of 13 observed sites in Florida.........................................34 Figure 4.2 Data collection equipment.....................................................................36 Figure 4.3 Location of devi ces for data collection.................................................40 Figure 5.1 Number of lane changes vs. ramp volume............................................66 Figure 5.2 Number of lane changes vs. freeway volume........................................67 Figure 5.3 Number of lane cha nges vs. number of through lanes..........................67 Figure 5.4 Average speed vs. volume.....................................................................69 Figure 5.5 Average speed vs. traffic exit rate.........................................................69 v

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Figure 5.6 Average speed vs. number of through lanes..........................................70 Figure 5.7 Speed S.D. vs. length (type I, 2 through lanes).....................................73 Figure 5.8 Speed S.D. vs. length (type I, 3 through lanes).....................................73 Figure 5.9 Speed S.D. vs. length (type I, 4 through lanes).....................................74 Figure 5.10 Speed S.D. vs. length (type IV, 2 through lanes)...................................74 Figure 5.11 Speed S.D. vs. length (type IV, 3 through lanes)...................................75 Figure 5.12 Speed S.D. vs. length (type IV, 4 through lanes)...................................75 vi

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Abstract This research focuses primarily on the analysis of exit ramp performance related to safety and operations. The safety analysis focuses on the impacts of different exit ramp types for freeway diverge areas and di fferent factors contributing to the crashes that occur on the exit ramp sections. Th e operational analysis is based mainly on simulations by TSIS-CORSIM. Different ra mp effects and guidance for selecting optimal exit ramp type are concluded. Issues related to ramp sections and crossroad sections are also demonstrated. Mini mum ramp length and minimum distance between ramp terminal and downstream or upstream intersections are calculated. The operational analysis was conducted to determin e different ramp effects and to provide guidance for selecting optimal exit ramp type. Comparisons of the operational performance of different types of exit ramps are made to present a method for choosing the optimal one. Some methods of evaluation (MOEs) are used to approach this objective, such as number of la ne changes, average speed, delay time, etc. Data collection at 24 site s in Florida was conducted, and traffic simulations by TSIS-CORSIM were applied fo r analysis. Mathematical models were built to evaluate different impacts of th ese ramps based on simulations. All impact analysis is concluded to summarize a m odel for optimal exit ramp selection. In addition to ramp type evaluation and selec tion, issues related to ramp section and vii

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crossroad section are demonstrated. Mi nimum ramp length and minimum distance between ramp terminal and downstream or upstream intersections are calculated. viii

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Chapter 1 Introduction 1.1 Background In Florida, several types of exit ramps are used for traffic to exit freeways (i.e., Interstate and Turnpike systems). Drivers exiting freeways need to make decisions and execute maneuvers (i.e., lane change or lane merge) prior to the exit ramp in order to access crossroads at interc hanges. If the exit ramps are not sufficiently long, drivers must complete their driving maneuvers within a short distance, resulting in potentially unsafe driving actions (i.e., fast-paced deceleration, lane changing, merging, unbalanced lane utilization, etc.), which will result in the development of shock-waves on upstream traffic, etc. Considering these factors, there are several issues and concerns that need to be a ddressed in selecting the optimum types of freeway exit ramp(s) to use at a given interchange. Some of these concerns include, but are not limited to, the operational performance and correlation between types of exit ramps, lane utilization, ge ometrics, land use along the crossroad, adequate distances for lane change, deceleration, and adequate distance for traffic to transit from the ex it gore to the downstream intersection, which includes weaving. These issues have not been studied in the past, and no clear guidelines, either federal (AASHTO Green B ook) or state, are cu rrently available in selecting exit ramp types. Therefore, there is a need to perform research under Florida 1

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conditions to specifically evaluate the ope rational performance for each exit ramp type to develop tailored guideli nes that address the issues. This need is especially significant considering the rapid increase in new developments close to freeway interchanges. The Florida Department of Transportation (FDOT), in joint cooperative efforts with local land us e agencies, can use the findings of this research to determine the type of exit ramps that should be constructed at a given location considering the prevailing conditions ap plicable to traffic, roadway, and land use developments. 1.2 Research Objectives The main goal of the research is to devel op tailored technical gui delines governing the selection of optimum exit ramp types to be used on Florida freeways. Typical exit ramp types include, but are not limited to, single-lane exit ramp with a taper, single-lane exit ramp without a taper, twolane exit ramp with an optional lane, and two-lane exit ramp without an optional lane (see Figures 1.1 to 1.4). 2

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Figure 1.1 Type 1 single-lane exit ramp with a taper Figure 1.2 Type 2 single-lane exit ramp without a taper Figure 1.3 Type 3 two-lane exit ramp with an optional lane 3

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Figure 1.4 Type 4 two-lane exit ramp without an optional lane Another objective is to present some design guidelines such as ramp length design, ramp curve design, super elevation design, mi nimal distance design on cross road, etc., which are also based on operational analysis. A survey was conducted to investigate the di stribution of different types of exit ramps in the state of Florida. Ta ble 1.1 shows that more than 95% exit ramps are of these four selected types. Thus, th e research on these four typical exit ramp types is very significant to Florida Highway system. Table 1.1 Exit ramp type survey Interstate Highway Length (mile) Type 1 Type 2 Type 3 Type 4 Other Total I-4 (Primary) 133 59 32 29 2 5 127 I-275 (Auxiliary) 64 35 14 6 1 2 58 I-295 (Auxiliary) 36 39 12 5 3 0 59 4

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All the analysis is based on a traffic operational performance evaluation. Video cameras were installed at selected site s to record vehicle movements so that performance data such as delay, operating speed, number of necessary or unnecessary lane changes/merges, lane utilization, vehicl e queue length, level of service, capacity, etc., could be obtained for each exit ramp t ype. After capture the existing data of exit ramps, the simulation software TSIS (Ver sion 6) was used to change possible variables to simulate different traffi c, geometric, and control conditions. 1.3 Sections of Exit Ramp The analysis of exit ramps includes three ma in sections: freeway s ection, ramp section, and crossroad section (see Figure 1.5). A fr eeway section refers to the upstream section of an exit ramp on a freeway, w hose length is 1500 ft, which is generally considered the impact distance of an exit ramp. Exit ramp section is from the start point of the ramp, the painted nose, to the e nd of the ramp, the ramp terminal. If there is a left or right taper at the ramp terminal the end of the ramp is the point where the taper intersects the crossr oad. A crossroad section is started from the downstream intersection of the ramp terminal to the upstream intersection of the terminal. All data for these two intersections were included in this area. 5

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Figure 1.5 Main sections for analysis 6

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Chapter 2 Literature Review Previous studies and findings of the operational performance on freeway diverge areas, exit ramps, and crossroad sections ar e reviewed and summarized in this chapter. The freeway is one of the primary compone nts of a transporta tion network and is categorized as the highest functional hi erarchy of the highwa y system. The grand reliance on this facility promotes the esse nce of applying a reliable, efficient, and sustainable infrastructure system; thus, th e operational performance is obviously an important consideration in freeway exit ramp design. Many factors are related to operations on freeways and thei r adjacent facilities. The wide variety of site geometric conditions, traffic volumes, ramp types, and design layouts could increase or decrease operation levels. 2.1 Previous Findings Al-Kaisy (1978) used a simulation appro ach for examining capacity and operational performance at freeway diverge areas. Freew ay diverge areas, and particularly those in the proximity of exit ramps, are often viewed as potential bottlenecks in freeway operations. The existing diverge procedures within the 1994 and 1997 Highway Capacity Manual updates are limited in that they do not provide a direct estimate of freeway capacity, nor do they model performance at oversaturated traffic conditions. Moreover, a parallel investigation of these procedures revealed some inconsistencies 7

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in predicting measures of performance at t hose critical areas. This paper describes the use of computer traffic simulation to expl ore the patterns of capacity and operational performance behavior at these areas under the impact of some key geometric and traffic variables. For this purpose, th e microscopic traffic simulation model INTEGRATION was selected to conduct an extensive experimental work on a typical ramp-freeway diverge section. Five control variables were investigated, namely, total upstream demand, off-ramp demand, length of deceleration lane, off-ramp free-flow speed, and number of lanes at mainline. Th e impact of upstream or downstream ramps was considered beyond the scope of this research. Except for off-ramp free-flow speed, the impact of other control variable s on capacity and operational performance was shown to be significant. Also, the simu lated trends of traffic behavior showed considerable agreement with logic and expectations in li ght of the current state of knowledge on freeway operations. Cassidy et al. (2000) conducted research on freeway traffi c near an exit ramp. He assumed that the freeway section near an exit ramp is a bottlen eck. A bottleneck with a diminished capacity is shown to have ar isen on a freeway segment whenever queues from the segments off-ramp spilled over and occupied its mandatory exit lane. Although the ramps queues were confined to the right-most exit lane, non-exiting drivers reduced their speeds upon seeing these queues, which diminished flows in all lanes. It was also shown that the lengt hs of these exit queues were negatively correlated with the discharge flows in th e freeway segments adjacent lanes, i.e., 8

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longer exit queues from the over-saturated off-ramps were accompanied by lower discharge rates for the non-exiting vehicles Whenever the off-ramp queues were prevented from spilling over in to the exit lane (by chan ging the logic of a nearby traffic signal), much higher flows were sustained on the freeway segment, and a bottleneck did not arise there. These obser vations underscore th e value of control strategies that enable diverging ve hicles to exit a freeway unimpeded. Newell (1998) studied the delays caused by a queue at a freeway exit ramp. This occurs when a queue from an exit ramp backs onto the freeway, causing a partial blockage of the right lane. Exiting vehicles are confined to the right lane but thru vehicles can travel in any lane. The two vehicle types in teract, but their queues must be treated separately. This illustrates a special case of a mode l of freeways with special lanes' formulated by Daganzo (1997). Whereas Daganzo presented a numerical scheme of calculating flows, th e emphasis here is on graphical evaluation of the complete evolution of the queue s. The graphical so lution more clearly illustrates the practical issues. Anon (1976) focused on the design and control of freeway off-ramp terminals, evaluating a more successful design and operating pr actices used at freeway exit-ramp terminals and concluded that the design of exit ramps should be related to both the freeway and the crossroad. Grades should be as flat as possible and, where possible, the entire ramp should be visible from the freeway exit. The ramp should have a 9

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relatively flat platform at the intersecti on with the crossroad. Adequate stopping sight distance must be provided throughout th e length of the ramp, and enough sight distance is needed at the in tersection to allow for safe turns. These suggestions can improve safety performance significantly. Xiao (2007) studied the minimum-length-requiremen t model for expressway off-ramp joint. To augment the capacity of off-ramp joint, a method to calculate its length is needed. With the definition and basic hypothesi s of off-ramp joint, the characteristic of its structure and traffic flow are analyzed. From a systematic viewpoint, kinematics, gap-acceptance theory, and probability theory were employed to establish the minimum-length-requirement model for expres sway off-ramp joint. While modeling, the more difficult traffic maneuver of r unning off the off-ramp road, finishing its interweaving, and running onto the left-turn lane of downstream intersection were taken into consideration comprehensively. For a newly constructed road, the required minimum length can be computed using the model. For an existing road, based on the comparison of the measured value and calcu lated value, the model is helpful for determining the reasons for congestion on the off-ramp jo int and taking corresponding improvement measures. Finally, the model was verified to be feasible through comparison with the simulation results of CORSIM (corridor simulation model). Li (2007) did research about factor s influencing free flow speed on expressway. In order to research the pattern of the fr ee flow speed (FFS) on the expressway, the 10

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measured FFS, the theoretical FFS and the 85 percentile speed a nd their correlation were analyzed statistically using the traffic data acquired by the loop vehicle detectors buried in the expressway in Shanghai. The attention was focused on the measure FFS, and the regression models between it and th e radius of the horizontal curve, between it and the distance to the inlet or from the exit ramp, and between it and the traffic saturation degree. On this basis, a model was presented to estimate the FFS on the expressway without the need of the field data, providing a base for evaluating the service level of the expressway operation system and estimating its traffic flow capacity. Bunker (2003) predicted minor stream delays at a limited priority freeway merge. He discussed the development and application of a limited priority gap acceptance model to freeway merging. In the limited priority model, drivers in the major stream at a merge area may incur delay in restoring sm all headways to a larger, sustainable minimum headway between them and the vehi cle in front. This allows minor stream drivers to accept smaller gaps. The head way distributions are assumed to be distributed according to Cowan's M3 model, whose terms were calibrated for this system. Minor stream minimum follow-on tim e was calibrated, and a realistic range of the critical gap identified. An equati on was developed for minimum average minor stream delay. 11

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A function was identified to model the re lationship between minor stream average delay and degree of saturation. The shape pa rameter of this f unction was calibrated using simulated traffic flow data, under thr ee different minor stream arrival pattern regimes. The model provides a useful m eans of comparing performance, through average minor stream delay, for varying mi nor and major stream flow rates and minor stream critical gap, under arri val patterns that differ due to traffic control upstream of the on-ramp. Minor stream delay is a particul arly useful measure of effectiveness for uncongested freeway merging as it relates dir ectly to the distance required to merge. Observations from the model developed provi de physical evidence that minor stream drivers incur lesser delay, or have a be tter chance of merging quickly, when they arrive at constant intervals as is the case under constant departur e ramp metering, than when they arrive in bunches downstream of a signalized inters ection, or even a semi-bunched state downstream of an unsignalized intersection. Zhou (2008) developed a methodology to evaluate th e effects of access control near freeway interchange areas. Access connections and signalized intersections within the functional area of an interchange can advers ely impact safety and operations at the interchange crossroad and on the freeway, and can cause the interchange to fail prematurely. Standard practice is to ac quire a minimum of 90 m (300 ft) of limited access right-of-way beyond the end of the acce leration/ deceleration lanes for rural interchanges and 30 m (100 ft) in urban areas. 12

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His study methodology included the following basic steps: (1) traffic operations analysis of the study interc hange with varying configur ations of signalized access spacing using CORSIM; (2) safety analysis of a sample of Florida interchanges with varied access spacing; and (3) cost/benefit analysis of acquiring varying amounts of limited access right-of-way. This study indicates that the long-term safety, operation, and fiscal benefits of purch asing additional limited access ri ght-of-way at interchange areas greatly exceeds the initial costs. The findings suggest that state transportation agencies and the traveling public may benef it greatly by an increase in the amount of limited access right-of-way at interchange ar eas to a minimum of 180 m (600 ft) and a desirable 400 m (1320 ft). A lthough the safety and operational benefits of managing access in freeway interchange influence areas are clear, the cost effectiveness of purchasing access rights at the time of interchange construction has not been established through nationalor state-leve l research. The primary objective of this study was to assess the relative costs and benefits of purchasing additional limited access right-of-way at the time of constructi on in lieu of retrofitting interchange areas after functional failure. 2.2 Summary Exit ramp is always an important research focus, such as ramp capacity, waving area operations, ramp configurati on, crash analysis on freeway and ramps, and etc. And previous research findings had already shown some results of such analysis. However, specific analysis on operational performance of different types of exit ramps hasnt 13

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conducted yet. Therefore, possible results a nd conclusions of this research are very helpful for exit ramp evaluation and selec tion, as well as some geometry design issues. 14

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Chapter 3 Methodology This chapter mainly describes the me thodology of this project, including a microscopic traffic simulation technique, st atistical modeling, and some design issues. The main contents consist of introducti on to simulation, simulation procedures, freeway section evaluation, ramp parameter design, cross road access spacing, etc. 3.1 Computer Simulation All operational analysis was based on tr affic simulation software TSIS-CORSIM. TSIS can satisfy all the requirements of this project. After data validation and calibration, variables were changed in TSIS to simulate different traffic situations, which saved much energy and time. All co llected data were input to TSIS for simulation, and output data provided analys is results for further calculation and comparison. The Federal Highway Administrations (FHWA) Traffic Software Integrated System (TSIS) is an integrated development envir onment that enables users to conduct traffic operations analysis. Built using component architecture, TSIS is a toolbox that contains tools that allow the user to define and manage traffic analysis projects, define traffic networks and create inputs for traf fic simulation analysis, execute traffic simulation models, and inte rpret the results of those models (Figure 3.1). 15

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TSIS is microscopic traffic software with a long history, which guarantees reliability and practicability. The history is as follows: Mid 1970s: UTCS-1 (Urban Traffic Control System) Mid 1980s: NETSIM Late 1980s: TRAF-NETSIM 1990: TSIS/NETSIM 1994: TSIS/FRESIM 1995: TSIS/CORSIM (DOS version) 1997: TSIS/CORSIM (Windows version) Figure 3.1 TSIS interface TSIS is a complete software package, and different individual tools are included. Each tool has its exclusive functi on. Here are 10 main compone nts in TSIS Version 6 and their use, which can help better understa nd how TSIS works, as described below: TShell: TShell is the graphical user interface for the TSIS integrated development environment. It provides a project view that enables you to 16

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manage your TSIS projects. It is also th e container for the pre-configured tools and any tools that you add to the su ite. See the TShell User's Guide for additional details. TSIS Next: TSIS Next contains the same type of functionality that can be seen in the TShell, TRAFED, and TextEditor component programs. TSIS Next is a quicker-and-easier version of TSIS th at contains specific advantages and disadvantages. Certain advanced CORS IM applications will continue to require TShell and TRAFED. By having access to both TSIS and TSIS Next on the same computer, you can choose whichever functionality you prefer. CORSIM: The CORSIM simulation consis ts of an integrated set of two microscopic simulation models (NETSIM and FRESIM) that represent the entire traffic environment as a function of time. NETSIM represents surface-street traffic and FRESIM repr esents freeway traffic. Microscopic simulations model the movements of i ndividual vehicles, which include the influences of driver behavior. Thus, the effects of very deta iled strategies, such as relocating bus stations or changing pa rking restrictions, can be studied with such models. CORSIM provides its own in terface in TSIS 6 that enables you to control the simulation and the accu mulation of traffic measures of effectiveness. See the CORSIM User's Guide for additional details. TRAFED: TRAFED is a graphical user interface-based edito r that allows you to easily create and edit traffic networ ks and simulation input for the CORSIM model. See the TRAFED User's Guide for additional details. 17

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TRAFVU: TRAFVU (TRAF Visualizat ion Utility) is a graphics post-processor for FHWAs CORSIM microscopic traffic simulation system. TRAFVU displays traffic networks, animates simulated traffic flow operations, animates and displays simulation output measures of effectiveness, and displays user-specified input parameters for simulated network objects. See the TRAFVU User's Guide for additional details. TSIS Text Editor: This editor is a sta ndard text editor that has the additional capability of "understanding" the CORSIM TRF file format. When editing a TRF file with this editor, the TShell output window displays text describing the entry field and record type at the current cursor position. Clicking a specific field description in the output window highlights the corresponding entry field in the displayed TRF file. Th is makes manual editing of the text file much easier than with previous text editors. See the TSIS Text Editor User's Guide for additional details. TSIS Script Tool: The TSIS Script Tool is a combined script editor and tool for executing Visual Basic Scripts. Using th e built-in TSIS interfaces, the Script Tool is a powerful mechanism for exte nding the functionality of the other TSIS components. We have also included two scripts with this release. One is a multi-run script that repeatedly r uns CORSIM on a test case, applying different random number seeds to each r un. The other script runs CORSIM on many different test cases. See the Script Tool User's Guide for additional details. 18

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TSIS Translator: The TSIS Translator converts TRF files for use by TRAFED. This translator also performs the reve rse operation of translating the TRAFED native format (TNO) files into TRF files for use by CORSIM and other tools. See the Translator User's Guide for additional details. TSIS Output Processor: The TSIS Output Processor enables the user to automatically compute selected statistics and summary data during multiple runs of CORSIM. The collected data is written to an Excel workbook, a comma-separated file, an XMLtagged file or a tab-separated text file. The Output Processor can also compute 95th percentile confidence intervals, and can recommend sample sizes (i.e., the nu mber of simulation runs that should be performed with varying random nu mber seeds) for achieving desired accuracy. The Output Processor has been redesigned for TSIS 6 to efficiently summarize any model result generate d by CORSIM. Cumulative MOEs may be obtained from the start of simulation, or just for the current time interval, or just for the current time period, or any combination of those three. CORSIM Runtime Extension (RTE): Although it comes pre-configured with a set of tools, TSIS provides a mechanis m by which an external application can interface directly with CO RSIM simulation. This type of application has become known as a CORSIM run-time extension (RTE). Run-time extensions can be built to replace existing logic in CORSIM, or to supplement the logic. The original run-time extensions were tailored for signal timing studies. However, the concept has been expa nded to support freeway monitoring, 19

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incident detection, ramp metering runtime extension packages, work zone control, and signalization. TSIS-CORSIM has a very strong capability with many applications, some of which are related to this project: Freeway and surface street interchanges, Signal timing and signal coordination, Freeway weaving sectio ns, lane adds and lane drops, Ramp metering and HOV lanes, Queuing studies i nvolving turn pockets and queue blockage, etc. TSIS-CORSIM combines two of the most widely used traffic simulation models, NETSIM for surface streets and FRESIM for freeways. FRESIM is mainly for freeway system, and NETSIM is for roadways other than freeways. Thus, in this project, NETSIM can be used to build up crossroads and parts of exit ramps, and FRESIM can be used to build up freeways and parts of exit ramps. Also, CORSIM can combine them into one ne twork. Figure 3.2 shows a network example combining NETSIM and FRESIM in TSIS. 20

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Figure 3.2 NETSIM and FRESIM in TSIS In addition, TSIS-CORSIM also provides seve ral demo projects for different subjects, which helps to understand the simulation pro cess. These demo projects are as follows: Actuated Control Demo: This project demonstrates the operation of actuated control in the CORSIM model. CORSIM City Demo: This project demons trates the capabilities of the TSIS package in creating and simulating a wide variety of different roadway configurations and interchanges. Incident Demo: This project demonstrates the effects of a freeway incident (accident) on a freeway and its surro unding arterials as modeled by CORSIM. 21

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EV Example: Emergency vehicles can cause signal pre-emption, follow specific routes, and travel at excess speeds. Interchange Demo: This project demons trates the operation of the CORSIM surface-street interchange feature. Surface and Freeway Demo: This combined surface-street and freeway project demonstrates many features of the CORSIM model, including intersection controller and bus operations. Left Hand Examples: This project dem onstrates left-hand drive within the CORSIM model, including intersection controller and roundabout operations. 3.2 Simulation Procedure There are several typical steps for a complete TSIS simulation application: Step 1: Geometry data input. This step includes nodes, links, frameworks, property of node and link. Deta iled factors are lane as signment, length, width, grade, curve, media n, sign, mark, etc. Step 2: Traffic data input. This step mainly inputs traffic volume and related data, such as hourly volume, heavy vehi cle, bicycle, pedestrian, bus, bus station, etc.; not only total volume needs to be input, but also volume for each turning direction should be indicated. Step 3: Traffic control da ta input. This step tells TSIS the type of traffic control. Normally, signalized control is used for intersections at ramp terminals, downstream intersections, or upstream intersections. Even some 22

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intersections are actuating control; they are considered as pre-time control intersections. Timing and pha sing data are observed during peak hours, which keeps them constant. Step 4: Simulation running. After all data are accomplished, TSIS will start running. During this step, all warnings and errors can be stated, which indicate necessary correction. Because traffic flow is random, all simulation files and models were running multiple times, and average outputs were considered the final results in orde r to eliminate randomness of traffic. Step 5: Data output: TSIS can pr oduce a report of all Measures of Effectiveness (MOEs), tables, and charts. Useful data are selected for further analysis. Step 6: Calibration: Some MOEs will be selected for calibration, such as queuing length at the intersection appro ach. TSIS output data and field data are compared to make sure the errors are under control. This step assures accuracy of the simulation. Step 7: Modeling: After data calibration is passed, useful data are chosen for mathematical modeling, presenting relationships among variables. 3.3 Methods for Operational Analysis The whole network of each observed site in TSIS was divided into three sections: freeway section, exit ramp section, and crossroad section. These sections were separated for further analysis. Different MOEs were presented to evaluate the 23

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performance for each section. And for w hole system calibration and validation, different sections were combined. 3.3.1 Freeway Section In the freeway section, the main task was to find out whether the impacts of different exit ramps are significantly different based on operational analysis. If the impacts are different, there is a need to select an optimal one under certain conditions. Based on previous studies and data collection, number of lane changes, average speed, and delay time are considered the meas ures of effectiveness for operational performance evaluation. (1) Number of Lane Changes The number of lane changes is the total number of vehi cles changing lanes in the freeway upstream section (1,500 ft before ex it ramp) within one hour (see Figure 3.3). Figure 3.3 Number of lane changes 24

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Number of lane changes is a significant f actor that impacts operational performance on freeway sections adjacent to exit ramps. This change is mainly caused by exiting traffic to the ramp. The larger the number of lane changes, the worse the operational performance of the freeway. One kind of cha nge is the exiting vehicles changing lanes from the left side thru lane to the right side ramp, which is called a mandatory lane change. The other kind of lane change happens between thru lanes just to find a better driving environment, which is an optional lane change. The last kind of number of lane change is the thru traffic changing la nes from the right side lane to the left. Several independent variables may affect th e number of lane changes, including ramp type, traffic volume, and number of thru lane s, etc. A mathematical model is presented to demonstrate the variable of number of lane changes. Eq. (1) ,...),,,,,(4321413 2 1XXXXXXfY Where, Y number of lane change X 12 ramp type II X 13 ramp type III X 14 ramp type IV X 2 freeway volume (vph) X 3 exit rate (%) X 4 number of thru lanes on freeway 25

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(2) Average Speed In addition to the number of lane change s, average speed on a freeway section is factor that can be used to estimate the impacts of the exit ramp. The larger of the average speed, the better the performance, and the less the probability of a crash. The variables of ramp type, traffic volume, and number of thru lanes contribute to speed. A prediction model to estimate average speed is as follows: Eq. (2) ,...),, ,2 3 2XXX fY ,, (43 1411X XX Where, Y average speed X 12 ramp type II X 13 ramp type II X 14 ramp type IV X 2 freeway volume (vph) X 3 exit rate (%) X 4 number of thru lanes on freeway By using TSIS simulation, many scenarios are sp ecified, such as the different levels of traffic, different thru lanes, and different ramp types. All the extended examples can help find the correlation ships. 26

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(3) Delay Time Delay time per vehicle on a freeway section indicates the impacts of the existence of the exit ramp. Ramp type is an important fact or contributing to it. Field data show that exit ramp types can affect control delay on a freeway near a ramp area. A prediction model is presented to estimate control delay per vehicle, and the format is the same as model for number of lane changes and average speed. Eq. (3) ,...),, ,2 3 2XXX fY ,, (43 1411X XX Where, Y delay time (s) X 12 ramp type II X 13 ramp type III X 14 ramp type IV X 2 freeway volume (vph) X 3 exit rate (%) X 4 number of thru lanes on freeway When different impacts of different ramp types are found under the same traffic and geometric conditions, there is evidence for choosing an optimal exit ramp for a certain situation. In addition to all three MOEs men tioned above, safety is another aspect for the selection. Results from the safety analysis also were used. 27

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(4) Length Design for Deceleration Lane of Ramp Type I and IV Besides number of lane change and speed standard deviation (S.D.), length design for the deceleration lane is anothe r important issue. For ramp t ypes I and IV, the length of the deceleration lane can be verified, a nd the change of length might impact the performance. In simulation, the length is changed from 100 ft to 1500 ft in TSIS to see the distribution of MOE speed S.D. under a different level of volume. Actually, AASHTOs Green Book has already presented the proper length for freeway exit lanes, but the standards are mainly base d on stop distance. New suggested distances are based on operational analysis. 3.3.2 Ramp Section There are two issues related to the ramp s ection: determining the minimal length for a ramp and discussing the ramp configuration. (1) Ramp Length Design Ramp length design is based on the assumption that the minimum length of ramp must meet the requirements of holding ex iting traffic, including queuing length, deceleration length, and perception-reaction di stance. The exiting traffic spilling back onto the freeway must be avoided. The decel eration distance can be calculated by the initial speed and the deceleration rate, a nd the perception-reaction distance depends 28

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on speed and time. Queuing length needs simulation, which depends on geometry and traffic conditions together. Several factors will affect the minimum ramp length, such as volume level, control type, number of lanes on ramp, ramp terminal etc. Thus, all the independent variables will be changed to simulate respectively, in order to find the minimal queuing length under each scenario. (2) Ramp configuration The AASHTO Green Book listed three kinds of exit ramp configuration: type A, type B and type C, as shown in Figure 3.4. A B C D1D2 A B C D1D2 Figure 3.4 Exit ramp configurations In a type A, the ramp terminal is close to the freeway, and the exit ramp is almost parallel to the freeway. This type is usua lly caused by limited land use. In type B, the ramp terminal is little farthe r away from the freeway and the length of the exit ramp is 29

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longer; the ramp is closer to straight, or th e curve is sharp. In a type C, ramp the terminal is far enough from the freeway, and the ramp curve can be made smooth. Two factors are changed that result in changes in operational performance, D 1 and D 2 (see Figure 3.4). Distance change is to find out how speed S.D. changes. A larger speed S.D. value under certain ramp conf iguration can cause potential problems. 3.3.3 Crossroad Section The main task related to crossroads is to determine the minimal distance between the ramp terminal and the upstream/downstream intersection. Take the distance between the ramp terminal and he downstream intersection as an example. Based on this assumption, it is calcul ated that the queuing length of vehicles on the crossroad does not block the traf fic coming out from the exit ramp. For distance between the downstream intersection and the ramp terminal, the weaving distance is also considered in addition to queuing length. Figure 3.5 shows the general method for calculating minimum distance. Ther e is not a specified minimal distance requirement between the ramp terminal and the upstream intersection, which is also the distance between two exit ramps at a diamond inte rchange. Several factors will impact this distance, such as geom etric configuration and land use. 30

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Figure 3.5 Distances between ramp term inal and downstream intersection A minimal distance is presen ted here mainly based on queuing length simulation. This method assures that queuing length will not sp ill back from segments between the two exit ramps, which will worsen thru traffic conditions on the crossroad. Figure 3.6 shows the simulation network in TS IS to test different distances when traffic volumes, signal timing plans, and the geometry conditions are changed. The minimum distance can be found under heavy traffic conditions. 31

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Figure 3.6 Distances between upstream/downstream intersection and ramp terminal 32

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Chapter 4 Data Collection This chapter mainly describes information about field data colle ction, including site selection, data collection equipment, data collection procedures, and data reduction. All collected field data were subject to simulation modeling and input requirements. The quality of data collection will impact the accuracy of the simulation results. Therefore, this part of the project was well prepared. 4.1 Site Selection Site selection must be determined first. There were 13 sites selected for data collection in Florida. The selection cr iteria for all these sites were based on discussions among FDOT project officials a nd USF researchers, with the following requirements: All sites are freeway interc hanges in central Florida. All sites are representative a nd typical in central Florida. All sites include the four different types of exit ramps. All sites serve a high traffic volume at peak hours. Table 4.1 shows the locations and area of the 13 sites. All are located in the Tampa Bay and Orlando areas in central Florida. Figure 4.1 shows the exact scattergrams of 33

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the observed sites on a map of Florida. Generally, each completed interchange contains two exit ramps on the two opposite sides, and only two interchanges have one exit ramp. Thus, there are 24 exit ramps for the 13 sites. Table 4.2 shows the 24 exit ramps with detailed classi fications of ramp types. Table 4.1 Locations of 13 observed sites in Florida No. Location Area 1 I-75 at SR 56 Tampa 2 I-4 at CR 579 Tampa 3 I-275 at Hillsborough Ave Tampa 4 I-75 at I-4 Tampa 5 I-275 at Ulmerton Rd St Petersburg 6 I-275 at 4th St St Petersburg 7 I-75 at Fowler Ave Tampa 8 I-4 at Universal Blvd Orlando 9 I-4 at Conroy Rd Orlando 10 I-4 at Lee Rd Orlando 11 I-4 at Altamonte Dr Orlando 12 I-4 at SR 434 Orlando 13 I-75 at CR 581 (Bruce B. Downs Blvd) Tampa Figure 4.1 Scattergram of 13 observed sites in Florida 34

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Table 4.2 Locations of 24 exit ramps wi th classification of ramp type Ramp No. Ramp Type Ramp Location Ramp Direction Number of Thru Lanes on Freeway Number of Lanes on Ramp 1 I-75 at SR 56 SB 2 1 2 I-4 at CR 579 WB 3 1 3 I-275 at Hillsborough Ave NB 3 1 4 I-275 at Hillsborough Ave SB 3 1 5 I-75 at I-4 SB 3 1 6 I-275 at 4 th St SB 4 1 7 I-4 at Universal Blvd SB 3 1 8 I-75 at CR 581 (BBD) SB 2 1 9 I-75 at Fowler Ave SB 3 1 10 I-4 at Lee Rd NB 4 1 11 I-4 at Lee Rd SB 4 1 12 I-4 at SR 434 SB 4 1 13 I-75 at SR 56 NB 4 2 14 I-4 at CR 579 EB 4 2 15 I-4 at Universal Blvd NB 4 2 16 I-4 at Conroy Rd NB 5 2 17 I-4 at Conroy Rd SB 5 2 18 I-4 at Altamonte Dr NB 4 2 19 I-4 at SR 434 NB 4 2 20 I-4 at Altamonte Dr SB 4 2 21 I-75 at CR 581 (BBD) NB 3 2 22 I-75 at I-4 NB 4 2 23 I-275 at Ulmerton Rd SB 4 2 24 I-75 at Fowler Ave NB 3 2 4.2 Data Collection Equipment As many parameters were required, several pieces of equipment were used to assist with field data collection, including video cameras, traffic counters, radar guns, stop watches, traffic cones, etc. Detailed info rmation (purpose and function) is shown as follows: 35

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Video Camera: to capture traffic volum e and number of vehicles in a queue Traffic Counter: to assist video camera Radar Gun: to detect operating speed on roadway Stop Watch: to obtain timing plan for intersections Traffic Cones: to set a safety zone at roadside for all obser vers and equipment Rough Measurer: to measure geometry dimension Flash Coat: to protect observ ers by reminding other drivers (a) Video camera with stand (b) Use of video camera in data collection (c) Traffic counter (d) Us e of traffic counter in data collection Figure 4.2 Data collection equipment 36

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(e) Radar gun (f ) Use of radar gun in data collection (g) Stop watch (h) Traffic cone (i) Rough measurer (j) Flash coat Figure 4.2 (Continued) 37

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4.3 Data Collection Procedures Data collection was divided into three sec tions: freeway section, exit ramp section, and crossroad section. Several kinds of data were collected for these three sections, such as traffic volume, heavy vehicles (%), operation speed, signal timing plan, number of lane changes, number of lanes, tu rn lane assignment, etc. All the data were collected at peak hours in order to capture the high volum e situation of operation. The peak hour times were to two hours for both the morning and af ternoon peaks (7:00 9:00 AM, and 4:00 6:00 PM) because of the long time of observation. Based on some data already gained, the range of peak hour time is proper due to the relatively constant traffic. For the freeway section, the hourly traffic volume of each lane was collected by video camera with the ratio of heavy vehicles, and the operation speed was collected by radar gun. The number of lane changes was also captured by video camera in the 1500 ft upstream section of the exit ramp. For the ramp section, in addition to the hour ly traffic volume of each lane, the timing plan for the ramp terminal and the queuing length for each lane at each approach was also captured. For the crossroad section, data collecti on was mainly focused on the upstream and downstream intersections. All traffic data (v olume, assignment, etc.) and timing data 38

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were collected, as most intersections were signalized. A radar gun was used to detect the operational speed of all approaches on the crossroad. Google Earth was used to collect geometric data, includi ng number of lanes, turn ba ys at intersections, lane width, curvature, median, channelized island, etc. Table 4.3 and Figure 4.3 demonstrate the comprehensive method of data collection. Table 4.3 Time period and meth od for all data collection Observing Time Parameters Methods Hourly volume of each lane and total HV ratio in freeway Counted by observer Number of lane changes on freeway in front of painted nose of exit ramp Counted by observer Hourly volume of each lane and total HV ratio in ramp terminal By video camera Queuing length of each lane in ramp terminal By video camera Signal timing and phasing at ramp terminal Read by observer using timer 7:00 to 8:00 AM or 5:00 to 6:00 PM Speed on freeway and ramp By radar gun Hourly volume of each lane and total HV ratio of each approach (downstream intersection) By video camera Queuing length of each lane in each approach (downstream intersection) By video camera Signal timing and phasing at downstream intersection Read by observer using timer Hourly volume of each lane and total HV ratio of each approach (upstream intersection) By video camera Queuing length of each lane in each approach (upstream intersection) By video camera Signal timing and phasing at upstream intersection Read by observer using timer 8:00 to 9:00 AM or 6:00 to 7:00 PM Speed on downstream and upstream intersection By radar gun 39

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Some signalized intersections were actuati ng control, whose timing plan were affected by traffic volume and might vary at each cycle. It is difficult to get the actuating timing plan from observation, because it depends on values such as minimal initial time, minimal crossing time, etc., which are difficult to know. A decision was made to simplify the observation and get a reasonable result by setting pre-timed signalized control for these intersections by using the average timing plan from actuating signal. This method had been attested to through field data. The split time for each phase was pretty close because of the relevantly constant traffic at the peak hours. Figure 4.3 Location of devices for data collection 40

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4.4 Data Reduction After data collection was completed, data reduction was conduc ted. All video camera data were read and transferred to a comput er, timing data were calculated, and data recorded on paper were input into electr onic file. Because not all field data were collected at the same time, it is reasonabl e that some data do not match. If this happened, error was controlled to less th an 5%, or data collection was conducted again until it was less than 5%. Final field data for each observed site ar e shown in Tables 44 through 4-25, which includes two directions (NB and SB, or EB and WB). 41

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Table 4.4 I-4 at Conroy Road (NB) Freeway Basic number of lanes 4 Volume of ramp 1038 Volume of each lane (from left to right) 1137, 1296, 954, 486 Exit ramp type III Number of lanes on ramp 2 Number of lane changes on freeway 72 Ramp Terminal Traffic Volume EB: 1083 WB: 801 SB: 0 NB: 1038 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 NB 16 3 1 2 EB and WB 36 3 1 Downstream Intersection Traffic Volume EB: 393 WB: 498 SB: 978 NB: 708 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 EB and WB left 14 3 1 2 EB and WB thru 14 3 1 3 SB 26 3 1 4 SB and NB thru 24 3 1 5 NB 44 3 1 Upstream Intersection Traffic Volume EB: 974 WB: 1043 SB: 603 NB: 845 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 EB and WB left 10 3 1 2 EB and WB thru 12 3 1 3 SB 15 3 1 4 SB and NB thru 26 3 1 5 NB 26 3 1 42

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Table 4.5 I-4 at Conroy Road (SB) Freeway Basic number of lanes 5 Volume of ramp 1052 Volume of each lane (from left to right) 1892,1594,1078, 696,740 Exit ramp type III Number of lanes on ramp 2 Number of lane changes on freeway 216 Ramp Terminal Traffic Volume EB: 2118 WB: 2367 SB: 1052 NB: 0 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 SB 12 3 1 2 EB and WB thru 40 3 1 Downstream Intersection Traffic Volume EB: 1083 WB: 1287 SB: 705 NB: 1116 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 EB and WB left 11 3 1 2 EB and WB thru 16 3 1 3 SB 17 3 1 4 SB and NB thru 34 3 1 5 NB 20 3 1 Upstream Intersection Traffic Volume EB: 1947 WB: 1578 SB: 0 NB: 1874 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 NB 34 3 1 2 EB left and thru 31 3 1 3 EB and WB thru 42 3 1 43

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Table 4.6 I-4 at Altamonte Drive (SB) Freeway Basic number of lanes 3 Volume of ramp 645 Volume of each lane (from left to right) 1284,1338,1257 Exit ramp type III Number of lanes on ramp 2 Number of lane changes on freeway 36 Ramp Terminal Traffic Volume EB: 1629 WB: 2271 SB: 396 NB: 0 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 SB 35 3 1 2 WB thru and left 36 3 1 3 EB and WB thru 60 3 1 Downstream Intersection Traffic Volume EB: 1578 WB: 1908 SB: 441 NB: 528 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 WB 17 3 1 2 EB and WB thru 36 3 1 3 EB 19 3 1 4 SB and NB left 17 3 1 5 SB and NB thru 21 3 1 Upstream Intersection Traffic Volume EB: 1776 WB: 1668 SB: 0 NB: 1008 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 NB 32 3 1 2 EB and WB thru 71 3 1 3 EB thru and left 28 3 1 44

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Table 4.7 I-4 at Altamonte Drive (NB) Freeway Basic number of lanes 3 Volume of ramp 1098 Volume of each lane (from left to right) 1710,1716,882 Exit ramp type III Number of lanes on ramp 2 Number of lane changes on freeway 78 Ramp Terminal Traffic Volume EB: 2655 WB: 3669 SB: 0 NB: 1728 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 NB 42 3 1 2 EB and WB thru 76 3 1 3 EB thru and left 33 3 1 Downstream Intersection Traffic Volume EB: 2258 WB: 1923 SB: 372 NB: 477 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 EB thru and left 27 3 1 2 WB thru and left 43 3 1 3 EB and WB left 20 3 1 4 SB 20 3 1 5 NB 20 3 1 Upstream Intersection Traffic Volume EB: 1878 WB: 2133 SB: 714 NB: 0 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 SB 24 3 1 2 WB thru and left 34 3 1 3 EB and WB thru 81 3 1 45

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Table 4.8 I-275 at 4th Street (SB) Freeway Basic number of lanes 4 Volume of ramp 332 Volume of each lane (from left to right) 837,868,1185,965 Exit ramp type II Number of lanes on ramp 1 Number of lane changes on freeway 126 Ramp Terminal Traffic Volume EB: 47 WB: 43 SB: 298 NB: 552 Timing and Phasing (This intersection is yield controlled, SB and NB approaches belong to main road, and EB and WB approaches belong to minor road.) Downstream Intersection Traffic Volume EB: 38 WB: 27 SB: 261 NB: 487 Timing and Phasing (This intersection is yield controlled, SB and NB approaches belong to main road, and EB and WB approaches belong to minor road.) 46

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Table 4.9 I-75 at SR 56 (SB) Freeway Basic number of lanes 2 Volume of ramp 731 Volume of each lane (from left to right) 873,767 Exit ramp type II Number of lanes on ramp 1 Number of lane changes on freeway 38 Ramp Terminal Traffic Volume EB: 674 WB: 1097 SB: 719 NB: 0 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 SB 24 3 1 2 WB left 16 3 1 3 EB and WB thru 30 3 1 Downstream Intersection Traffic Volume EB: 1095 WB: 993 SB: 734 NB: 0 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 SB left 29 3 1 2 EB left 17 3 1 3 EB and WB thru 31 3 1 Upstream Intersection Traffic Volume EB: 737 WB: 972 SB: 0 NB: 530 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 NB 21 3 1 2 EB left 17 3 1 3 EB and WB thru 27 3 1 47

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Table 4.10 I-75 at SR 56 (NB) Freeway Basic number of lanes 4 Volume of ramp 1056 Volume of each lane (from left to right) 1001,876,83 1,1113 Exit ramp type III Number of lanes on ramp 2 Number of lane changes on freeway 103 Ramp Terminal Traffic Volume EB: 978 WB: 1421 SB: 0 NB: 996 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 NB 26 3 1 2 EB left 15 3 1 3 EB and WB thru 39 3 1 Downstream Intersection Traffic Volume EB: 871 WB: 1341 SB: 16 NB: 23 Timing and Phasing (This intersection is yield controlled, EB and WB approaches belong to main road, and SB and NB approaches belong to minor road.) Upstream Intersection Traffic Volume EB: 1021 WB: 1209 SB: 767 NB: 0 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 SB 24 3 1 2 WB left 21 3 1 3 EB and WB thru 36 3 1 48

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Table 4.11 I-4 at CR 579 (WB) Freeway Basic number of lanes 3 Volume of Ramp 983 Volume of each lane (from left to right) 330,687,240 Exit ramp type II Number of lanes on ramp 1 Number of lane changes on freeway 46 Ramp Terminal Traffic Volume EB: 0 WB: 945 SB: 1250 NB: 1876 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 WB 20 3 1 2 NB and SB thru 33 3 1 3 NB thru and left 18 3 1 Downstream Intersection Traffic Volume EB: 331 WB: 64 SB: 1654 NB: 634 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 NB and SB left 12 3 1 2 NB and SB thru 24 3 1 3 EB and WB 16 3 1 Upstream Intersection Traffic Volume EB: 1184 WB: 0 SB: 1342 NB: 1653 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 EB 23 3 1 2 NB and SB thru 38 3 1 3 NB thru and left 14 3 1 49

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Table 4.12 I-4 at CR 579 (EB) Freeway Basic number of lanes 4 Volume of Ramp 1140 Volume of each lane (from left to right) 870,934,656,1240 Exit ramp type III Number of lanes on ramp 2 Number of lane changes on freeway 87 Ramp Terminal Traffic Volume EB: 1089 WB: 0 SB: 1243 NB: 1709 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 EB 28 3 1 2 NB and SB thru 42 3 1 3 NB thru and left 21 3 1 Downstream Intersection Traffic Volume EB: 351 WB: 478 SB: 1457 NB: 960 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 EB and WB 26 3 1 2 NB and SB left 19 3 1 3 NB and SB thru 37 3 1 Upstream Intersection Traffic Volume EB: 0 WB: 670 SB: 813 NB: 1534 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 WB 23 3 1 2 NB and SB thru 35 3 1 3 NB thru and left 27 3 1 50

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Table 4.13 I-275 at Ulmerton Road (SB) Freeway Basic number of lanes 3 Volume of each ramp 1784 Volume of each lane (from left to right) 654,886,704 Exit ramp type II Number of lanes on ramp 2 Number of lane changes on freeway 57 Ramp Terminal 1 Traffic Volume EB: 1194 WB: 1542 SB: 0 NB: 15 Timing and Phasing (This intersection is yield controlled; EB and WB approaches belong to main road, and NB approach belongs to minor road.) Downstream Intersection 1 Traffic Volume EB: 1023 WB: 1439 SB: 16 NB: 23 Timing and Phasing (This intersection is yield controlled, EB and WB approaches belong to main road, and SB and NB approaches belong to minor road.) Ramp Terminal 2 Traffic Volume EB: 354 WB: 0 SB: 363 NB: 225 Timing and Phasing (This intersection is yield controlled, NB and SB approaches belong to main road, and EB approach belongs to minor road.) Downstream Intersection 2 Traffic Volume EB: 379 WB: 0 SB: 371 NB: 209 Timing and Phasing (This intersection is yield controlled, NB and SB approaches belong to main road, and EB approach belongs to minor road.) 51

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Table 4.14 I-4 at SR 434 (SB) Freeway Basic number of lanes 3 Volume of ramp 1103 Volume of each lane (from left to right) 1764, 1572, 769 Exit ramp type I Number of lanes on ramp 1 Number of lane changes on freeway 76 Ramp Terminal Traffic Volume EB: 1789 WB: 1702 SB: 1021 NB: 0 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 SB left 28 3 1 2 WB thru & left 46 3 1 3 EB and WB thru 147 3 1 Downstream Intersection Traffic Volume EB: 1346 WB: 1156 SB: 346 NB: 451 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 EB and WB thru 24 3 1 2 EB thru & left 42 3 1 3 WB thru & left 19 3 1 4 SB and NB left 39 3 1 5 SB and NB thru 21 3 1 Upstream Intersection Traffic Volume EB: 1453 WB: 1134 SB: 0 NB: 987 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 NB left 22 3 1 2 EB and WB thru 46 3 1 3 NB left 19 3 1 4 EB and WB left 37 3 1 52

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Table 4.15 I-4 at SR 434 (NB) Freeway Basic number of lanes 3 Volume of ramp 1011 Volume of each lane (from left to right) 2184, 1752, 735 Exit ramp type III Number of lanes on ramp 2 Number of lane changes on freeway 96 Ramp Terminal Traffic Volume EB: 1944 WB: 1647 SB: 0 NB: 1164 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 NB left 24 3 1 2 EB and WB thru 50 3 1 3 NB left 21 3 1 4 EB and WB left 41 3 1 Downstream Intersection Traffic Volume EB: 1767 WB: 1575 SB: 198 NB: 798 Timing and Phasing 1 SB left 24 3 1 2 WB thru & left 47 3 1 3 SB left 22 3 1 4 EB and WB thru 146 3 1 Upstream Intersection Traffic Volume EB: 1797 WB: 1692 SB: 879 NB: 0 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 EB and WB thru 85 3 1 2 NB thru & left 32 3 1 3 EB and WB left 17 3 1 4 SB thru & left 17 3 1 5 EB thru & left 15 3 1 53

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Table 4.16 I-75 at Fowler Avenue (SB) Freeway Basic number of lanes 2 Volume of Ramp 1057 Volume of each lane (from left to right) 1765, 1457 Exit ramp type IV Number of lanes on ramp 2 Number of lane changes on freeway 87 Ramp Terminal Traffic Volume EB: 1579 WB: 1764 SB: 667 NB: 0 Timing and Phasing Ramp terminal is yield control. Downstream Intersection Traffic Volume EB: 1701 WB: 1879 SB: 430 NB: 391 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 EB and WB left 29 3 1 2 EB and WB thru 120 3 1 3 NB and SB left 20 3 1 4 NB and SB thru 33 3 1 Upstream Intersection Traffic Volume EB: 1684 WB: 1760 SB: 0 NB: 572 Timing and Phasing Upstream intersection is yield control. 54

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Table 4.17 I-75 at Fowler Avenue (NB) Freeway Basic number of lanes 2 Volume of Ramp 998 Volume of each lane (from left to right) 1543, 1321 Exit ramp type IV Number of lanes on ramp 2 Number of lane changes on freeway 75 Ramp Terminal Traffic Volume EB: 1589 WB: 1549 SB: 0 NB: 754 Timing and Phasing Ramp terminal is yield control. Downstream Intersection Traffic Volume EB: 1356 WB: 1305 SB: 75 NB: 0 Timing and Phasing Downstream intersection is yield control. Upstream Intersection Traffic Volume EB: 1621 WB: 1678 SB: 574 NB: 0 Timing and Phasing Upstream intersection is yield control. 55

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Table 4.18 I-4 at I-75 (SB) Freeway Basic number of lanes 2 Volume of ramp 773 Volume of each lane (from left to right) 1543, 1059 Exit ramp type I Number of lanes on ramp 1 Number of lane changes on freeway 56 Ramp Terminal Traffic Volume EB: 1734 WB: 1521 SB: 773 NB: 0 Timing and Phasing Ramp terminal is yield control. Downstream Intersection Traffic Volume EB: 1712 WB: 1671 SB: 346 NB: 0 Timing and Phasing Downstream intersection is yield control. Upstream Intersection Traffic Volume EB: 1653 WB: 1534 SB: 0 NB: 549 Timing and Phasing Upstream intersection is yield control. 56

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Table 4.19 I-4 at I-75 (NB) Freeway Basic number of lanes 3 Volume of ramp 1214 Volume of each lane (from left to right) 1987, 1552, 741 Exit ramp type IV Number of lanes on ramp 2 Number of lane changes on freeway 121 Ramp Terminal Traffic Volume EB: 1744 WB: 1529 SB: 0 NB: 621 Timing and Phasing Ramp terminal is yield control. Downstream Intersection Downstream intersection is anot her ramp of freeway, not the cross street. Furthermore, the distance is about 4750 feet, which exceeds ramp in fluence distance of 1500 feet. Therefore, ignore existence of downstream intersection. Upstream Intersection Traffic Volume EB: 1697 WB: 1492 SB: 679 NB: 0 Timing and Phasing Upstream intersection is yield control. 57

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Table 4.20 I-275 at Hillsborough Avenue (SB) Freeway Basic number of lanes 4 Volume of Ramp 831 Volume of each lane (from left to right) 1721, 1636, 1201, 698 Exit ramp type II Number of lanes on ramp 1 Number of lane changes on freeway 97 Ramp Terminal Traffic Volume EB: 1235 WB: 1198 SB: 827 NB: 0 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 SB left 22 3 1 2 WB thru & left 16 3 1 3 EB and WB thru 32 3 1 Downstream Intersection Traffic Volume EB: 1301 WB: 1279 SB: 730 NB: 491 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 EB and WB left 17 3 1 2 EB and WB thru 49 3 1 3 NB and SB left 13 3 1 4 NB and SB thru 16 3 1 Upstream Intersection Traffic Volume EB: 1284 WB: 1260 SB: 0 NB: 452 Timing and Phasing Upstream intersection is yield control. 58

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Table 4.21 I-275 at Hillsborough Avenue (NB) Freeway Basic number of lanes 3 Volume of Ramp 547 Volume of each lane (from left to right) 1641, 1410, 882 Exit ramp type II Number of lanes on ramp 1 Number of lane changes on freeway 54 Ramp Terminal Traffic Volume EB: 1389 WB: 1349 SB: 0 NB: 554 Timing and Phasing Ramp terminal is yield controlled. Downstream Intersection Traffic Volume EB: 1456 WB: 1405 SB: 75 NB: 0 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 EB and WB left 21 3 1 2 EB and WB thru 65 3 1 3 SB and NB left 19 3 1 4 SB and NB thru 26 3 1 Upstream Intersection Traffic Volume EB: 1221 WB: 1378 SB: 674 NB: 0 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 SB left 23 3 1 2 WB thru & left 17 3 1 3 EB and WB thru 41 3 1 59

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Table 4.22 I-4 at Universal Blvd. (NB) Freeway Basic number of lanes 4 Volume of Ramp 164 (HV 4%), 340 (HV 4%) Volume of each lane (from left to right) 1644 (HV 2%), 1584 (HV 3%), 1196 (HV 3%), 252 (HV 4%) Exit ramp type III Number of lanes on ramp 2 Number of lane changes on freeway 164 Ramp Terminal Traffic Volume EB: 1296 WB: 0 SB: 776 NB: 694 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 EB left and right 39 3 1 2 SB thru and left 30 3 1 3 NB thru and right 29 3 1 Downstream Intersection Traffic Volume EB: 996 WB: 1080 SB: 780 NB: 642 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 EB & WB left 15 3 1 2 EB thru and left 24 3 1 3 EB & WB thru 47 3 1 4 NB & SB left 13 3 1 5 NB & SB thru 27 3 1 Upstream Intersection Traffic Volume EB: 1296 WB: 0 SB: 1476 NB: 834 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 EB 22 3 1 2 NB & SB left 19 3 1 3 NB & SB through 42 3 1 60

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Table 4.23 I-4 at Universal Blvd. (SB) Freeway Basic number of lanes 3 Volume of Ramp 564 (HV 0%) Volume of each lane (from left to right) 1398 (HV 2%), 1404 (HV 3%), 1089 (HV 3%) Exit ramp type II Number of lanes on ramp 1 Number of lane changes on freeway 108 Ramp Terminal Traffic Volume EB: 498 WB: 765 SB: 0 NB: 396 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 NB left and right 20 3 1 2 WB thru and left 16 3 1 3 EB & WB thru 22 3 1 Downstream Intersection Traffic Volume EB: 0 WB: 741 SB: 1050 NB: 27 Timing and Phasing It is yield controlled. EB and WB are the ma jor approaches, and NB is the minor approach. Upstream Intersection Traffic Volume EB: 648 WB: 0 SB: 738 NB: 888 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 WB thru & left 39 3 1 2 NB & SB left 6 3 1 3 SB thru & left 21 3 1 4 NB & SB thu 75 3 1 61

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Table 4.24 I-4 at Lee Road (SB) Freeway Basic number of lanes 4 Volume of Ramp 894 (HV 0%) Volume of each lane (from left to right) 2262 (HV 0%), 1929 (HV 1%), 1626 (HV 0.5%), 966 (HV 0%) Exit ramp type II Number of lanes on ramp 1 Number of lane changes on freeway 54 Ramp Terminal Traffic Volume EB: 1131 WB: 909 SB: 894 NB: 0 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 SB left 33 3 1 2 EB & WB thru 62 3 1 3 WB thru and left 35 3 1 Downstream Intersection Traffic Volume EB: 1128 WB: 1357 SB: 311 NB: 0 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 SB thru & left 16 3 1 2 WB thru and left 5 3 1 3 EB & WB thru 90 3 1 4 EB thru & left 15 3 1 Upstream Intersection Traffic Volume EB: 1485 WB: 1461 SB: 0 NB: 618 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 NB left 36 3 1 2 EB thru & left 51 3 1 3 EB & WB thru 41 3 1 62

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Table 4.25 I-4 at Lee Road (NB) Freeway Basic number of lanes 4 Volume of Ramp 718 (HV 1%) Volume of each lane (from left to right) 1712 (HV 1%), 1612 (HV 1%), 1872 (HV 1%), 718 (HV 1%) Exit ramp type II Number of lanes on ramp 1 Number of lane changes on freeway 214 Ramp Terminal Traffic Volume EB: 2000 WB: 1480 SB: 0 NB: 652 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 NB left and right 15 3 1 2 EB thru and left 68 3 1 3 EB & WB thru 45 3 1 Downstream Intersection Traffic Volume EB: 1282 WB: 976 SB: 344 NB: 0 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 SB & NB left 8 3 1 2 SB & NB thru 13 3 1 3 EB thru & left 31 3 1 4 EB & WB thru 58 3 1 5 WB thru & left 13 3 1 Upstream Intersection Traffic Volume EB: 958 WB: 1024 SB: 494 NB: 0 Timing and Phasing Phase Maneuver Green (s) Yellow (s) All Red (s) 1 SB left 32 3 1 2 EB & WB thru 62 3 1 3 WB thru & left 36 3 1 63

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Chapter 5 Data Analysis and Results Field data collection provided limited data for the simulation software. Simulation models changed several parameters random ly, such as traffic volume, geometry configuration, posted speed, si gnal timing, etc. Such changes extended the simulation samples from the initial 24 to thousands of sites. Therefore, this is a very efficient and reliable method for producing a great amount of data that can develop statistical models. All results produced by CORSIM were from multi-runs (10 times). Parameters were changed within a reasonable range to enlarge the sample size. Parameter of travel time was selected for output validation (freeway section), error is controlled by 10%. Parameter of Queuing length was selected for output validation (ramp and cross road section), error is controlled by 15%. Some coefficients of driving behavior were adjusted for output validation. Table 5.1 s hows how some variables were changed, table 5.2 shows how CORSIM global parameters were adjusted, and table 5.3 shows the final calibration and validation results. Table 5.1 Change of selected variables Parameters Range Ramp Type I, II, III, IV Freeway Volume (vphpl) 100 to 2000 (100 as increment) Volume Exit Rate (%) 5% to 30% (5% as increment) No. of Through Lane on Freeway 2, 3, 4 64

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Table 5.2 Calibrated global parameters Driver Type 1 2 3 4 5 6 7 8 9 10 Driver Type Percentage (%) 17 12 12 11 10 10 9 7 7 5 Acceptable Deceleration (fpss) 21 18 15 12 9 7 6 5 4 4 Acceptable Gap Cross (s) 5.6 5.0 4.6 4.2 3.9 3.7 3.4 3.0 2.6 2.0 Acceptable Gap Left (s) 7.8 6.6 6.0 5.4 4.8 4.5 4.2 3.9 3.6 2.7 Acceptable Gap Right (s) 10.0 8.8 8.0 7.2 6.4 6.0 5.6 5.2 4.8 3.6 Table 5.3 Calibration and validation results Section Parameter Error before C. & V. Error after C. & V. Freeway Average Travel Time (s) 11.2% > 10% 8.9% Ramp & Cross Road Queuing Length (number of vehicle) 16.8% > 15% 14.6% After all data were prepared, statisti cal models, such as linear and non-linear regression, were applied to develop forecas t models for operational evaluations. All results are classified into three secti ons: freeway section, exit ramp section, and crossroad section. 5.1 Freeway Section 5.1.1 Number of Lane Changes Comparisons of the number of lane changes among the four exit ramp types are shown from Figures 5.1 to Figure 5.3. In Figure 5.1, the freeway volume is 3600 vph, 65

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the number of thru lanes on the freeway is 3, and the number of lane changes increases with the ramp volume increasi ng. In Figure 5.2, the ramp volume is 800 vph, the number of thru lanes on the freeway is 3, and the number of lane changes increases lightly with the freeway volum e increasing. In Figure 5.3, the freeway volume is 3600 vph, the ramp volume is 800 vph, and the number of lane changes increases with number of thru lanes in creasing. Thus, all the three independent variables have positive impacts on the num ber of lane changes. Under the same conditions, exit ramp type IV has the largest number of lane changes, and type I has the smallest number of lane changes. Figure 5.1 Number of lane changes vs. ramp volume 66

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Figure 5.2 Number of lane changes vs. freeway volume Figure 5.3 Number of lane changes vs. number of through lanes All simulation conditions were used to calcul ate coefficients in the prediction model. Results are shown in Table 5.4. Column B is the coefficients for all independent variables. 67

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Eq. (4) 46 52414 13 12 0XaXaXXXa Y Where, Y number of lane changes X 12 ramp type II X 13 ramp type III X 14 ramp type IV X 2 freeway volume (vph) X 3 exit rate (%) X 4 number of thru lanes on freeway Table 5.4 Coefficient values Estimate Std. Error t value Pr(>|t|) (Intercept) -2.062e+03 5.322e+01 -38.748 < 2e-16 *** x12 4.556e+02 3.009e+01 15.139 < 2e-16 *** x13 1.594e+02 3.009e+01 5.297 1.3e-07 *** x14 6.095e+02 3.009e+01 20.252 < 2e-16 *** x2 8.465e-01 1.845e-02 45.873 < 2e-16 *** x3 3.309e+01 1.246e+00 26.552 < 2e-16 *** x4 3.280e+02 1.303e+01 25.172 < 2e-16 *** Signif. codes: 0 *** 0.001 ** 0.01 * 0.05 . 0.1 1 Adjusted R-squared: 0.7327 5.1.2 Average Speed Comparisons of average speed among the four exit ramp types are shown from Figure 5.4 to Figure 5.6. In Figure 5.4, the exit rate is controlled by 20 percent, the number of thru lanes on the freeway is 3, and the average speed decreases with volume increasing. In Figure 5.5, the ramp exit rate ch anges from 5 percent to 30 percent, the 3 3 2 1aa Xaa 68

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number of thru lanes on the freeway is 3, and the average speed decreases with exit volume increasing. In Figure 5.6, the freeway volume is 800 vph, the ramp volume is 800 vph, and number of lane changes decrea ses with the number of thru lanes increasing. Thus, two independent variable s have positive impacts on the number of lane changes, while the number of thru la nes has negative impacts. Under the same conditions, exit ramp type I has the larg est average speed, and type IV has the smallest average speed. Figure 5.4 Average speed vs. volume Figure 5.5 Average speed vs. traffic exit rate 69

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Figure 5.6 Average speed vs. number of through lanes All simulation conditions were used to calcul ate coefficients in the prediction model. Results are shown in Table 5.5. Column B is the coefficients for all independent variables. Eq. (5) 46 5244 13 12 0XaXaXXaXaaY 13 2 1a Xa 3 Where, Y average speed X 12 ramp type II X 13 ramp type III X 14 ramp type IV X 2 freeway volume (vph) X 3 exit rate (%) X 4 number of thru lanes on freeway 70

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Table 5.5 Coefficient values Estimate Std. Error t value Pr(>|t|) (Intercept) 72.1402683 0.3062959 235.5 < 2e-16 *** x12 1.5794083 0.1732124 9.1 < 2e-16 *** x13 1.2224556 0.1732124 7.1 2.6e-12 *** x14 1.8364556 0.1732124 10.602 < 2e-16 *** x2 -0.0026333 0.0001062 -24.795 < 2e-16 *** x3 -0.0646289 0.0071717 -9.012 < 2e-16 *** x4 -0.4882510 0.0750032 -6.5 1.0e-10 *** Signif. codes: 0 *** 0.001 ** 0.01 * 0.05 . 0.1 1 Adjusted R-squared: 0.7653 5.1.3 Delay Time The model for delay time is similar to the number of lane changes and average speed. All simulation conditions were used to calcul ate coefficients in the prediction model. Results are shown in Table 5.6. Column B is the coefficients for all independent variables. Eq. (6) 46 5244 13 12 0XaXaXXaXaaY 13 2 1a Xa 3 Where, Y delay time (s) X 12 ramp type II X 13 ramp type III X 14 ramp type IV X 2 freeway volume (vph) X 3 exit rate (%) X 4 number of thru lanes on freeway 71

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Table 5.6 Coefficient values Estimate Std. Error t value Pr(>|t|) (Intercept) -7.482e-01 1.335e-01 -5.606 2.4e-08 *** x12 -4.273e-01 7.547e-02 -5.662 1.8e-08 *** x13 -3.844e-01 7.547e-02 -5.093 3.9e-07 *** x14 -5.274e-01 7.547e-02 -6.989 4.2e-12 *** x2 6.937e-04 4.627e-05 14.991 < 2e-16 *** x3 2.048e-02 3.125e-03 6.553 7.8e-11 *** x4 1.619e-01 3.268e-02 4.955 8.0e-07 *** Signif. codes: 0 *** 0.001 ** 0.01 * 0.05 . 0.1 1 Adjusted R-squared: 0.6929 5.1.4 Length Design for Deceleration Lane of Ramp Type I and IV For the length design of the deceleration lane, ramp type I, the speed S.D. decreases quickly when length increases, especially when the volume is high. Figures 5.7 to Figure 5.12 show the speed S.D. vs. length under different volume levels. However, for ramp type IV, this kind of change is not obvi ous. The speed S.D. decreases slowly when length increases, which means the deceleration lane does not have to be very long to lowe r speed S.D. It is also s uggested that th e length should be long if possible. 72

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Figure 5.7 Speed S.D. vs. length (type I, 2 through lanes) Figure 5.8 Speed S.D. vs. length (type I, 3 through lanes) 73

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Figure 5.9 Speed S.D. vs. length (type I, 4 through lanes) Figure 5.10 Speed S.D. vs. length (type IV, 2 through lanes) 74

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Figure 5.11 Speed S.D. vs. length (type IV, 3 through lanes) Figure 5.12 Speed S.D. vs. length (type IV, 4 through lanes) 75

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The speed S.D. should be controlled under ce rtain levels to res earch good operational performance. Simulation results are shown in Table 5.7, and si mulation results are larger than the AASHTO standard. Table 5.7 Minimum deceleration lane Operating speed (mph) AASHTO Standard (ft) Simulation Type I (ft) Simulation Type IV (ft) 55 480 750 550 60 530 800 600 65 570 850 650 70 615 875 700 75 660 900 725 5.1.5 Selection of Optimal Exit Ramp Type The exponential models show different impact s of four types of ramps on the number of lane changes, speed SD, and control delay. The larger value of coefficient ai means more contribution of independent variable to dependent variable. Based on Tables 5.4, 5, and 6, a comparison table (Table 5.8) was de veloped to show the difference. It is clear that ramp type I has the least number of lane changes out of the four types, and type IV has the largest. For speed SD, the s ituation is the opposite: ramp type IV is the best, and type I the worst. For control delay, ramp type II is the best, and type I the worst. Table 5.8 Comparisons of exit ramp types MOE Best Worst Number of Lane Changes Type I Type III Type II Type IV Standard Deviation of Speed Type IV Type II Type III Type I Control Delay per Vehicle Type II Type IV Type III Type I 76

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Because the priority ranking of ramp type fo r each parameter is totally different, it is hard to say which is the optimal type of exit ramp; the importance of the three parameters is different under different condi tions. For example, if expected exiting traffic for a ramp is very high, then the num ber of lane changes should be paid more attention in order to reduce crashes caused by decreasing lane changes. Or, in another case, if operational performance is required to strengthen, then control delay should be the first consideration. Thus, different we ights can be added to the three parameters due to different design situ ations or requirements. Taking ramp type I as the refe rence, coefficients of all other types can be compared based on the exponential model, as show n in Table 5.9. Take the second line of assigned weights (0.5 for lane change, 0.3 fo r speed SD, and 0.2 for control delay) as an example: the total value is 1 for ramp type I, 1.214 for type II, 1.057 for type III, and 1.276 for type IV. Therefore, ramp type I has the smallest value, and it is the optimal one under this condition. The comprehensive evaluation model includes three MOEs (number of lane changes, average speed, and delay time per vehicle) Different weights for each MOE are assigned for different design conditions and considerations. Finally, the optimal one can be found. It is flexible for any necessary changes. Different MOEs can be added or deleted if available. Also, weights for each MOE can be changed. 77

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Table 5.9 Selection of optimal exit ramp Ramp Type MOE Relative a i Assigned Weights Lane Change 1 0.33 0.5 0.5 0.3 0.3 0.2 0.2 I Delay Time 1 0.33 0.3 0.2 0.5 0.2 0.5 0.3 Ave. Speed -1 0.33 0.2 0.3 0.2 0.5 0.3 0.5 Total Value for I 0.33 0.6 0.4 0.6 0 0.4 0 Lane Change 1.19 0.33 0.5 0.5 0.3 0.3 0.2 0.2 II Delay Time 0.94 0.33 0.3 0.2 0.5 0.2 0.5 0.3 Ave. Speed -1.08 0.33 0.2 0.3 0.2 0.5 0.3 0.5 Total Value for II 0.35 0.6 6 0.4 6 0.6 1 0.0 1 0.3 8 -0. 02 Lane Change 1.08 0.33 0.5 0.5 0.3 0.3 0.2 0.2 III Delay Time 0.98 0.33 0.3 0.2 0.5 0.2 0.5 0.3 Ave. Speed -1.05 0.33 0.2 0.3 0.2 0.5 0.3 0.5 Total Value for III 0.34 0.6 2 0.4 2 0.6 1 -0. 01 0.3 9 -0. 02 Lane Change 1.24 0.33 0.5 0.5 0.3 0.3 0.2 0.2 IV Delay Time 0.91 0.33 0.3 0.2 0.5 0.2 0.5 0.3 Ave. Speed -1.12 0.33 0.2 0.3 0.2 0.5 0.3 0.5 Total Value for IV 0.34 0.6 7 0.4 7 0.6 -0. 01 0.3 7 -0. 04 Optimal Type I I I I IV III IV IV IV 5.2 Exit Ramp Section 5.2.1 Ramp Length Design Simulations for different conditions sugge st different minimum ramp lengths, as shown in table 5.10. Table 5.11 compares fi eld data to standard, and a red number shows field data that are shorter than standa rd. This table indicates that a short ramp length is an important problem in practical situations. Deceleration length is based on an average speed of 40 mph, and the distance is 200 ft for 50 mph and 225 ft for 60 mph. 78

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Table 5.10 Minimum ramp length No. of lanes on ramp No. of lanes on cross road No. of left turn bay Queuing length (ft) Deceleration length (ft) Perception reaction length (ft) Volume after queue (ft) Total length (ft) 1 2 0 600 175 600 330 1705 1 4 0 850 175 600 415 2040 1 6 0 950 175 600 445 2170 1 2 1 550 175 600 315 1640 1 4 1 750 175 600 380 1905 1 6 1 900 175 600 430 2105 2 4 0 700 175 600 365 1840 2 6 0 875 175 600 420 2070 2 4 1 600 175 600 330 1705 2 6 1 800 175 600 400 1975 Note: Queuing length is based on simula tion for observing sites during peak hour. 5.2.2 Ramp Configuration Speed S.D. is selected for evaluating ramp configuration. D 1 and D 2 are changed in a range to see changes of speed S.D. Taking speed S.D. as reference 1, at D 1 it is less than 400ft, and D 2 it is at a level of 1600 ft. All ot her values are compared with 1. Based on this table, the longer the distance of D 1 and D 2 would cause the smaller the value of speed S.D., and the better performance. 79

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Table 5.11 Observed ramp length No. Exit Ramp Number of ThruLanes on crossroad Ramp length (ft) 1 I-75 at State Road 56 SB 4 2575 2 I-4 at County Road 579 WB 2 1500 3 I-275 at Hillsborough Ave NB 6 910 4 I-275 at Hillsborough Ave SB 6 1100 5 I-75 at I-4 SB 6 4300 6 I-275 at 4th St SB 4 3950 7 I-4 at Universal Blvd SB 6 2665 8 I-75 at CR 581 (BBD) SB 6 2530 9 I-75 at Fowler Ave SB 6 1750 10 I-4 at Lee Road -NB 6 1770 11 I-4 at Lee Road SB 6 1840 12 I-4 at SR 434 SB 6 1000 13 I-75 at State Road 56 NB 6 2400 14 I-4 at County Road 579 EB 4 1630 15 I-4 at Universal Blvd NB 4 1630 16 I-4 at Conroy Road NB 6 3800 17 I-4 at Conroy Road SB 6 2415 18 I-4 at Altamonte Dr NB 8 1050 19 I-4 at SR 434 NB 4 1170 20 I-4 at Altamonte Dr SB 8 800 21 I-75 at CR 581 (BBD) NB 6 2600 22 I-75 at I-4 NB 6 3900 23 I-275 at Ulmerton Rd SB 4 3800 24 I-75 at Fowler AveNB 6 3800 Table 5.12 Relative speed S.D. D 1 D 2 Type A: <=400 Type B: 600 Type B: 800 Type C: >=1000 1600 1 0.954 0.910 0.865 1800 0.987 0.941 0.904 0.853 2000 0.975 0.939 0.879 0.821 80

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5.3 Crossroad Section All simulation scenarios show results of minimum distance. The design minimum distance is tested under h eavy traffic conditions, as shown in Tables 5.13 and 5.14. Table 5.13 Minimum distance between ramp terminal and downstream intersection Number of Lanes on Cross Road Distance (ft) 2 4 6 Weaving-moving across thru lanes 800 1200 1600 Transition-moving into lanes 150 U 200 R 150 U 200 R 150 U 200 R Perception-reaction distance 100 U 150 R 100 U 150 R 100 U 150 R Storage 550 (200-300) 700 (200-300) 750 (200-300) Distance to centerline of intersection 40(50) 50(50) 60(50) Total distance 1640 1740 2200 2300 2660 2760 Note: U = Urban Area, R = Rural Area. Table 5.14 Minimum distance between ramp terminal and upstream intersection Number of Lanes on Cross Road Distance (ft) 2 4 6 Transition-moving into lanes 150 U 200 R 150 U 200 R 150 U 200 R Perception-reaction distance 100 U 150 R 100 U 150 R 100 U 150 R Storage 650 (200-300) 750 (200-300) 850 (200-300) Distance to centerline of intersection 40(50) 50(50) 60(50) Total Distance 940 1040 1050 1150 1160 1260 Note: U = Urban Area, R = Rural Area. 81

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Chapter 6 Conclusions This chapter represents simulation results and mathematical models to evaluate the operational performance of exit ramps. Co mparisons are made to determine the optimal one. Ramp length and minimum dist ance on crossroads are also presented. Detailed conclusions are as follows: Numerical evaluations are provided for different ramp types on number of lane changes, average speed, and delay time. Three prediction models are presented. Minimum ramp length standard is presen ted based on analysis of speed S.D. by simulations. This standard is l onger than the traditional one. A method for selecting the optimal exit ramp type is indicated. Different weights can be added due to different purposes. Optimal is not a constant, but type III and IV are suggested when traffic volume is heavy. Minimum exit ramp length is presen ted, which includes queuing length, movement distance, etc. This dist ance helps regulate future design. Simulation for ramp configuration s hows that the longer distance between freeway and ramp terminal, and the longer distance between crossroad and exit ramp nose, the smaller the speed S.D. and the better the ramp operational performance. 82

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Minimum distance between ramp te rminal and downstream/upstream intersections was calculated. This distance standard lowers speed variance and conflict and assures traffic mobility. 83

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References Aasman, J. Modelling Driver Behaviour in Soar. Leidschendam, The Netherlands: KPN Research, 1995. Abdel-Aty, Mohamed, Jeremy Dilmore, and Albinder Dhindsa. Evaluation of Variable Speed Limits for Real-time Freeway Safety Improvement. Accident Analysis and Prevention, 38, 2006, pp. 335-345. Abdel-Aty, Mohamed, and Yile Huang. Explor atory Spatial Analysis of Expressway Ramps and its Effect on Route Choice. Journal of Transportation Engineering 2004. Ahmed, K. I., M. E. Ben-Akiva, H. N. Kout sopoulos, and R. G. Mishalani. Models of Freeway Lane Changing and Gap Accepta nce Behavior. In J.-B. Lesort (Ed.), Transportation and Traffic Theory New York: Elsevier Science Publishing, 1996. American Association of State Highway a nd Transportation Officials. A Policy on Geometric Design of Highways an d Streets. Washington, D.C., 2004. Bared, Joe, Alvin Powell, Evangelos Kaisar, and Ramanujan Jagannathan. Crash Comparison of Single Point and Ti ght Diamond Interchanges Sources. Journal of Transportation Engineering May 2005, pp. 379-381. Bared, Joe, Greg L. Giering, and Dave y L. Warren. Safety of Evaluation of Acceleration and Deceleration Lane Lengths. ITE Journal May 1999, pp. 50-54. Batenhorst, Ralph A., and Je f G. Gerken. Operational Analysis of Terminating Freeway Auxiliary Lanes with One-Lane and Two-Lane Exit Ramps: A Case Study. Mid-Continent Transportation Symposium Proceedings 2000. Bauer, K. M., and D.W. Harwood. Statisti cal Models of Accidents on Interchange Ramps and Speed-Change Lanes. FHWA-RD-97-106, FHWA, U.S. Department of Transportation, 1998. Bernhardt, Kristen L. Sanford, and Mark R. Virkler. Improving the Identification, Analysis and Correction of High-Crash Locations. ITE Journal 2002. 84

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About the Author Mr. Linjun Lu has a solid background in tr ansportation engineer ing. He got his bachelors and masters degrees from the Department of Transportation Engineering, Southeast University (Nanjing China), and he will complete his P h.D. in the Spring of 2011 at the Department of Ci vil & Environmental Engineering at the University of South Florida in Tampa. He has over six years of experience in research and application projects in transportation engineering. Hi s research and work areas mainly include safety and operation analysis, traffic management and c ontrol, simulations, traffic planning, etc. Specifically, he is experienced in safety and operational analysis. He is also familiar with field observation, cras h and conflict analysis, dr iving behavior analysis, modeling, and countermeasures and evaluations Furthermore, he can operate Safety Analyst (software) as an assistant for safety design and is skilled in VISSIM, CORSIM, SYNHCRO, HCS, AUTOCAD, and SPSS.


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ABSTRACT: This research focuses primarily on the analysis of exit ramp performance related to safety and operations. The safety analysis focuses on the impacts of different exit ramp types for freeway diverge areas and different factors contributing to the crashes that occur on the exit ramp sections. The operational analysis is based mainly on simulations by TSIS-CORSIM. Different ramp effects and guidance for selecting optimal exit ramp type are concluded. Issues related to ramp sections and crossroad sections are also demonstrated. Minimum ramp length and minimum distance between ramp terminal and downstream or upstream intersections are calculated. The operational analysis was conducted to determine different ramp effects and to provide guidance for selecting optimal exit ramp type. Comparisons of the operational performance of different types of exit ramps are made to present a method for choosing the optimal one. Some methods of evaluation (MOEs) are used to approach this objective, such as number of lane changes, average speed, delay time, etc. Data collection at 24 sites in Florida was conducted, and traffic simulations by TSIS-CORSIM were applied for analysis. Mathematical models were built to evaluate different impacts of these ramps based on simulations. All impact analysis is concluded to summarize a model for optimal exit ramp selection. In addition to ramp type evaluation and selection, issues related to ramp section and crossroad section are demonstrated. Minimum ramp length and minimum distance between ramp terminal and downstream or upstream intersections are calculated.
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