Cole D Fitzpatrick

Spatial and temporal analysis of driver gap acceptance behavior at modern roundabouts

Despite an increasing acceptance of modern roundabouts in the United States, unfamiliarity with this type of intersection is still widespread. This unfamiliarity results in drivers making unpredictable decisions about gap acceptance, thus increasing the difficulty of design decisions. The relationship between the spatial and temporal critical gaps accepted by drivers in modern roundabouts is explored with gap acceptance data from more than 1,500 vehicle interactions at the roundabout on the University of Massachusetts, Amherst, campus. The critical gap was determined to be 42 ft spatially and 2.2 s temporally, which correlated directly with the average speed of the circulating flow. A longer critical gap time was observed for heavy vehicles in the traffic stream. Even though the unidirectional flow of the circulating traffic creates a potentially unpredictable environment for the driver, careful and precise analysis to obtain an accurate and reliable value of the critical gap will allow for improved roundabout design.

Large-Scale Observational Study of Drivers’ Cell Phone Use

This report details the 2012 observational study used to determine drivers’ cell phone use in Massachusetts; the study was completed as a component of the annual seat belt observation study by the University of Massachusetts Traffic Safety Research Program. This study identified the magnitude of risky driving behavior throughout Massachusetts. The location, the time of day, and the direction of travel for each observation were determined by random selection with consideration given to the regions fatality rate and length of roadway. Throughout the state, the drivers’ cell phone use at any given daylight hour was determined; the timing allowed for comparisons between different populations. The apparent cell phone use of 17,677 drivers was observed at 145 locations, with a finding of an average cell phone use of 7.0%, a handheld use of 5.6%, and a text messaging use of 1.4%. Females were observed having handheld conversations at a greater rate than males, but there was little difference in text messaging use. Teens were observed text messaging more often than adults and elders, while the handheld conversation rate was similar for teens and adults. Drivers observed wearing seat belts had a lower cell phone use than those who were not wearing seat belts, for text messaging and handheld conversations. Notable variations in cell phone use were identified across various driver demographics, road types, and times of observation and furthered the understanding of drivers’ cell phone use and providing an opportunity for targeted countermeasures.

The influence of clear zone size and roadside vegetation on driver behavior

INTRODUCTION Roadside vegetation provides numerous environmental and psychological benefits to drivers. Previous studies have shown that natural landscapes can effectively lower crash rates and cause less frustration and stress to the driver. However, run-off-the-road crashes resulting in a collision with a tree are twice as likely to result in a fatality, reinforcing the need to examine the placement of vegetation within the clear zone. METHOD This study explores the relationship between the size of the clear zone and the presence of roadside vegetation on vehicle speed and lateral position. A static evaluation, distributed electronically to 100 licensed drivers, was utilized to gather speed selections for both real and virtual roads containing four combinations of clear zone sizes and roadside vegetation densities. A case study was included in the static evaluation to investigate the presence of utility poles near the edge of the road on speed selection. Validation of the static evaluation was performed by a field data collection on the same roadways shown to participants in the evaluation. RESULTS The speeds observed in the field for roadways with medium clear zone/dense vegetation or large clear zone/spare vegetation correlated with the speeds chosen by static evaluation participants. Further field data were obtained on vehicle speeds and lateral positions for additional roads demonstrating the same clear zone size/vegetation density combinations. PRACTICAL APPLICATION This study successfully demonstrates the relationship between clear zone design and driver behavior, which could improve clear zone design practices and thus roadway safety.

The use of a driving simulator to determine how time pressures impact driver aggressiveness

Speeding greatly attributes to traffic safety with approximately a third of fatal crashes in the United States being speeding-related. Previous research has identified being late as a primary cause of speeding. In this driving simulator study, a virtual drive was constructed to evaluate how time pressures, or hurried driving, affected driver speed choice and driver behavior. In particular, acceleration profiles, gap acceptance, willingness to pass, and dilemma zone behavior were used, in addition to speed, as measures to evaluate whether being late increased risky and aggressive driving behaviors. Thirty-six drivers were recruited with an equal male/female split and a broad distribution of ages. Financial incentives and completion time goals calibrated from a control group were used to generate a Hurried and Very Hurried experimental group. As compared to the control group, Very Hurried drivers selected higher speeds, accelerated faster after red lights, accepted smaller gaps on left turns, were more likely to pass a slow vehicle, and were more likely to run a yellow light in a dilemma zone situation. These trends were statistically significant and were also evident with the Hurried group but a larger sample would be needed to show statistical significance. The findings from this study provide evidence that hurried drivers select higher speeds and exhibit riskier driving behaviors. These conclusive results have possible implications in areas such as transportation funding and commercial motor vehicle safety.

Evaluation of Downstream Merge Behaviors Resulting from Driver Lane Choice: A Driving Simulator Study

With the ever-increasing demand to add roadway capacity in a safe and efficient manner, the application of auxiliary through lanes (ATLs) at intersections has increased in recent years. Despite the potential capacity-related benefits, ATLs also introduce the potential for unique driver operation tactics, leading to challenging merge scenarios downstream of signalized intersections. Furthermore, the benefits of increasing capacity are only realized when drivers are making decisions that balance the utilization of the ATL and the adjacent continuous through lane. Moreover, balancing lane utilization upstream of an ATL signalized intersection may introduce an improvement in safety and operations in merging conflicts downstream. Previous research investigated the effectiveness of ATLs through microsimulation and field studies. This research employed two full-immersion driving simulation studies. The initial experiment was conducted using simulation technology to evaluate aspects of driver behavior associated with lane utilization at ATLs. Lane utilization of the ATL significantly increased when the driver was informed of the fundamental design concept, ultimately improving capacity. The second experiment was based upon the results of the initial experiment, coupled with ongoing research evaluating alternative merge signage. Specifically, the second experiment aimed to evaluate downstream merge signage that could mitigate some of the behaviors resulting from the less than optimal lane utilization for ATLs. With an emphasis on improving intersection performance, the results from this paper suggest that the implementation of alternative merging signage may lead to improved merging behavior.

Investigation of Time and Speed Perception using a Driving Simulator

Thirty-four drivers participated in a driving simulator experiment which investigated time and speed perception as it related to cognitive workload resulting from secondary tasks. Each participant drove the virtual drive twice, once with either an audio or a map task and again with no distractions as a control. Participants knew from a practice drive that they would be asked to estimate their speed and time duration of driving, thus this study used the prospective paradigm. Based on previous literature it was expected that there would be an underestimation of time and an overestimation of speed. The reverse occurred, participants overestimated time and underestimate their speed. This suggests that drivers may have found the drive unstimulating, despite the secondary tasks, and that the rural environmental may have impacted speed perception. In addition, a large group of participants, nine out of 34, crashed the virtual vehicle at a horizontal curve that was not problematic in previous simulator studies. When investigating these crashes further, it was found that drivers who crashed in the second drive had significantly worse time perception in the first drive as compared to drivers who did not crash in the second drive. This finding suggests that current time perception may be a predictor of future speed selection.