Tapan K Datta

RED LIGHT VIOLATIONS AND CRASHES AT URBAN INTERSECTIONS

High approach speeds coupled with aggressive driving often lead to the running of red lights at intersections. When motorists see a yellow light as they approach an intersection, they are supposed to stop unless such sudden stopping is unsafe. Entering an intersection during the red signal is a citable offense, and several states are working to legalize video detection and enforcement using red light violation camera systems. Such enforcement is targeted toward driver behavioral modification; in the absence of an all-red interval the motorist who enters an intersection during the red signal runs an extremely high risk of being struck by cross-street traffic. A study was performed in the city of Detroit, Michigan, to compare the red light violation characteristics of intersections with properly designed all-red intervals and those intersections without all-red intervals. In the absence of before violation data, a comparative parallel experimental study was used. It was hypothesized that providing an all-red interval following a yellow change interval would reduce right-angle crashes. A before-and-after crash analysis was performed at the all-red-interval treatment sites (sites that targeted a reduction of right-angle and injury crashes). The analysis indicated significantly lower red light violations at the treatment sites. The analysis also indicated an extraordinary reduction in right-angle and injury crashes. This study demonstrated that substantial benefits, in terms of reducing red light violations and right-angle crashes, can be achieved by introducing a well-designed all-red interval.

Driver Behavior at Rail-Highway Crossings

A study of driver behavior at 37 rail-highway crossings in Michigan revealed the possible association between past crash histories and violations. Data collection included recording license plate numbers for violating vehicles, driver gender, approximate age of the driver, and the vehicle make and model. Driver violations were categorized into five different levels of severity ranging from routine to critical. The 37 study sites were subdivided into four groups based on crossing geometry and traffic control. The number of sites in the groups ranged from 5 to 18. Seven years of crash data on the study sites were considered for significance testing. Observed violation data for the same groups were calculated, and tests for statistical significance were performed on them. The results of this study indicated promise for the use of the violation data in determining the relative hazardousness of rail-highway crossings in combination with crash histories. The violation data may also be used to develop countermeasures that would help alleviate violations and eventually traffic crash problems at rail-highway crossing sites. Targeted enforcement as well should assist in driver behavioral modifications. Additionally, the timely arrival of trains after the warning devices are triggered is an essential element that motorists assess when considering taking risks.

Driving Simulator Validation for Nighttime Construction Work Zone Devices

Research was conducted to ascertain the validity of a driving simulator in determining the effectiveness of temporary traffic control devices in a work zone at night. The research was conducted through a field study and a simulator study. The field study examined speeds at six sites. The simulator study involved 127 human subjects. Spot speeds were observed at three locations in a freeway work zone. Locations of the speed studies were at the beginning of the work zone near the transition area, in the middle of the work zone, and at the end of the work zone near the downstream taper. Statistical analyses were conducted to determine whether participants of the study performed differently in the simulator, compared with in the field. Research results established that because of the motorists perceived risk of work zones, driving simulators may not replicate mean speeds observed in the field.

Operational performance measures of American roundabouts

The introduction of a new form of at-grade intersection control in the United States, termed a roundabout, has left many researchers and practitioners puzzled about their performance level. Many researchers and practitioners have looked to foreign design and operational manuals for guidance. Although the methods contained in these manuals have been implemented in their respective countries, no one is certain how they will transfer to conditions in the United States. Considering that driver characteristics are a major contributor to operational performance, these methods may not accurately depict the performance level of roundabouts with American drivers. Driver characteristics, in relation to operational performance, of four single-lane roundabouts located in the United States are described. The same driver characteristics are compared with findings in Australia under similar conditions; in addition, the probability density function for gap acceptance is derived. American drivers do not always react the same as Australian drivers under similar conditions. However, use of the Australian methods is, in most cases, more conservative and therefore should not overpredict the capacity and performance of roundabouts in the United States. The probability density function for gap acceptance at roundabouts was similar in shape and slope to that of two-way stop control. However, comparison of the gap-acceptance values of right-turning vehicles at two-way stop control with those at a roundabout indicates that drivers at roundabouts accept smaller gaps in the traffic stream on entry. This leads to the conclusion that roundabouts should perform better than two-way or all-way stop-controlled intersections under most conditions. The question remains: When do roundabouts function better than traffic signals?

CHANGE AND CLEARANCE INTERVAL DESIGN ON RED-LIGHT RUNNING AND LATE EXITS

Red-light violations (RLV) have been an ongoing concern to many engineering professionals, because a large portion of crashes that occur at signalized intersections involve red-light running and such crashes often result in injuries and fatalities. It has been estimated that in the United States, about 260,000 traffic crashes occur per year that involve drivers who run red lights, of which 750 are fatal. A before-and-after evaluation of the impacts in terms of RLV and late exits at signalized intersections was performed with a change and clearance interval calculated according to ITE guidelines. The study included three signalized intersections located in Oakland County, Michigan. RLV data were collected with video cameras at intersection approaches before and after implementation of the change, and clearance intervals were calculated according to ITE guidelines. The results of the before-and-after study on RLV indicated mixed results. At one of the study intersections, the RLV rates were reduced after the modified change and clearance intervals were installed. However, at the other two study locations, no significant differences were found in RLV rates in the before and after periods. The rates of late exits significantly decreased after installation of the test change and clearance intervals at all three study intersections. Therefore, the effects of implemented all-red clearance intervals were effective in reducing the opportunity and risk of late-exiting vehicles being exposed to oncoming traffic at the three study intersections.

Dynamic Late Lane Merge System at Freeway Construction Work Zones

In normal work zones with lane closures, drivers do not merge at any one definite point, a situation thus often causing a sudden interruption in traffic flow and sometimes higher delay and longer queue. The Dynamic Late Lane Merge System (DLLMS) is used to specify a definite merge point, improve the flow of congested work zones, and reduce queue lengths in travel lanes. The DLLMS was implemented in Michigan on three freeway segments that were reduced from two lanes to one lane because of highway construction work zones. The DLLMS directed traffic to use both lanes (open and closed lanes) until the designated “merge point” (close to the taper) where traffic from each lane was instructed to take turns merging into the open lane. On the basis of travel time characteristics, merge locations, and throughput, the effectiveness of the DLLMS was evaluated as a part of this study. The before period data were not available; therefore, a conventional work zone merge system, located on eastbound I-94, was used as a control site for the westbound I-94 test site. Comparison of the I-94 control and test sites indicated that the presence of the DLLMS improved the flow of travel and increased the percentage of vehicles that merged at or near the designated taper location. Based on the expected travel time savings, at a

Assessing Driver Distraction From Cell Phone Use: A Simulator-Based Study

5/h value of time, the benefit-cost ratio will be greater than 1, indicating that the monetary benefits of the DLLMS outweigh the cost of the system.

Implementation of Targeted Pedestrian Traffic Enforcement Programs in an Urban Environment

The relative driving performance of 37 drivers was compared in a controlled laboratory environment to assess how cell phone use affects driver performance on urban arterials and local roads. The stimulus consisted of answering a call on a hand-held cell phone and engaging in a scripted conversation with study researchers. A driving simulator replicated various typical real-world driving environments and roadway situations. Subjects drove a control scenario (baseline condition) and a test scenario in which they were asked to answer a set of questions using a hand-held cell phone while driving. The subjects were required to navigate various conditions, such as respond to traffic signs and signals, negotiate vehicular traffic when turning, and yield to unexpected pedestrians and bicyclists. Driver performance was assessed for overall driver performance scores, speed profiles, vehicular lateral placement within travel lanes, and number of crashes that occurred during the simulator experiment. Changes in measures between control and test scenarios were subjected to a series of statistical tests. Analysis results indicated that when cell phones were used while driving, subject performance scores were significantly lower, average speeds significantly slower, and proportions of improper lateral placement observed significantly higher. In addition, twice as many crashes (also statistically significant) were observed when subjects used cell phones while driving as were observed under the control condition. In this controlled laboratory experiment, the distraction caused by answering a call and engaging in a conversation on a hand-held cell phone significantly degraded driving performance.

Evaluation of Pedestrian Safety Educational Program for Elementary and Middle School Children

The purpose of this study was to develop, test, and evaluate two pilot enforcement programs aimed at the improvement of pedestrian safety in the city of Detroit, Michigan, through reductions in the incidence of pedestrian traffic violations. Separate targeted enforcement programs were conducted in coordination with the Detroit Police Department and the Wayne State University Police Department. Both programs demonstrated that targeted enforcement could be used to reduce the rate of pedestrian traffic violations effectively and that these changes could be sustained for some time after enforcement had been completed. The city-wide program was found to reduce violations by up to 17.1% during the enforcement period, with sustained reductions of 7.8% being detected several weeks after enforcement was completed. Similarly, the program on the Wayne State University campus reduced violations by 27% during enforcement and showed sustained reductions of 9.8%. The results generally varied on a case-by-case basis, and infrastructure deficiencies contributed to increased violations. As a part of this study, a strategy for collection of data in the field was developed. The strategy allowed the covert, unobtrusive monitoring of pedestrian behavior during the periods before, during, and after enforcement.

DRIVER BEHAVIOR CHARACTERISTICS AT URBAN SIGNALIZED INTERSECTIONS

A pedestrian safety educational program was presented to a total of 4,305 students ranging from kindergarten through 8th grade at 16 participating schools in Detroit, Michigan, between May 2008 and January 2009. The goal of the educational program was to improve student awareness of proper pedestrian behavior and street-crossing techniques, which the authors hypothesized would result in proper street-crossing behavior. This study improves on methodologies used in previous studies by performing an objective evaluation of the programs effectiveness, considering both message comprehension and natural street-crossing behavior of students at the schools where the program was implemented. Two measures of effectiveness were used for the program evaluation: (a) violation rate for child pedestrians observed before and after presentation of the program and (b) correct response rate obtained from written tests given before and after implementation. A total of 4,835 child pedestrians were observed during field data collection performed at 10 of the 16 schools. The child pedestrian violation rates were found to decrease in the after period at nine of the 10 schools where data were collected, with an overall decrease in violation rate of 4.44%, which was statistically significant at a 95% confidence level. Significant increases in the percentage of correct responses between the pre- and posttests were also observed at each of the schools and for all grade levels with the exception of kindergarten. The overall increase in correct response rate between the pre- and posttests was 23.2%, which was statistically significant.