VASTO – Evolutionary Agent System for Transportation Outlook

Agent-Based Modeling and Simulation in 

the Dilemma Zone

Federal Highway Administration

Publication No.: FHWA-HRT-15-082

Research, Development, and Technology

Turner-Fairbank Highway Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

Exploratory Advanced Research Program
Foreword

Gaining an indepth understanding of drivers’ decisions and behaviors in dilemma zone situations will 

help State, county, and city transportation agencies to develop and deploy effective 

countermeasures to improve safety and reduce potential crashes at signalized intersections. This 

study’s objective is to develop a dilemma zone behavior model that considers the effects on drivers 

of certain factors found at signalized intersections, such as the presence of a pedestrian countdown 

signal, the presence of a red-light photo enforcement camera, and the actions of an adjacent vehicle.

Federal Highway Administration’s (FHWA’s) Highway Driving Simulator was used to collect drivers’ 

responses as a function of speed limit and whether the driver was in a hurry. A dilemma zone 

behavior model was developed based on data collected in the driving simulation experiments via 

agent-based modeling and simulation. Results from the experiments suggested that sufficient 

external information, such as the presence of a red-light photo enforcement camera, can accurately 

predict the drivers’ decisions when they were confronted with the dilemma zone. The dilemma zone 

behavior model also takes into account the interactions between vehicles and provides realistic 

predictions of driver behaviors under various traffic conditions.

Monique R. Evans

 Director, Office of Safety

Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest 

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i

Technical Report Documentation Page

1. Report No.

FHWA-HRT-15-082

2. Government Accession No. 3. Recipient’s Catalog No.

4. Title and Subtitle

Agent-Based Modeling and Simulation in the Dilemma Zone

5. Report Date

December 2015

6. Performing Organization Code: 

7. Author(s)

Sojung Kim, Young-Jun Son, Mary Anne Jeffers, Jason 

Williams, Yi-Chang Chiu

8. Performing Organization Report No. 

9. Performing Organization Name and Address

University of Arizona, Tucson, AZ 85721

George Mason University, Fairfax, VA 22030

Leidos, Reston, VA 20190

Textron Systems/AAI Corporation, Hunt Valley, MD, 21030

10. Work Unit No.

11. Contract or Grant No.

12. Sponsoring Agency Name and Address

Federal Highway Administration

Office of Safety Research and Development

6300 Georgetown Pike

McLean, VA 22101

13. Type of Report and Period Covered

Final Report

14. Sponsoring Agency Code

HRDS-30

15. Supplementary Notes

FHWA Contracting Officer’s Representative (COR): Dr. C. Y. David Yang

16. Abstract

The goal of this study is to develop a realistic dilemma zone (DZ) model that considers the effects of factors 

surrounding vehicles at an intersection, particularly focusing on driver decisionmaking behavior, such as the 

presence of a pedestrian countdown signal, a red-light photo enforcement camera, and the actions of an adjacent 

vehicle. The Federal Highway Administration’s Highway Driving Simulator (HDS) was used to collect drivers’ 

responses as a function of facility speed limit and whether the driver was in a hurry. From these responses, a DZ 

model was developed via agent-based modeling and simulation (ABMS) under the extended belief-desire-intention 

(E-BDI) framework. This framework represents uncertain perception and decision behaviors of humans in a 

probabilistic manner. To demonstrate and validate the proposed approach, the drivers’ actions under two 

circumstances were compared: (1) drivers only knew the approach speed and distance to the stop (i.e., internal 

information); and (2) drivers knew the internal information as well as external information, such as presence of a 

pedestrian countdown signal or presence of a red-light photo enforcement camera, and the behavior of an 

adjacent vehicle. The experiments indicate that sufficient external information could accurately predict the 

decisions of drivers and thus reduce the number of red-light violations that could potentially cause accidents at an 

intersection. In addition, the proposed E-BDI-based DZ model allowed us to consider the physical interactions 

between vehicles such that it provides realistic prediction results of drivers under various traffic conditions.

17. Key Words

dilemma zone, driving simulator, time pressure, driving 

in a hurry, red light photo enforcement camera, 

pedestrian countdown signal, adjacent vehicle, red-light 

running

18. Distribution Statement

No restrictions. This document is available to the public through the 

National Technical Information Service, Springfield, VA 22161.

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

48

22. Price

N/A

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
ii

Table of Contents

1 Executive Summary.................................................................................................................. 1

2 Introduction.............................................................................................................................. 3

3 Overview of Research Methodology........................................................................................ 5

4 DZ Data Collection Using a Highway Driving Simulator........................................................... 7

4.1 Method............................................................................................................................. 7

4.1.1 Experimental Design ................................................................................................. 7

4.1.2 Simulation ................................................................................................................. 8

4.1.3 Highway Driving Simulator ..................................................................................... 16

4.1.4 Participants............................................................................................................. 17

4.1.5 Procedures.............................................................................................................. 17

4.1.6 Instructions............................................................................................................. 18

4.2 Results............................................................................................................................ 19

4.2.1 Influence of Motion Base........................................................................................ 19

4.2.2 Driver Performance Measures................................................................................ 19

4.2.3 Post-Participation Questionnaire ........................................................................... 23

5 Analysis Results...................................................................................................................... 27

5.1 ABMS Scenario ............................................................................................................... 27

5.1.1 DZ Model................................................................................................................. 27

5.1.2 E-BDI Framework .................................................................................................... 27

5.2 ABMS Model Calibration and Validation........................................................................ 28

5.2.1 Calibration of BBN................................................................................................... 28

5.2.2 Calibration of EDFT ................................................................................................. 30

5.3 Modeling Experiments................................................................................................... 31

5.3.1 Low-Facility Speed Limit ......................................................................................... 32

5.3.2 High-Facility Speed Limit......................................................................................... 34
iii

5.4 Discussions..................................................................................................................... 37

6 Concluding Remarks............................................................................................................... 39

7 References.............................................................................................................................. 41

Appendix A. Post-Participation Survey ......................................................................................... 43
iv

List of Figures

Figure 4-1: Image. Intersection indicating where pedestrians crossed.......................................... 9

Figure 4-2: Photograph. Driving simulator used for the study..................................................... 16

Figure 4-3: Chart. Predicted probability of proceeding through a DZ intersection by degree of 

driving in a hurry and drive number. ............................................................................................ 21

Figure 4-4: Chart. Predicted probability of proceeding through a DZ intersection by presence of 

a red-light photo enforcement camera and drive number. ......................................................... 22

Figure 4-5: Chart. Percentage of participants who selected each factor that affected their 

decisions to run a red light in the real world................................................................................ 26

Figure 5-1: Image. Screenshot of simulation................................................................................ 27

Figure 5-2: Chart. Path model in SEM analysis. (9)......................................................................... 29

Figure 5-3: Chart. BBN for E-BDI framework. (9)............................................................................ 30

Figure 5-4: Equation. EDFT used in the DZ. (9)............................................................................... 31

Figure 5-5: Chart. SD diagram of Group A (RedLightCam=no and PedCountSig=no). (9).............. 32

Figure 5-6: Chart. SD diagram of Group A (RedLightCam=yes and PedCountSig=yes). (9)............ 33

Figure 5-7: Chart. SD diagram of group D (RedLightCam=no and PedCountSig=no). (9)............... 35

Figure 5-8: Chart. SD diagram of group D (RedLightCam=yes and PedCountSig=yes). (9)............ 35
v

List of Tables 

Table 4-1: Order I description by scenario ID, signal phase, and values for independent 

factors. (9)....................................................................................................................................... 11

Table 4-2: Order II description by scenario ID, signal phase, and values for independent 

factors. (9)....................................................................................................................................... 12

Table 4-3: Order III description by scenario ID, signal phase, and values of independent 

factors. (9)....................................................................................................................................... 13

Table 4-4: Order IV description by scenario ID, signal phase, and values of independent 

factors. (9)....................................................................................................................................... 14

Table 4-5: Wald Type III statistics for GEE analysis of the probability of proceeding through a DZ 

intersection regarding the different design factors. .................................................................... 20

Table 4-6: Distribution of how often participants recalled other drivers running red lights in the 

real world (based on their respective definition of red-light running). ....................................... 25

Table 4-7: Distribution of how often participants recalled themselves running red lights in the 

real world (based on their respective definition of red-light running). ....................................... 25

Table 5-1: Standardized regression weights of driver groups. (9)................................................. 29

Table 5-2: Weight vector of driver groups.................................................................................... 31

Table 5-3: Summary of experiments (group A: 90 percent; group B: 10 percent)....................... 33

Table 5-4: Summary of experiments (group A: 10 percent; group B: 90 percent)....................... 34

Table 5-5: Summary of experiments (group C: 90 percent; group D: 10 percent)....................... 37

Table 5-6: Summary of experiments (group C: 10 percent; group D: 90 percent)....................... 37
vi

List of Abbreviations and Symbols

ABMS Agent-based Modeling and Simulation

BBN Bayesian Belief Network

CD/M2Candela per Square Meter

CI Confidence Interval

DZ Dilemma Zone

E-BDI Extended Belief-Desire Intention

EDFT Extended Decision Field Theory

fL Foot-lambert

GEE Generalized Estimating Equations

HDS Highway Driving Simulator

ITE Institute of Traffic Engineers

KM/H Kilometers per Hour

MI/H Miles per Hour

NHTSA National Highway Traffic Safety Administration

PRT Perception-Reaction Time

SEM Structural Equation Modeling

S-D Speed-Distance

1

1 Executive Summary

The dilemma zone (DZ) is an area in which a driver cannot stop gently before the stop line or 

clear the intersection safely before the red phase. (1) When decisions are made in the DZ, there 

could be a risk of a car crash, such as a rear end or right-angle crash. To mitigate the risk 

inherent in the DZ, many researchers have attempted to identify critical factors and develop a 

driver decisionmaking model. (1) The purpose of this study is to develop a realistic DZ model that 

considers the effects of surrounding factors at an intersection. The factors examined in the 

assessment of the influence of the road environment on driver decisionmaking behavior within 

the DZ simulation were: 

 Facility speed limit of the roadway (FacilitySpeed): Possible speed limits included 40 

miles per hour (mi/h) (64.37 kilometers per hour (km/h)) and 55 mi/h (88.51 km/h). 

Each participant performed three drives, and each drive had the same posted speed 

limit.

 Degree of driving in a hurry (InAHurry): Half of the participants were tasked to finish 

their drives within the expected completion time (18.5 minutes for the 55 mi/h (88.51 

km/h) group and 22.5 minutes for the 40 mi/h (64.37 km/h) group).

 Presence of a red-light photo enforcement camera at the intersection (RedLightCam): 

Red-light photo enforcement cameras were simulated at four of the DZ intersections 

and eight of the non-DZ intersections. 

 Presence of a pedestrian countdown signal at the intersection (PedCountSig): Pedestrian 

countdown signals were simulated at four of the DZ intersections and eight of the nonDZ intersections.

 Behavior of an adjacent vehicle as the participant approaches the intersection 

(AdjVehBeh): An adjacent vehicle in the left lane (participant was in the right lane) was 

simulated for all DZ intersections and eight of the non-DZ intersections. The adjacent 

vehicle stopped at four of the DZ intersections and proceeded through the other four. 

Participants were separated into four groups based on the facility speed limit and the degree of 

driving in a hurry. The four groups were: (1) group A had a 40 mi/h speed limit and did not drive 

in a hurry; (2) group B had a 40 mi/h speed limit and drove in a hurry; (3) group C had a 55 mi/h 

speed limit and did not drive in a hurry; and (4) group D had a 55 mi/h speed limit and drove in 

a hurry. 

The Federal Highway Administration’s Highway Driving Simulator (HDS) was used to conduct 

experiments with licensed drivers (i.e., residents of the Washington, DC, metropolitan area, 

which includes the District of Columbia, southern Maryland, and Northern Virginia). The HDS 

used a late model compact car chassis providing acceleration, deceleration, handling, and 

braking functions, along with all audio (e.g., driving noise) and a 210-degree horizontal highresolution visual scene. The experimental scenarios had 24 signalized intersections, 8 of which 

had signal changes intended to produce a DZ. 
2

Ninety-nine licensed drivers provided useable data, 48 females (mean age 46 years, range 18–

80) and 51 males (mean age 47 years, range 19–82). 

Generalized estimating equations (GEE) with a binomial response distribution and logit link 

function were used to assess whether the probability of proceeding through a DZ intersection 

varied regarding the five factors (FacilitySpeed, InAHurry, RedLightCam, PedCountSig, and

AdjVehBeh). The results showed that all factors influenced the drivers’ decisions. Participants in 

the 40 mi/h (64.37 km/h) speed condition had a higher probability of continuing through a DZ 

intersection than those in the 55 mi/h (88.51 km/h) speed condition. The probability of 

proceeding through a DZ intersection was greater for participants who were not tasked to drive 

in a hurry than for participants who were driving in a hurry. In addition, the probability of 

proceeding through a DZ intersection without a red-light photo enforcement camera increased 

across all drivers. The absence of a pedestrian countdown signal also increased the likelihood 

that participants continued through a DZ intersection. When an adjacent vehicle traveled 

through the intersection, participants were also more likely to proceed through a DZ 

intersection. 

From these driver response findings in the HDS, a DZ model was developed via ABMS under the 

E-BDI framework, which represents the perception and decisionmaking behaviors of humans 

regarding an uncertain property by using probabilistic models.

(2) Four types of E-BDI-based DZ 

models were classified by the facility speed limit and the degree of being in a hurry. E-BDIbased DZ models were calibrated with two hypothetical constructs: internal information and 

external information. Internal information includes variables that depend on the vehicle’s 

approach speed (AppSpeed) and distance to the stop line (Distance), as set forth in the Institute 

of Traffic Engineers’ (ITE) DZ model. External information includes three environmental factors, 

i.e., RedLightCam, PedCountSig, and AdjVehBeh. Because both hypothetical attributes were 

unobserved during the experiments, i.e., they were latent variables, a structural equation 

modeling (SEM) approach was used to analyze the relative contributions of internal and 

external attributes on drivers’ decisions in a DZ. The results of the SEM were used to calibrate 

the E-BDI framework (i.e., E-BDI-based DZ model). Thus, the E-BDI-based DZ model was able to 

represent stopping and proceeding decisions of drivers from external and internal information.

The ABMS with E-BDI-based DZ model depicts the impact of external and internal information

via a speed-distance (SD) diagram. In ABMS, driver agents’ stopping and proceeding decisions at 

the onset of the yellow phase were counted to create SD diagrams under different 

configurations of intersections. The results showed that the presence of a pedestrian 

countdown signal or a red-light photo enforcement camera mitigates the number of red-light 

violations. According to the post-participation survey of the drivers, drivers were able to predict 

the time of the traffic signal change via the remaining time of the pedestrian countdown signal 

so that they could make a clear decision at the intersection. In addition, when drivers were 

uncertain of their decisions, they followed the decisions of adjacent vehicles or tried to stop if a 

red-light photo enforcement camera existed on a roadway.
3

2 Introduction

For decades, driving safety has been a major concern in the traffic management domain 

because car accidents not only affect the performance of the traffic system but also inflict huge 

damage in terms of deaths and major injuries to humans. According to the National Highway 

Traffic Safety Administration (NHTSA), 23 percent of the 29,757 fatal crashes in the United 

States in 2012 were crashes related to intersections.(3) This is because a driver at an 

intersection needs to consider multiple options (e.g., stop, proceed, turn right, and turn left) 

with respect to the traffic situation within a short amount of time. (4) Therefore, many studies 

related to driving safety have focused on drivers’ behaviors at an intersection, aiming to reduce 

the risk of car crashes. One major concept is the dilemma zone (DZ), which is an area in which a 

driver cannot stop safely before the stop line or clear the intersection safely before the red 

phase.

(1) Whatever decision is made in the DZ, there could be a risk of a car crash, such as a rear

end or right-angle collision.

To reduce the risk inherent to the DZ, ITE recommended a DZ model (or Type I DZ) based on the 

approaching speed and distance to the stop line of a vehicle. (1) The Type I DZ is used to detect 

the DZ (xdz) if the vehicle’s approaching speed (V0) to an intersection is already known. The goal 

of the Type I DZ is to minimize the DZ by controlling the length of the yellow phase so that a 

driver can choose either to proceed or stop at the onset of the yellow phase (i.e., option zone).

In the Type I DZ, the DZ (xdz) is detected by subtracting the minimum stopping distance (xc) from 

the maximum yellow passing distance (x0) at the onset of the yellow phase. To compute the 

minimum stopping distance (xc) and the maximum yellow passing distance (x0), the Type I DZ 

model includes the following factors: the approaching speed of the vehicle (V0), the maximum 

deceleration rate when stopping (a2), the maximum acceleration rate when proceeding (a1), the 

perception-reaction time of the driver (PRT) for proceeding (δ1) and stopping (δ2), the length of 

the yellow phase (τ), the width of the intersection (w), and the average vehicle length (L). 

Nonetheless, due to the uncertainty of the human reasoning process, car crashes still occur, 

even when a driver is in the option zone. To study the uncertainty in driver decisions, a Type II 

DZ has been proposed, which considers the stopping probability of drivers at the onset of the 

yellow phase. (5) This approach defines the DZ as being from the position at which 90 percent of 

drivers stop to the position at which 10 percent of drivers stop, so that the uncertainty aspect 

of driver decisions can be covered. Similar to the Type I DZ, the Type II DZ can be eliminated by 

controlling the length of the yellow phase. However, because the Type II DZ focuses only on the 

results of observations (i.e., stopping and proceeding) without considering the factors that 

impact driver decisions, controlling the length of the yellow phase is considered the only way to 

minimize the number of car crashes caused in the Type II DZ. This focus means that the Type II 

DZ model is difficult to handle in the case in which drivers are affected by other factors, such as 

traffic conditions.

Drivers’ behaviors are affected by the surrounding environment, such as other vehicles’ 

movements or intersection conditions. 
4

In a DZ, the drivers’ decisions are also influenced not only by their own condition (e.g., 

approaching speed and distance to the stop line of a vehicle) but also by the surrounding 

environment at an intersection. Gates et al. (6) claimed that the actions of vehicles in an adjacent 

lane affect drivers’ decisions in the DZ. Huey and Ragland (7)similarly showed that the

pedestrian countdown signal made drivers’ behaviors more conservative (i.e., less likely to 

enter the intersection at the end of the yellow phase). A red-light photo enforcement camera is 

also known to be useful to mitigate red-light running by vehicles, thereby reducing the 

possibility of car crashes. (8)

Therefore, in this study, we developed a new DZ model that includes the effects of three 

surrounding factors (i.e., presence of a pedestrian countdown signal, presence of a red-light 

photo enforcement camera, and behavior of an adjacent vehicle) in addition to factors such as 

the subject vehicle’s approaching speed and distance to the stop line given by the Type I DZ 

model. The driver’s decision model is then developed by ABMS under the E-BDI framework, 

which is able to represent the uncertain decisionmaking behavior of drivers via probabilistic 

inference algorithms such as the Bayesian belief network.

(9) (2)
5

3 Overview of Research Methodology

Our research efforts focused on two elements: (1) collecting human behavioral data via a 

driving simulator, and (2) modeling and analysis.

While collecting human behavioral data via a driving simulator, our first goal was to develop an

experimental plan, which helps to understand the individual and interactive impacts of factors 

on output results with minimal experimental and systematic error. (10) The goal was to capture 

driver behavior in the DZ under a variety of conditions. An experimental plan was developed in 

collaboration with the University of Arizona, Leidos, and AAI, where the factors considered 

include the (1) facility speed limit of the roadway (FacilitySpeed), (2) degree of driving in a hurry 

(InAHurry), (3) presence of a red-light photo enforcement camera (RedLightCam), (4) presence 

of a pedestrian countdown signal (PedCountSig), and (5) behavior of an adjacent vehicle as the 

participant approaches the intersection (AdjVehBeh). The University of Arizona, in collaboration 

with researchers at AAI and Leidos, developed a simulation work plan that was used to collect 

human behavior data when encountering intersections via a driving simulator at Federal 

Highway Administration’s Turner-Fairbank Highway Research Center. More details about the 

simulation work plan can be found in section 4, and a video of the driving simulator is available 

at https://www.youtube.com/watch?v=vrJiVJaZW4g.

(11)

The responses of participants in the driving simulation experiment were used to develop an 

ABMS under the E-BDI framework (see section 5.1.2). In addition to the five factors previously 

mentioned, two factors provided by the ITE DZ model were considered: a vehicle’s approaching 

speed (AppSpeed), and a vehicle’s distance to the stop line (Distance). More details of the 

experiment design can be found in section 5.

In terms of modeling and analysis, our first goal was to identify the essential factors relevant to 

drivers’ decisionmaking and to mimic their behavior when running into a yellow phase at 

intersections. To this end, an analysis of the DZ was conducted based on the responses of 

participants in the driving simulation experiment. Generalized estimating equations (GEE) with 

a binomial response distribution and logit link function were used to assess whether the 

probability of proceeding through a DZ intersection varied with respect to the five factors (i.e., 

FacilitySpeed, InAHurry, RedLightCam, PedCountSig, and AdjVehBeh). The second goal was to 

develop a DZ simulation model where drivers’ decisionmaking behaviors are represented in the 

E-BDI framework. (1) (12) In addition to the five factors previously mentioned, two factors 

provided by the ITE DZ model were also considered, AppSpeed and Distance. To test the impact 

of these factors on drivers’ proceeding behavior when encountering a DZ, several microscopic 

traffic simulation experiments were conducted based on the constructed and validated ABMS

model. More details of this work can be found in section 5.

7

4 DZ Data Collection Using a Highway Driving 

Simulator

4.1 Method

4.1.1 Experimental Design

There were five design factors in this study: (1) facility speed limit, (2) degree of driving in a 

hurry, (3) presence of a red-light photo enforcement camera, (4) presence of a pedestrian 

countdown signal, and (5) presence and behavior of an adjacent vehicle. Each design element is 

discussed in more detail below. For DZ intersections, the facility speed limit and degree of 

driving in a hurry were between-group factors, while the presence of a red-light photo 

enforcement camera, presence of a pedestrian countdown signal, and behavior of an adjacent 

vehicle were within-group factors. 

 Facility speed of the roadway (FacilitySpeed): The two speed limits were 40 mi/h (64.37 

km/h) and 55 mi/h (88.51 km/h). All drives completed by a participant had the same 

posted speed limit.

 Degree of driving in a hurry (InAHurry): Half of the participants were tasked to drive in a 

hurry (as described in section 4.1.6). However, there was no change in the simulation 

between those tasked with driving in a hurry and those not tasked with driving in a 

hurry. All drives completed by a participant had the same degree of hurried driving.

 Presence of a red-light photo enforcement camera at the intersection (RedLightCam): 

Red-light photo enforcement cameras were simulated at four of the DZ intersections 

and eight of the non-DZ intersections. The intersections with an enforcement camera 

were appropriately signed (one 500 feet in advance of the intersection and one at the 

intersection).

 Presence of a pedestrian countdown signal at the intersection (PedCountSig): Pedestrian 

countdown signals were simulated at four of the DZ intersections and eight of the nonDZ intersections. Three to five simulated pedestrians crossed or prepared to cross in 

each direction on the near crosswalk at both of the forced red phase intersections and 

two of the forced green phase intersections. Pedestrians were included to make the 

simulation appear more realistic to the driver and to mimic the possible threat of 

pedestrians at the DZ intersections.
8

 Behavior of an adjacent vehicle as the participant approaches the intersection 

(AdjVehBeh): An adjacent vehicle in the left lane (participant was in the right lane) was 

present for all DZ intersections and eight of the non-DZ intersections. The vehicle first 

turned onto the simulated roadway from a left midblock side entrance. It accelerated to 

overtake the participant’s vehicle and maintained a one-car-length lead on the 

participant’s vehicle until the next signal. 

The vehicle stopped at four of the DZ intersections and proceeded through the other 

four. If the vehicle was supposed to stop, then it slowed, and the brake lights were 

simulated 1 second after the onset of the yellow phase. The adjacent vehicle never 

changed lanes and, in all cases, would turn off at the next midblock location following 

the green phase of the intersection. In addition, for non-DZ intersections, the presence 

of an adjacent vehicle was manipulated to expose participants to similar road conditions 

between DZ and non-DZ intersections. Thus, participants would not know whether they 

are at DZ intersections or not. 

In addition to the aforementioned five factors, oncoming left-turn traffic was considered at 

eight of the non-DZ green phase intersections to make the simulation appear more realistic to 

the driver and to mimic the possible threat of a left-turning vehicle at the DZ intersections (in 

fact, there was no left-turning vehicle at the DZ intersections). Three or four vehicles were 

queued in the turn lane, with the first vehicle 328.08 feet (100.00 m) away from the 

intersection. The first vehicle started to move when the participant was 21 seconds away from 

the intersection. Each successive vehicle started to travel through the intersection 12 seconds

after the preceding one. Oncoming traffic traveled, on average, at a rate of 40 mi/h (64.37 

km/h). Depending on how fast the participant drove, all, some, or none of these other vehicles 

passed through the intersection. The oncoming traffic turned in the presence of the driver, but 

did not interact with the driver in any way.

There are four groups specified by the between-group factors: (1) facility speed limit, and (2) 

degree of driving in a hurry. (9) The posted speed limit for groups A and B was 40 mi/h, and the 

posted speed limit for groups C and D was 55 mi/h. Participants in groups A and C drove as they 

normally would, and those in groups B and D drove in a hurry. A payoff matrix was used to 

motivate participants to drive in a hurry (see section 4.1.6). The manipulation of the 

within-group factors is discussed in more detail in section 4.1.2.

4.1.2 Simulation

The simulation consisted of a four-lane roadway (two lanes in each direction) with signalized 

intersections present every 0.6 mi (0.97 km). There was also a left turn lane for each direction 

of travel. Each lane was 12 feet (3.66 meters) wide. 
9

The total intersection width (from stop bar to stop bar, including crosswalks, shoulders, curbs, 

and sidewalks) was 193.55 feet (58.99 meters). The aforementioned configuration of the 

simulated intersection is shown in Figure 4-1,where from each direction the short white line 

represents the stop bar and the two longer white lines delineate the two sides of the crosswalk. 

The total mileage was approximately 14.5 mi (23.34 km) and the simulated environment 

resembled a suburban commercial area. Assuming participants would comply with the speed 

limit, for those participants who had a 40-mile-per-hour speed limit, the drive was 

approximately 22 minutes long without traffic signals and signal compliance (i.e., no stopping 

while driving). For those participants with a 55-mile-per-hour speed limit, the drive was 

approximately 16 minutes long, without traffic signals and signal compliance.

© AAI

Figure 4-1: Image. Intersection indicating where pedestrians crossed.

The posted speed limit follows the facility speed limit based on the group assignment, as stated 

in section 4.1.1 (i.e., 40 mi/h or 55 mi/h). Speed limit signs were posted once every three 

intersections in the simulation.
10

To make all participants maintain the posted speed limit, the driver of a vehicle going 8 mi/h 

over the speed limit received a speeding ticket ($0.50) after that participant’s drive (see section 

4.1.6). There were 24 intersections in each drive. Eight of the intersections presented a DZ, and 

the remaining 16 intersections did not. Of the 16 non-DZ intersections, 2 were set to the red 

phase for all participants and the rest remained green throughout. The order of the 24 

intersections within a drive was pseudorandom, and there were 4 different scenario orders 

(order I–order IV). 

Table 4-1,

(9) Table 4-2,(9) Table 4-3,(9) and Table 4-4(9) outline order I, order II, order III, and 

order IV, respectively. One of the orders was randomly selected for each participant and the 

experiment was conducted according to the selected order. Therefore, the order of the 

intersections was different for each participant, but for any one participant, the same order was 

used for his or her drives. Within each of the groups (A–D), 6 of the 24 participants received 

each order (I, II, III, or IV). The same four scenario orders were replicated with the two speed 

limits (40 mi/h and 55 mi/h) for a total of eight different simulation designs.
11

Table 4-1: Order I description by scenario ID, signal phase, and values for independent 

factors.

(9)

Position Scenario 

ID

Signal 

Phase

Redlight 

camera

Pedestrian 

Countdown 

Signal

Adjacent 

Vehicle

Oncoming 

Left-Turn 

Traffic

1 12 Green Yes Yes (no Peds) No Yes

2 18 Red No Yes (with Peds) Stop No

3 4 Dilemma No No Stop No

4 13 Green Yes No Go No

5 2 Dilemma Yes No Stop No

6 23 Green No No No Yes

7 9 Red Yes Yes (with Peds) Stop No

8 5 Dilemma Yes Yes Go No

9 19 Green No Yes (no Peds) No Yes

10 16 Green Yes No No Yes

11 22 Green No No Go No

12 7 Dilemma No Yes Go No

13 20 Green No Yes (with Peds) No No

14 10 Green Yes Yes (no Peds) Go Yes

15 1 Dilemma Yes Yes Stop No

16 21 Green No No Go Yes

17 3 Dilemma No Yes Stop No

18 15 Green Yes No No No

19 17 Green No Yes (no Peds) Go Yes

20 11 Green Yes Yes (with Peds) No No

21 8 Dilemma No No Go No

22 24 Green No No No No

23 6 Dilemma Yes No Go No

24 14 Green Yes No Go Yes
12

Table 4-2: Order II description by scenario ID, signal phase, and values for independent 

factors.

(9)

Position Scenario 

ID

Signal 

Phase

Redlight 

camera

Pedestrian 

Countdown 

Signal

Adjacent 

Vehicle

Oncoming 

Left-Turn 

Traffic

1 16 Green Yes No No Yes

2 9 Red Yes Yes (with Peds) Stop No

3 7 Dilemma No Yes Go No

4 19 Green No Yes (no Peds) No Yes

5 5 Dilemma Yes Yes Go No

6 23 Green No No No Yes

7 22 Green No No Go No

8 3 Dilemma No Yes Stop No

9 20 Green No Yes (with Peds) No No

10 10 Green Yes Yes (no Peds) Go Yes

11 21 Green No No Go Yes

12 1 Dilemma Yes Yes Stop No

13 24 Green No No No No

14 11 Green Yes Yes (with Peds) No No

15 6 Dilemma Yes No Go No

16 17 Green No Yes (no Peds) Go Yes

17 8 Dilemma No No Go No

18 15 Green Yes No No No

19 14 Green Yes No Go Yes

20 12 Green Yes Yes (no Peds) No Yes

21 2 Dilemma Yes No Stop No

22 18 Red No Yes (with Peds) Stop No

23 4 Dilemma No No Stop No

24 13 Green Yes No Go No
13

Table 4-3: Order III description by scenario ID, signal phase, and values of independent 

factors.

(9)

Position Scenario 

ID

Signal 

Phase

Redlight 

camera

Pedestrian 

Countdown 

Signal

Adjacent 

Vehicle

Oncoming 

Left-Turn 

Traffic

1 20 Green No Yes (with Peds) No No

2 18 Red No Yes (with Peds) Stop No

3 1 Dilemma Yes Yes Stop No

4 21 Green No No Go Yes

5 3 Dilemma No Yes Stop No

6 15 Green Yes No No No

7 17 Green No Yes (no Peds) Go Yes

8 8 Dilemma No No Go No

9 11 Green Yes Yes (with Peds) No No

10 24 Green No No No No

11 14 Green Yes No Go Yes

12 6 Dilemma Yes No Go No

13 12 Green Yes Yes (no Peds) No Yes

14 10 Green Yes Yes (no Peds) Go Yes

15 4 Dilemma No No Stop No

16 13 Green Yes No Go No

17 2 Dilemma Yes No Stop No

18 23 Green No No No Yes

19 9 Red Yes Yes (with Peds) Stop No

20 19 Green No Yes (no Peds) No Yes

21 5 Dilemma Yes Yes Go No

22 16 Green Yes No No Yes

23 7 Dilemma No Yes Go No

24 22 Green No No Go No
14

Table 4-4: Order IV description by scenario ID, signal phase, and values of independent 

factors.

(9)

Position Scenario 

ID

Signal 

Phase

Redlight 

camera

Pedestrian 

Countdown 

Signal

Adjacent 

Vehicle

Oncoming 

Left-Turn 

Traffic

1 12 Green Yes Yes (no Peds) No Yes

2 9 Red Yes Yes (with Peds) Stop No

3 6 Dilemma Yes No Go No

4 24 Green No No No No

5 8 Dilemma No No Go No

6 11 Green Yes Yes (with Peds) No No

7 14 Green Yes No Go Yes

8 2 Dilemma Yes No Stop No

9 13 Green Yes No Go No

10 23 Green No No No Yes

11 18 Red No Yes (with Peds) Stop No

12 4 Dilemma No No Stop No

13 20 Green No Yes (with Peds) No No

14 22 Green No No Go No

15 7 Dilemma No Yes Go No

16 16 Green Yes No No Yes

17 5 Dilemma Yes Yes Go No

18 19 Green No Yes (no Peds) No Yes

19 10 Green Yes Yes (no Peds) Go Yes

20 21 Green No No Go Yes

21 3 Dilemma No Yes Stop No

22 15 Green Yes No No No

23 1 Dilemma Yes Yes Stop No

24 17 Green No Yes (no Peds) Go Yes

The distance at which DZs were triggered depended on the facility speed limit. For the 40 mi/h 

(64.37 km/h) case, the DZ triggered when the driver was 852.30 feet (259.78 m) from the stop 

bar, and the signal turned yellow 10 seconds later. The yellow phase lasted 4 seconds, and the 

red phase lasted 38 seconds. For the 55 mi/h (88.51 km/h) case, the DZ triggered when the 

driver was 812.20 feet (247.56 m) from the stop bar, and the signal turned yellow 5 seconds

later. The yellow phase lasted 5 seconds, and the red phase lasted 15 seconds. 

The duration of the yellow phase in both cases met the traffic signal control guideline (i.e., 

yellow change interval) established in the Traffic Engineering Handbook. (13) The period of time 

from when the DZ was triggered until the onset of the yellow phase incorporated the 

pedestrian countdown signal timing. 
15

The pedestrian countdown started at 9 seconds to the stop bar for the 40 mi/h (64.37) drive 

and 4 seconds to the stop bar for the 55 mi/h (88.51 km/h) drive.

Oncoming left-turn traffic was present for half (8) of the non-DZ intersections; there was no 

oncoming traffic at DZ intersections (see Table 4-1 for a more detailed description). There was 

also no oncoming traffic at the forced red phase intersections. For forced green phase 

intersections, left-turning vehicles crossed through the intersection before the driver entered 

the intersection. These vehicles were included to make the simulation appear more realistic to 

the driver and to mimic the possible threat of a left-turning vehicle at the DZ intersections. The 

oncoming traffic turned in the presence of the driver but did not interact with the driver in any 

way. There were three to five pedestrians crossing in each direction on the near crosswalk (see

Figure 4-1) at both of the forced red phase intersections and two of the forced green phase 

intersections; there were no pedestrians at DZ intersections. Pedestrians were included to 

make the simulation appear more realistic to the driver.

Regardless of whether a DZ was present, the designs of the red-light photo enforcement 

camera and pedestrian countdown signal were the same. The intersections with a red-light 

photo enforcement camera were appropriately signed; the signal warning sign (W3-3)(14)

mounting the photo-enforced plaque (W16-10P)(14) was displayed in advance of the 

intersection (i.e., 500 feet), and the red-light photo enforced sign (R10-19-DE) (14) was displayed 

at the intersection. The light-emitting diodes (LED) pedestrian countdown signal (14) was located 

at the intersection.
16

4.1.3 Highway Driving Simulator

The HDS consisted of a late model compact car chassis mounted inside a section of a cylindrical 

projection screen. The car was instrumented so that normal driver functions, visual scenes, and 

audio were interactive. 

Figure 4-2: Photograph. Driving simulator used for the study.

The cylindrical screen had a horizontal radius of 107 inches (271.78 cm) and a vertical height of 

95 inches (241.30 cm). It wrapped around the center (also known as the eye point) for a total of 

240 degrees. When looking at the center of the projections, the driver’s eye point was between 

0 and 8 inches (20.32 cm) to the rear from the center of the cylinder. Three BARCO SIM10 liquid

crystal on silicon digital projectors, each with a resolution of 4,096 by 2,400 pixels, provided the 

screen image. The luminance of each projector was measured three times. Across the three 

projectors, the mean luminance was 41.62 foot-lambert (fL); (142.60 candela per square meter

(cd/m2), with a range from 40.86 fL (140.00 cd/m2) to 42.26 fL (144.79 cd/m2). The combined 

image of the 3 projectors covered 200 degrees around the center of the screen. A cluster of 

personal computers with high-resolution graphics cards were used for rendering the scene 

image and controlling the real-time scenario. The system updated at a rate of 60 Hertz. The 

setup of the HDS is shown in Figure 4-2.

4.1.3.1 Post-Participation Questionnaire

Participants completed a questionnaire after their final drive. The questionnaire was 

administered through MediaLab®software on a laptop computer. On the questionnaire, 

participants answered questions regarding whether they stopped at or proceeded through the 

DZ intersections and why, and whether they noticed or were influenced by the red-light photo 

enforcement cameras, pedestrian countdown signals, and adjacent vehicles. 
17

For the purposes of the questionnaire, DZ intersections were defined as follows: “During each 

of the simulated drives, some of the traffic signals turned to yellow as you were approaching 

the intersection. Consider your behavior at these intersections (whether you stopped at or 

proceeded through the intersection) for the remaining questions.” Followup questions 

regarding red-light running behaviors in the real world were also included. The specific wording 

for each question is in Appendix A. Post-Participation Survey.

4.1.4 Participants

Originally, 24 participants for each group (A–D) were planned to be recruited in this study. 

However, considering a 25 percent dropout rate due to simulator sickness, 121 participants 

were recruited and began testing. Participants were between 18 and 72 years of age, with 

roughly equal numbers of younger (44 years or younger) and older (45 years or older) drivers in 

each group. Additionally, there were roughly equal numbers of male and female drivers in each 

group. All participants had a valid driver’s license. Based on the possession of a license, visual 

acuity was assumed to be at least 20/40 (corrected, if necessary) in at least one eye. Of 121 

participants, 19 drivers chose to discontinue due to simulator sickness. Two drivers were forced 

to discontinue due to problems with the simulator, and one driver was removed from the study 

due to erratic driving behaviors and rule breaking. The remaining 99 participants (51 males) 

completed the study. Therefore, responses of the 99 participants were used in this study.

The HDS was also equipped with a six-degree-of-freedom (tilt, roll, and yaw) motion base. The 

motion base was turned on for approximately the first month of data collection and then 

turned off to mitigate high rates of simulator sickness. Of those who completed the study, 29 

participants drove the study with the motion base turned on, and 70 participants drove the 

study with the motion base turned off. Participants were also split by age group, either younger 

(44 years or younger) or older (45 years or older). Approximately half of the participants fell 

into each age group. The mean age of the males was 47 years (range 19 to 82 years), and the 

mean age of the females was 46 years (range 18 to 80 years). 

4.1.5 Procedures

Each participant completed a practice drive to become acquainted with the simulator. The 

practice drive includes four intersections with two green and two red signals. The practice 

roadway mirrored what was used in the test drives, but no manipulations (e.g., pedestrian 

countdown signals and red-light photo enforcement cameras) were present. No dilemma zones 

were introduced in the practice drive. If participants had become familiar with the yellow phase 

timing during the practice drive, they could have made decisions (i.e., accelerate or decelerate 

their vehicles) before a traffic signal turned to the yellow phase in order to avoid dilemma 

zones. The signals in the practice drive mimicked the time and duration of the signals used in 

the test drives. Each participant was instructed to proceed through two green signals and stop 

at two red signals. If the researcher believed the participant was having trouble with controlling 

the vehicle on the driving simulator, then the researcher asked the participant to continue until 

a higher level of comfort was achieved.
18

Next, the participants completed a series of three drives. Each drive (a series of 24 

intersections) lasted approximately 16 to 22 minutes, depending on the posted facility speed 

(40 mi/h or 55 mi/h) and the number of times the driver stopped at the DZ intersections. 

Participants took a short break between drives and were asked to complete a simulator 

sickness questionnaire so that symptoms of simulator sickness could be monitored.

(15) After the 

third drive, researchers administered the post-participation questionnaire.

4.1.6 Instructions

Researchers verbally informed participants of the instructions before each drive, including 

before the practice drive. All participants were reminded of the posted speed limit and were 

asked to stay in the right lane and not change lanes. Participants were offered a $10 bonus, as 

described below, in addition to the $80 they received for participation. (16)

To advise participants of aerial speed enforcement and red-light photo enforcement in the 

scenarios, researchers read the following to the participants:

“You have been told by a friend that this road has aerial speed enforcement. 

Your friend received a ticket for going 8 miles per hour over the speed limit. If 

you receive a speeding ticket, you will be charged a fee of $1 from your overall 

bonus amount. 

There will also be red-light photo enforcement at some of the intersections. The 

red-light photo enforcement camera is triggered if your vehicle enters the 

intersection after the signal has turned to red. If you commit a red-light violation

at these intersections, then you will lose $0.50 per violation from your overall 

bonus amount.”

If the drivers were to be in a hurry, then researchers also read the following to advise them of 

penalties if they did not meet their expected completion time (18.5 minutes for the 55 mi/h 

(88.51 km/h) group and 22.5 minutes for the 40 mi/h (64.37 km/h) group).

“You are running late for a doctor’s appointment. If you finish the simulation in 

__ minutes, then you will arrive on time for the appointment. However, if you 

arrive late for the appointment, then you will be charged a late fee of $1 from 

your overall bonus amount.”

As listed above, deductions occurred if drivers were late or speeding. For the speeding 

deduction in the 40 mi/h (64.37 km/h) case, participants needed to drive 45 mi/h (72.42 km/h) 

or more for at least 30 seconds. For the speeding deduction in the 50 mi/h (88.51 km/h) case, 

participants needed to drive 60 mi/h (96.56 km/h) or more for at least 20 seconds. 

In addition, drivers received a $1 deduction if they changed lanes. Participants were not 

penalized beyond the $10 bonus they were originally offered.
19

4.2 Results

4.2.1 Influence of Motion Base

One concern was whether it was appropriate to combine data from participants who 

completed the study with the motion base turned on with those who did not. It was believed 

that this particular study would have a high simulator sickness rate because of the many stops. 

Given that the inclusion of the motion may have increased the severity and frequency of 

simulator sickness, one may hypothesize that drivers would, over time, start to proceed 

through the yellow signal phase to avoid stopping. In other words, the probability of proceeding 

through a DZ intersection would increase across the three drives.

Generalized estimating equations (GEE) with a binomial response distribution and logit link 

function were used to determine whether the probability of proceeding through a DZ 

intersection changed over time for those drivers who completed the study with the motion 

base turned on and those who completed it with the motion base turned off. The predictors in 

the model were motion, drive number, and the interaction between the two. Wald Type III 

statistics indicated that the drive number was the only significant effect with 95 percent 

confidence interval (CI); χ

2

(2) = 9.69, p = 0.0078. Both motion and the interaction of motion 

with drive number were not significant. Therefore, it was deemed appropriate to combine the 

two groups.

4.2.2 Driver Performance Measures

GEEs with a binomial response distribution and logit link function were used to determine 

whether the probability of proceeding through a DZ intersection varied regarding the different 

design factors. An exchangeable correlation structure was assumed. Due to the limited number 

of observations from 99 participants, only second-order interaction effects were considered. 

The drive number, which significantly affected the probability of a driver proceeding through a 

DZ intersection in the previous analysis, was selected as the interaction factor with other 

factors. Thus, the predictors in the model were facility speed limit (FacilitySpeed), degree of 

driving in a hurry (InAHurry), presence of a red-light photo enforcement camera (RedLightCam), 

presence of a pedestrian countdown signal (PedCountSig), behavior of the adjacent vehicle 

(AdjVehBeh), drive number (Drive), and all second-order interactions with the drive number. 

Wald Type III statistics for this analysis are shown in Table 4-5. Significant effects with 95 

percent CI, printed in boldface red, are discussed in more detail in the following sections.
20

Table 4-5: Wald Type III statistics for GEE analysis of the probability of proceeding through a 

DZ intersection regarding the different design factors.

Wald Statistics For Type 3 GEE Analysis

Source DF Chi-Square Pr > ChiSq Significant Effects with 95% CI?

FacilitySpeed 1 6.78 0.0092 Yes

InAHurry 1 36.69 <0.0001 Yes

RedLightCam 1 4.30 0.0380 Yes

PedCountSig 1 36.86 <0.0001 Yes

AdjVehBeh 1 8.28 0.0040 Yes

Drive 2 0.67 0.7136 No

Drive*FacilitySpeed 2 1.55 0.4601 No

Drive*InAHurry 2 8.94 0.0114 Yes

Drive*RedLightCam 2 10.55 0.0051 Yes

Drive*PedCountSig 2 1.24 0.5379 No

Drive*AdjVehBeh 2 1.68 0.4319 No

4.2.2.1 Between-Group Factors

There were two between-group design factors: facility speed limit (FacilitySpeed) and degree of 

driving in a hurry (InAHurry). The main effects for both were significant, and the interaction of 

the drive number with degree of driving in a hurry was also significant. 

Participants in the 40 mi/h (64.37 km/h) speed condition had a higher probability of continuing 

through a DZ intersection (M = 0.43 with a 95 percent CI of [0.31, 0.56]) than those in the 55 

mi/h (88.51 km/h) speed condition (M = 0.25 with a 95 percent CI of [0.17, 0.36]). There are at 

least two possible rationales for this. First, participants most likely knew from their real-world 

driving experience that it would take longer to come to a complete stop when traveling at 55 

mi/h (88.51 km/h). Thus, these drivers may have anticipated the need to stop and been more 

conscientious in taking notice and being cautious when the signal changed from green to 

yellow. Second, based on the developed signal timing (see section 4.1.1), participants in the 55 

mi/h (88.51 km/h) speed condition had approximately 0.9 seconds longer to come to a 

complete stop than their slower counterparts. The time to a complete stop is 3.4 seconds in the 

40 mi/h zone and 4.3 seconds in the 55 mi/h zone when the perception reaction time (PRT) is 1 

second. Although this was consistent with the physics needed to stop a car traveling at higher 

speeds, it may have allowed participants more time to come to a complete stop at the DZ 

intersections; thus, these drivers may have been more willing to stop.
21

Figure 4-3: Chart. Predicted probability of proceeding through a DZ intersection by degree of 

driving in a hurry and drive number.

As shown in Figure 4-3, participants who were not tasked to drive in a hurry were fairly 

consistent in each drive in their probability of proceeding through a DZ intersection (M = 0.11

with 95 percent CI of [0.05, 0.22] at the first drive; M = 0.11 with 95 percent CI of [0.06, 0.20] at 

the second drive; and M = 0.13 with 95 percent CI of [0.06, 0.23] at the third drive). The bars in 

Figure 4-3 represent the 95 percent CI of each case. Conversely, participants who were in a 

hurry increased their probability of continuing through a DZ intersection from the first drive (M 

= 0.42 with 95 percent CI of [0.29, 0.57]), to the second drive (M = 0.58 with 95 percent CI of 

[0.44, 0.71]), and again to the third drive (M = 0.63 with 95 percent CI of [0.49, 0.75]). This 

outcome could perhaps be due to the financial penalty described to participants by the 

researchers and incorporated into the research procedure to create pressure for the drivers to 

finish the drive in a certain amount of time. The greatest increase in the probability of 

proceeding occurred between the first and second drives (a difference of 0.16). Additionally, 94 

percent of the in-a-hurry drivers (InAHurry) received a financial penalty after the first drive 

because they were late for their doctor’s appointment. In comparison, only 68 percent of the 

participants received a financial penalty after the second drive. Between the second and third 

drives, the probability of proceeding increased by only 0.05. These results imply that the 

financial penalty described by the researchers succeeded in creating time pressure for the 

drivers, and being in a hurry significantly increased the probability of a driver proceeding 

through a DZ intersection. Even on the first drive, participants who were in a hurry were four 

times more likely to continue through the intersection than their nonpressured counterparts.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 2 3

Predicted Probability of Proceeding

Drive Number

Not in a hurry

In a hurry
22

4.2.2.2 Within-Group Factors

There were three within-group design factors: presence of a red-light photo enforcement 

camera (RedLightCam), presence of a pedestrian countdown signal (PedCountSig), and behavior 

of an adjacent vehicle (AdjVehBeh). All three main effects were significant, and the interaction 

of the drive number with the presence of an enforcement camera was also significant.

Figure 4-4: Chart. Predicted probability of proceeding through a DZ intersection by presence 

of a red-light photo enforcement camera and drive number.

As the interaction term with the presence of a red-light photo enforcement camera was 

significant, the corresponding main effect will not be discussed. The results are displayed in 

Figure 4-4 where the bars represent the 95 percent CI of each case. For those intersections 

where an enforcement camera was present, the probability of proceeding increased from the 

first drive (M = 0.27 with 95 percent CI of [0.17, 0.40]) to the second (M = 0.37 with 95 percent 

CI of [0.26, 0.48]), but then plateaued and remained constant during the third drive (M = 0.36 

with 95 percent CI of [0.26, 0.47]). In comparison, for intersections without a red-light photo 

enforcement camera, the probability of continuing through a DZ intersection increased across 

all drives (M = 0.28 with 95 percent CI of [0.18, 0.41] at the first drive; M = 0.35 with 95 percent 

CI of [0.25, 0.46] at the second drive; and M = 0.42 with 95 percent CI of [0.31, 0.54] at the third 

drive). During data collection, red-light violations were noted if a participant entered the 

intersection following the onset of the red phase. However, only three violations occurred 

among all participants, and the violations were for different people. Drivers were perhaps at 

first wary of receiving a fine for a red-light violation, but then became more attentive to the 

placement of the red-light photo enforcement cameras as they became familiar with the 

simulated scenario. 

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 2 3

Predicted Probability of Proceeding

Drive Number

No photo enforcement

Photo enforcement
23

The probability of proceeding was greater for those intersections without a pedestrian 

countdown signal (M = 0.41 with 95 percent CI of [0.30, 0.54]) than for those with the 

countdown signal (M = 0.57 with 95 percent CI of [0.18, 0.38]). 

The probability of continuing was greater when the adjacent vehicle also traveled through the 

intersection (M = 0.36 with 95 percent CI of [0.25, 0.48]) than when it stopped at the signal 

(M = 0.32 with 95 percent CI of [0.23, 0.44]).

4.2.3 Post-Participation Questionnaire

4.2.3.1 Behavior at DZ Intersections

Two questions were asked to gather information on whether participants stopped at or 

proceeded through the DZ intersections (see questions 1 and 2 in Appendix A. PostParticipation Survey for more details). 

Ninety-eight percent of the participants recalled stopping at least once at a DZ intersection. The 

reasons participants gave for stopping at the DZ intersections were classified into the following 

categories: adjacent vehicle related; experiment related (e.g., feeling of being watched); normal 

driving (e.g., rule-following behaviors); pedestrian related; red-light photo enforcement camera 

related; and signal timing related. The modal categories were pedestrian related (39 percent) 

and signal timing (31 percent). Pedestrian-related rationales included the presence of the 

pedestrian countdown signal (63 percent). Signal-timing rationales included the impending 

onset of the red phase (33 percent), the distance to the intersection at the onset of the yellow 

phase (27 percent), the length of the yellow phase (20 percent), and the onset of the yellow 

phase (20 percent).

Sixty-eight percent of the participants recalled proceeding through at least one DZ intersection. 

The reasons for continuing through DZ intersections were classified into the following 

categories: to avoid a potential collision; environmental factors (e.g., pedestrian countdown 

signal; adjacent vehicle); being in a hurry; being inattentive; confidence in crossing the 

intersection before the onset of the red phase; and distance to the intersection at the onset of 

the yellow phase. The modal categories were the distance to the intersection at the onset of 

the yellow phase (40 percent) and confidence in crossing the intersection before the onset of 

the red phase (27 percent). Only six percent of the participants cited the pedestrian countdown 

signal or the adjacent vehicle in their rationales. In addition, approximately 10 percent of the 

participants provided answers indicating that they may have misunderstood the question.

4.2.3.2 Red-Light Photo Enforcement Camera Influence

Question 3 was asked to gather information on whether participants noticed the red-light 

photo enforcement camera and, if so, whether the presence of the enforcement camera 

influenced their behavior (see Appendix A. Post-Participation Survey).
24

Approximately 75 percent of the drivers claimed to have run a red light in the real world at least 

once. Of these individuals, the most common reason for doing so was because they could not 

stop in time. 

Fifty-five percent of the participants noticed the red-light photo enforcement camera present 

at some of the intersections. The following results reflect responses only from these drivers. 

Fifty-four percent of the participants believed the presence of the enforcement camera 

influenced their behavior at the DZ intersections. Additionally, 94 percent of these drivers 

thought that their behaviors in response to the enforcement camera mimicked what they 

would have done in the real world. Participants were asked to rate, on a scale from 1 (not at all 

influenced) to 10 (extremely influenced), how much the red-light photo enforcement camera 

influenced their decision at the DZ intersections. The mode was 10, and the median rating was 

5.5.

4.2.3.3 Pedestrian Countdown Signal Influence

Question 4 was asked to gather information on whether participants noticed the pedestrian 

countdown signal and, if so, whether the presence of the pedestrian countdown signal 

influenced their behavior (see Appendix A. Post-Participation Survey).

Ninety-two percent of the participants noticed the pedestrian countdown signal at some of the 

intersections. The following results reflect responses only from these drivers.

Ninety-three percent of the participants believed the presence of the pedestrian countdown 

signal influenced their behavior at the DZ intersections. Participants used the remaining time of 

the pedestrian countdown signal so that they could have a clear decision at an intersection. 

Additionally, 86 percent of these drivers thought their behaviors in response to the pedestrian 

countdown signal mimicked what they would have done in the real world. Participants were 

asked to rate, on a scale from 1 (not at all influenced) to 10 (extremely influenced), how much

the pedestrian countdown signal influenced their decision at the DZ intersections. The mode 

was 10, and the median rating was 8.0.

4.2.3.4 Adjacent Vehicle Influence

Question 5 was asked to gather information on whether participants noticed the adjacent 

vehicle and, if so, whether the presence and/or behavior of the adjacent vehicle influenced 

their behavior (see Appendix A. Post-Participation Survey). 

All participants noticed the adjacent vehicle traveling in the left lane. Only 13 percent of the 

drivers believed the presence of the adjacent vehicle influenced their behavior at the DZ 

intersections. Similarly, only 11 percent of the participants believed the behavior of the 

adjacent vehicle influenced their behavior at the DZ intersections. Eighty-four percent of the 

drivers thought their behaviors in response to the adjacent vehicle mimicked what they would 

have done in the real world. 
25

Participants were asked to rate, on a scale from 1 (not at all influenced) to 10 (extremely 

influenced), how much the adjacent vehicle influenced their decision at the DZ intersections. 

The mode was 1, and the median rating was 2.0. However, the results conflicted with the 

statistical analysis, shown in Table 4-5 (i.e., behavior of an adjacent vehicle (AdjVehBeh) was a 

significant element to the drivers’ responses at the DZ intersection). 

4.2.3.5 Real-World Experience with Red-Light Running

Questions 6 to 10 were asked to gather information about participants’ self-reported red-light 

running in actual driving. Respondents were asked to consider only their past experiences in the 

real world (see Appendix A. Post-Participation Survey).

Approximately 66 percent of participants defined running a red light as entering an intersection 

on red, while the balance defined running a red light as entering an intersection on yellow and 

the light turning to red while the car was still in the intersection. Table 4-6 and Table 4-7 show 

the distribution of how often the participants recalled other drivers and themselves running red 

lights, respectively.

Table 4-6: Distribution of how often participants recalled other drivers running red lights in 

the real world (based on their respective definition of red-light running).

Response Percentage

Every day 25

A few times a week 39

A few times a month 22

Less than once a 

month

13

Table 4-7: Distribution of how often participants recalled themselves running red lights in the 

real world (based on their respective definition of red-light running).

Response Percentage

Yes, once or twice 57

Yes, more than twice 18

No 24

Those participants who reported running a red light in the real world were asked to identify 

which factors affected their decision to do so. Multiple selections were allowed. Figure 4-5

displays what percentage of these drivers selected each factor.
26

Figure 4-5: Chart. Percentage of participants who selected each factor that affected their 

decisions to run a red light in the real world.

82.67

46.67

5.33 2.67

48.00

29.33

52.00 50.67

34.67

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

Could not

stop in

time

Afraid of

rear

collision

Side car

ran the

light

Front car

ran the

light

In a hurry No other

cars

around

Not

paying

close

attention

Unfamiliar

with area

Distracted

Percentage of Participants
27

5 Analysis Results

5.1 ABMS Scenario

5.1.1 DZ Model

The proposed driver behavior model was implemented using ABMS software. The simulation 

scenario was a segment of an urban arterial with three lanes in each direction containing two 

signalized intersections. 

Figure 5-1: Image. Screenshot of simulation. 

In the simulation (Figure 5-1), the nearest leading vehicle in the adjacent lane was considered 

the adjacent vehicle. The simulation time horizon was 30,000 hours and the number of 

replications was 30. Initial speed of vehicles was assumed to be uniformly distributed between 

23.3 mi/h and 30 mi/h. Moreover, the coming flow rate was 1,200 vehicles/hour and 

perception-reaction time (δ) was 0.7 seconds. The number of sampled vehicles is 1,000. The 

free flow speed of each group was given by drivers’ data collected by the HDS. Free flow speed 

of group A, group B, group C, and group D was Normal (38.89, 3.34) mi/h, Normal (42.38, 4.93) 

mi/h, Normal (52.67, 3.12) mi/h, and Normal (57.30, 3.34) mi/h, respectively. Parameters in the 

parenthesis represent mean and variance of the Normal distribution. Based on collected data 

from the HDS, decisionmaking behaviors of the drivers in the four groups were developed via 

the E-BDI framework (see section 5.2 for more details). The constructed simulation models

were executed under the two different facility speed limit cases (40 mi/h and 55 mi/h), as

mentioned in section 4.1.1.

5.1.2 E-BDI Framework

The E-BDI framework was used as an underlying model in ABMS to mimic participants’ 

decisionmaking behaviors shown in the DZ experiments conducted with the HDS. Because E-BDI 

generates a multistage plan via probabilistic inference, it is able to represent the uncertain 

perception and reasoning processes of humans.

(2)

In the E-BDI framework, once an agent perceives the road condition (e.g., traffic), the 

perceptual processor in the Belief module creates Beliefs via the Bayesian Belief Network 

(BBN). The BBN uses conditional probabilities between variables to infer states of attributes 

(e.g., travel time) from the observed road conditions (e.g., free flow speed, traffic volume, and 

road length). Thus, each agent can have its own Beliefs about the attributes based on the BBN 

trained by its own experience. (2)
28

Then, a real-time planner creates a multistage plan from the Beliefs. In this process, Extended 

Decision Field Theory (EDFT) is used to select one option from multiple alternatives regarding 

interdependencies between alternatives.

(17) (18) It calculates the preference values of all 

alternatives based on perception and attention of a human on each attribute of each option

(see section 0). Once the preference values converge, EDFT selects one option that has the 

highest preference value. By running EDFT multiple times with BBN, choice probabilities for all 

of the alternatives can be computed. More details on this work can be found in Lee, Son, and 

Jin (2010).

5.2 ABMS Model Calibration and Validation

5.2.1 Calibration of BBN

In the E-BDI framework, a driver’s decisionmaking behavior in the DZ was represented by BBN 

with EDFT. To be more specific, the BBN provides the states of the attributes of each option 

from the environmental factors, and the EDFT computes the preferences on each option 

regarding the psychological aspect of driver deliberation. As mentioned in section 4.1.1, there 

were four groups classified by facility speed and degree of driving in a hurry. Each group had 

three environmental factors (i.e., RedLightCam, PedCountSig, and AdjVehBeh). In addition to 

these three factors, two more factors (distance to stop line of a vehicle (Distance) and 

approaching speed of a vehicle at the onset of the yellow phase (AppSpeed)), as included in the 

existing ITE DZ model, (1) were considered to represent the status of an individual vehicle. To 

identify the impacts of the three environmental factors (i.e., external information) and the 

status of the individual vehicle (i.e., internal information) on the driver’s decision in the DZ, 

external information and internal information were considered as attributes in the E-BDI 

framework.

The challenge of calibration is how to measure the correlations between the five observed 

factors and two attributes (i.e., two latent variables: internal information and external 

information). Although the status of the attributes is not observed by the HDS, the status can 

be inferred from the five observed factors and the drivers’ decisions by an SEM approach. 

Structural equation modeling is a statistical technique for testing and estimating causal 

relations using a combination of statistical data and causal assumptions that has been widely 

used to find the relationships between observed variables and latent variables. (19) Figure 5-2

shows the hypothetical model for SEM analysis.

(9)
29

© Elsevier B.V.

Figure 5-2: Chart. Path model in SEM analysis.

(9)

Table 5-1 shows the standardized regression weights of each group. (9)

Table 5-1: Standardized regression weights of driver groups. (9)

Causal Relation Group A Group B Group C Group D

AppSpeed -> Internal information –.775 –.629 –.523 –.816

Distance -> Internal information .935 .923 1.285 .919

PedCountSig -> External information –.181 –.130 - –.194

RedLightCam -> External information .091 –.034 - –.020

AdjVehBeh -> External information .055 .036 - .018

Decision <- Internal information .245 .261 .880 .270

Decision <- External information 1.043 1.361 - 1.032

To evaluate the validity of the developed models, a χ2goodness of fit test was conducted (H0: 

the data are consistent with the developed model; Ha: the data are not consistent with the 

developed model). The χ

2

/df value of the models was 1.846/7 (group A), 1.206/7 (group B), 

2.274/7 (group C), and 3.926/7 (group D). In general, if χ

2

/df is less than 3, the model would be 

considered a desirable model for the given dataset.

(19) Thus, the path model shown in 

Figure 5-2 was used as a fitted model to explain the collected data by HDS in this study (the 

model can be different based on a collected dataset). Regarding the standardized regression 

weight of each group, drivers in group A, group B, and group D were more sensitive to external 

information than internal information, i.e., Decision <- Internal information. 
30

This sensitivity implies that the existing ITE DZ model, which mainly considers AppSpeed and 

Distance, would not be sufficient to explain the driver’s decision when the driver also had 

external information. The gap in the standardized regression weights between internal 

information and external information in affecting a decision also shows that group B (i.e., 

|0.261–1.361| = 0.900) and group D (i.e., |0.270–1.032| = 0.762) cared more about external 

information than group A (i.e., |0.245–1.043| = 0.798) and that for group C, there was no 

impact of external information. In other words, external information was considered to a 

significant extent by drivers in the in-a-hurry situation. 

From the SEM approach, the status of each attribute was estimated. Figure 5-3 shows the 

developed BBN.

(9) In this process, the values of each attribute were discretized and normalized 

to use the same scale in the EDFT algorithm for each option. In fact, if there was no significant 

impact on the inference accuracy of the BBN, discretization of a continuous factor reduced the 

space complexity of the BBN so that inference process using the BBN could be improved.

© Elsevier B.V.

Figure 5-3: Chart. BBN for E-BDI framework.

(9)

The advantage of BBN is its ability to infer the status of attributes even though only partial 

observations of the parent variables (i.e., AppSpeed, Distance, RedLightCam, PedCountSig, and 

AdjVehBeh) were available. Additionally, because it is a probabilistic model using conditional 

probabilities between variables, BBN could handle the driver’s uncertain perception process.

5.2.2 Calibration of EDFT

The calibration of EDFT is the process to find the parameters of EDFT to mimic real drivers’ 

decisionmaking behaviors in the DZ. 

Figure 5-4 shows the EDFT used in this study.

(9)
31

Figure 5-4: Equation. EDFT used in the DZ.

(9)

The first term on the right-hand side includes a stability matrix (S) to consider the effect of the 

preference at the previous state (the memory effect) and preference values (P) of two 

alternatives at time t. The second term on the right-hand side includes a contrast matrix (C) 

regarding the correlation between alternatives, a value matrix (M(t+h)) to represent the 

subjective perception of a human on each attribute of each option, and a weight vector (W(t)) 

to assign the weights of attention on each attribute. (9) (17) (18)

By fixing the values of the stability matrix S and contrast matrix C, the calibration process could 

be simplified as a searching process for the appropriate weight vector (W(t)) of each driver 

group under the given value matrix M(t). In this study, by comparing the decisions of real 

drivers with the inferred decisions given by the E-BDI framework, the weight vector W(t) with 

the highest prediction accuracy was found. Table 5-2

(9) reveals the selected weight vectors.(9)

Table 5-2: Weight vector of driver groups.

Weight Vector Group A Group B Group C Group D

W(t) = (

wint (t)

wext (t)

) (

0.16

0.84) (

0.11

0.89) (

1

0

) (

0.08

0.92)

5.3 Modeling Experiments

To analyze the simulation results, a Speed-Distance (SD) diagram was used. The SD diagram 

shows drivers’ decisions, together with the vehicles’ approaching speed and distance to the 

stop line, at the onset of the yellow phase. In an SD diagram, there are two curves; one is called 

the stopping curve and the other is called the crossing curve. (9) The stopping curve represents 

the limited stopping distance under different vehicle speeds with respect to comfortable 

deceleration (i.e., –3.72 m/sec2in this research, as given by the Traffic Engineering 

Handbook). (13) Similarly, the crossing curve represents the limited crossing distance under 

different vehicle speeds within the length of the yellow phase. 

By using these two curves, the space in the SD diagram can be separated into four zones: (1)

cross zone-space beyond both curves, (2) stop zone-space under both curves, (3) option zonespace under stopping curve and above crossing curve, and (4) DZ-space under crossing curve 

and above stopping curve. A driver is able to clear the intersection with the current 

approaching speed before the traffic signal turns red in the cross zone and to stop comfortably 

at the stop line in the stop zone. Otherwise, a driver must choose either to go or to stop when 

the driver is in the DZ or the option zone.
32

5.3.1 Low-Facility Speed Limit

In this scenario, the simulation model consisted of 50 percent group A vehicles and 50 percent

group B vehicles.

Figure 5-5

(9)and Figure 5-6(9)show the experimental results under different configurations of 

RedLightCam and PedCountSig (i.e., presence or not). On the one hand, among the vehicles in 

Figure 5-5 (no RedLightCam and no PedCountSig), 36.31 percent cleared the intersection 

successfully (red stars), 60.71 percent stopped (blue circles), and 2.98 percent chose to cross 

but had to run a red light. On the other hand, among all vehicles in Figure 5-6 (RedLightCam

and PedCountSig present), 36.37 percent cleared the intersection successfully (red stars), 61.22 

percent stopped (blue circles), and 2.41 percent chose to cross but had to run a red light (black 

triangles). According to the definition of the option zone, there were no vehicles running a red 

light in the option zone because drivers could either stop their vehicles or go through an 

intersection before the traffic signal changed to a red light. However, because of traffic on the 

roadway, drivers could not suddenly change their vehicle speed. In other words, the actual 

maximum acceleration rate and deceleration rate were different from the theoretical values. 

Thus, vehicles that ran red lights were detected in the simulation model. In addition, comparing 

the proportion of red-light running vehicles in the two figures, when RedLightCam and 

PedCountSig were present, they were able to reduce the number of red-light running vehicles

(i.e., from 2.98 percent to 2.41 percent).

© Elsevier B.V.

Figure 5-5: Chart. SD diagram of Group A (RedLightCam=no and PedCountSig=no). (9)
33

© Elsevier B.V.

Figure 5-6: Chart. SD diagram of Group A (RedLightCam=yes and PedCountSig=yes). (9)

When the red-light photo enforcement camera and pedestrian countdown signal do not exist at 

a signalized intersection (no RedLightCam and no PedCountSig), among all vehicles in group B, 

36.60 percent cleared the intersection successfully (red stars), 60.85 percent stopped (blue 

circles), and 2.55 percent chose to cross but had to run a red light (black triangles) to do so. 

On the other hand, when the RedLightCam and PedCountSig present, 39.38 percent cleared the 

intersection successfully (red stars), 58.94 percent stopped (blue circles), and 1.68 percent

chose to cross but had to run a red light (black triangles). As found for group A, the presence of 

RedLightCam and PedCountSig reduced the number of vehicles running red lights. Significantly, 

group B had a higher reduction in the amount of red-light running vehicles (0.87 percent) than 

group A (0.57 percent) because drivers who were driving in the in-a-hurry situation cared more 

about the external information than other drivers who were driving in a normal situation.

Table 5-3: Summary of experiments (group A: 90 percent; group B: 10 percent).

Group Presence of PedCountSig 

and RedLightCam Crossed Stopped Red-light running

A Yes 36.49 60.85 2.66

A No 31.51 65.35 3.13

B Yes 34.91 63.20 1.89

B No 33.48 63.87 2.65
34

Table 5-4: Summary of experiments (group A: 10 percent; group B: 90 percent).

Group Presence of PedCountSig

and RedLightCam Crossed Stopped Red-light running

A Yes 40.28 57.64 2.08

A No 33.91 63.29 2.80

B Yes 39.35 59.35 1.29

B No 34.14 62.84 2.43

Table 5-3 and Table 5-4 show the average numbers of crossed, stopped, and red-light running

vehicles collected by 30 replications of each scenario. As previously mentioned, the presence of 

RedLightCam and PedCountSig reduced the number of red-light violations for group A and 

group B. In addition, the impact of RedLightCam and PedCountSig on drivers’ decisions 

increased when the roadway had a greater number of group B vehicles, as shown in the tables 

on the reduction of red-light violations. Table 5-3 had a 0.47 percent reduction for group A and 

a 0.76 percent reduction for group B, and Table 5-4 had a 0.72 percent reduction for group A 

and 1.14 percent for group B because the drivers in group B considered the external 

information more significantly than those in group A. Moreover, group A had more red-light 

running vehicles than group B. This result meant that the approaching speed of group A was too 

slow to cross the intersection within the yellow phase (group A has Normal (38.89, 3.34) mi/h

speed distribution and group B has Normal (42.38, 4.93) mi/h speed distribution). 

5.3.2 High-Facility Speed Limit

Unlike group A and group B, drivers’ decisions in group C were only related to the internal 

information mentioned in section 5.2. 

Among all vehicles in group C, 56.24 percent cleared the intersection successfully (red stars), 

42.26 percent stopped (blue circles), and 1.50 percent chose to cross but had to run the red

light (black triangles). Comparing the distribution of decisions with group A, the number of redlight running vehicles in group C was smaller than the number of red-light running vehicles in 

group A. Noting that group C drivers had a 55 mile-per-hour speed limit, this smaller number of 

violations meant that drivers could make clear decisions under the high-facility speed limit 

(FacilitySpeed) under the experimental settings.
35

© Elsevier B.V.

Figure 5-7: Chart. SD diagram of group D (RedLightCam=no and PedCountSig=no). (9)

© Elsevier B.V.

Figure 5-8: Chart. SD diagram of group D (RedLightCam=yes and PedCountSig=yes). (9)

Group D, however, had different decisionmaking patterns from group C. Figure 5-7

(9) and

Figure 5-8

(9) show the experimental results of group D. Among the vehicles in Figure 5-7, 57.72

percent cleared the intersection successfully (red stars), 40.68 percent stopped (blue circles), 

and 1.60 percent chose to cross but had to run the red light (black triangles). 
36

Comparing the distribution of decisions in group D with group C, an urgent situation (i.e., 

driving in a hurry) made drivers have uncertain decisions. In other words, it increased the 

potential risk of a car crash at an intersection. If RedLightCam and PedCountSig were present at 

the intersection, the uncertainty was significantly mitigated. In Figure 5-8, 55.25 percent

cleared the intersection successfully (red stars), 43.29 percent stopped (blue circles), and 1.46

percent chose to cross but had to run the red light (black triangles).

Similar to the low-facility speed limit case, experiments under different configurations of group 

C and group D were conducted. Table 5-5 and Table 5-6 show the average numbers of vehicles 

that crossed, stopped, red-light-running vehicles collected by 30 replications of each scenario. 

As indicated in Figure 5-7 and Figure 5-8, the presence of RedLightCam and PedCountSig

reduced the number of red-light running vehicles. The number of red-light running vehicles

decreased as the percentage of group D increased from 90 percent to 10 percent. The 

reduction in the amount of red-light running vehicles of group D was 0.06 percent in Table 5-5

and 0.43 percent in Table 5-6. Group C had a 0.01 percent reduction in Table 5-5 and 0.09 

percent reduction in Table 5-6.

In fact, because the decision model of group C did not include external information as an 

attribute, the number of light violations of group C should not be affected by the presence of 

RedLightCam and PedCountSig. However, group C shared a roadway with group D, which was 

influenced by the external information so that group C was indirectly affected by the external 

information via physical interactions (i.e., actual movements of vehicles) with vehicles in group 

D. Therefore, in group C, there were small differences according to the presence of 

RedLightCam and PedCountSig.
37

Table 5-5: Summary of experiments (group C: 90 percent; group D: 10 percent).

Group RedLightCam and 

PedCountSig

Crossed Stopped Red-light 

running

C Yes 57.27 41.88 0.85

C No 56.80 42.34 0.86

D Yes 57.12 41.08 1.80

D No 54.78 43.36 1.86

Table 5-6: Summary of experiments (group C: 10 percent; group D: 90 percent).

Group RedLightCam and 

PedCountSig

Crossed Stopped Red-light 

running

C Yes 49.25 50.00 0.75

C No 52.93 46.23 0.84

D Yes 58.92 40.06 1.02

D No 56.34 42.21 1.45

5.4 Discussions

The E-BDI-based DZ model was proposed to predict drivers’ decisions at an intersection. The 

proposed model can be used to assist in intersection design to reduce the potential risk of 

crashes as a result of drivers’ responses. In addition to the two factors considered in the ITE DZ 

model (i.e., AppSpeed and Distance), various external factors in the roadway environment (i.e., 

RedLightCam, PedCountSig, and AdjVehBeh) were considered. The first two factors were 

defined as internal information, and the other three factors were defined as external 

information. The internal and external information were used as attributes in the E-BDI-based 

DZ model.

From the drivers’ responses collected by the HDS, SEM analyzed the impact of unobserved 

attributes (i.e., internal information and external information) on drivers’ decisions in the DZ. 

According to the standardized regression weights given by SEM, most driver groups, except 

group C, used both external and internal information for their decisionmaking. 

The SEM analysis results were utilized to calibrate BBN and EDFT in the E-BDI-based model to 

understand the impact of internal and external information on drivers’ decisionmaking 

behaviors in the DZ. 

According to the calibration results, when drivers were in a hurry situation (i.e., group B and 

group D), drivers’ decisionmaking behaviors were significantly affected by the external 

information.
38

Agent-based modeling and simulation with the calibrated E-BDI-based DZ model showed the 

impact of external information via SD diagrams. It was executed with multiple vehicles to 

consider physical interactions between vehicles. The experimental results revealed that drivers 

tended to have a higher number of red-light running vehicles when a pedestrian countdown 

signal and a red-light photo enforcement camera were not installed at an intersection. The 

presence of a pedestrian countdown signal and red-light photo enforcement camera were able 

to reduce the number of red-light running vehicles significantly, particularly when drivers were 

in a situation that called for them to be in a hurry. The findings corresponded to the results 

from the E-BDI-based DZ model calibration. This is a good proof of concept for the potential 

development of a model to predict driver decisions in the DZ via ABMS with the E-BDI-based DZ 

model.
39

6 Concluding Remarks

This report provided details about the work on developing a novel DZ model based on ABMS. In 

order to develop a realistic driver’s behavior model regarding the uncertainty of a driver’s 

perception and decision, the E-BDI framework was adopted. In the E-BDI framework, internal 

information (i.e., vehicle’s approaching speed and distance to stop line at the onset of the 

yellow phase) and external information (i.e., presence of a red-light photo enforcement

camera, presence of a pedestrian countdown signal, and behavior of an adjacent vehicle) were

considered as major factors on the stopping and proceeding decisions of a driver. In addition, 

the impact of factors on drivers’ decisionmaking behaviors in the DZ was analyzed under four 

roadway conditions classified by facility speed limit of the roadway and degree of driving in a 

hurry. The highway driving simulator was used to collect real drivers’ responses and to calibrate

the ABMS model with E-BDI framework. To demonstrate and validate our proposed approach, 

the drivers’ behaviors under two cases were compared: (1) drivers only knew the approaching 

speed and distance to the stop line of a vehicle (i.e., internal information), and (2) drivers knew 

the internal information as well as the external information. The experiments revealed that 

knowing the external information could predict real drivers’ behaviors accurately and reduce 

the number of red-light violations, which could cause potential car crashes at an intersection.

41

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43

Appendix A. Post-Participation Survey

Congratulations! You have just completed your series of three drives.

Next you will complete a short survey about your experiences in the simulator and how those 

experiences compare to similar situations in the real world. The survey will take about 5 

minutes to complete. Please answer as honestly and thoroughly as possible.

Some of the questions will be multiple choice. For these questions, you can click on the answer 

choice number or use the keypad on the keyboard. Other questions will be fill in the blank. For 

those questions, please type your response and hit “ENTER” on the keyboard.

At this time, please let the experimenter know if you have any questions. Once you are ready, 

please click “CONTINUE” at the bottom of the screen.

During each of the simulated drives, some of the traffic signals turned to yellow as you were 

approaching the intersection. Consider your behavior at these intersections (whether you stopped at or 

proceeded through the intersection) for the remaining questions.

1. Did you ever stop at one of these intersections?

A. YES

B. NO

If “YES” ...

What factors, if any, influenced your decision to stop at the intersection? (Fill in the blank)

2. Did you ever proceed through one of these intersections?

A. YES

B. NO

If “YES” ...

What factors, if any, influenced your decision to proceed through the intersection? (Fill in the blank)
44

3. Did you notice the red-light camera present at some of the intersections?

A. YES

B. NO

If “YES” ...

Did the presence of the red-light camera influence your decision to proceed through or stop at the 

intersection?

A. YES

B. NO

If “YES” ...

How did the red-light camera influence your decision at the intersection? (Fill in the blank)

If “NO” ...

Why did the red-light camera not influence your decision at the intersection? (Fill in the blank)

Was your behavior in response to the red-light camera similar to what you would have done in the real 

world?

A. YES

B. NO

If “NO” ...

What would you have done differently in the real world in response to the red-light camera? (Fill 

in the blank)

On a scale from 1 to 10, how much did the red-light camera influence your decision to proceed through 

or stop at the intersection?

1 2 3 4 5 6 7 8 9 10

Not at All Extremely 

Influenced
45

4. Did you notice the pedestrian countdown signal at some of the intersections?

A. YES

B. NO

If “YES” ...

Did the presence of the pedestrian countdown signal influence your decision to proceed through or stop 

at the intersection?

A. YES

B. NO

If “YES” ...

How did the pedestrian countdown signal influence your decision at the intersection? (Fill in the 

blank)

If “NO” ...

Why did the pedestrian countdown signal not influence your decision at the intersection? (Fill in 

the blank)

Was your behavior in response to the pedestrian countdown signal similar to what you would have done 

in the real world?

A. YES

B. NO

If “NO” ...

What would you have done differently in the real world in response to the pedestrian 

countdown signal? (Fill in the blank)

On a scale from 1 to 10, how much did the pedestrian countdown signal influence your decision to 

proceed through or stop at the intersection?

1 2 3 4 5 6 7 8 9 10

Not at All Extremely 

Influenced

5. Did you notice the vehicle that occasionally traveled next to you in left lane?

A. YES

B. NO
46

If “YES” ...

Did the presence of the adjacent vehicle influence your decision to proceed through or stop at the 

intersection?

A. YES

B. NO

If “YES” ...

How did the presence of the adjacent vehicle influence your decision at the intersection? (Fill in 

the blank)

If “NO” ...

Why did the presence of the adjacent vehicle not influence your decision at the intersection? 

(Fill in the blank)

Sometimes the adjacent vehicle would travel through the intersection and other times it would stop at 

the intersection.

Did the behavior of the adjacent vehicle influence your decision to proceed through or stop at the 

intersection?

A. YES

B. NO

If “YES” ...

How did the behavior of the adjacent vehicle influence your decision at the intersection? (Fill in 

the blank)

If “NO” ...

Why did the behavior of the adjacent vehicle not influence your decision at the intersection? 

(Fill in the blank)

Was your behavior in response to the adjacent vehicle similar to what you would have done in the real 

world?

A. YES

B. NO

If “NO” ...

What would you have done differently in the real world in response to the adjacent vehicle? (Fill 

in the blank)
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On a scale from 1 to 10, how much did the adjacent vehicle influence your decision at the intersection?

1 2 3 4 5 6 7 8 9 10

Not at All Extremely 

Influenced

6. For the following questions, please consider only your past experiences in the real world. How do 

you define running a red light?

A. Entering an intersection on yellow, but the light turns to red while the car is still in the 

intersection.

B. Entering an intersection on red.

C. Other:

7. How often do you see other drivers run red lights, based on your definition?

A. Every day.

B. A few times a week.

C. A few times a month.

D. Less than once a month.

8. Have you ever run a red light, based on your definition?

A. Yes, once or twice.

B. Yes, more than twice.

C. No.

9. In the past, what are some factors that have affected your decision to run a red light? Select all that 

apply.

A. Could not stop in time.

B. Afraid car behind me would hit me.

C. Car to the side of me ran the light first.

D. Car in front of me ran the light first.

E. In a hurry.

F. No other cars around the intersection.
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G. Not paying close enough attention.

H. Unfamiliar with area and/or did not see the light.

I. Distracted by someone and/or something in my car.

J. Other:

10. Do you have any other comments?