Kerrie L Schattler

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.

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.

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.

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

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.

DRIVER BEHAVIOR CHARACTERISTICS AT URBAN SIGNALIZED INTERSECTIONS

Red-light running and the associated risk of severe crashes at signalized intersections have been an ongoing concern to many safety professionals. The proportions of crashes that occur due to such driver behavior represent a substantial number of crashes at urban and suburban signalized intersections in Michigan. In the year 2001, crashes related to red-light running in Michigan represented about 28% of the crashes of all severities and 40% of fatal and serious injury crashes occurring within signalized intersections. Many initiatives to discourage red-light running have been used in the United States with various degrees of success. Such programs include public awareness campaigns, automated enforcement programs, and some engineering countermeasures. These initiatives have resulted in some reduction in the overall crash statistics in the communities where such programs have been implemented. A series of evaluation studies was performed in Michigan to test the effectiveness of implementing change and clearance intervals calculated according to ITE guidelines on late exits and red-light violations at nine signalized intersections in the Detroit metropolitan area. The study described used four approaches at four test intersections where engineering treatments have been applied (16 total test sites) and four approaches at five control intersections. Driver behavior was examined at test and control intersections by observing and quantifying the number of vehicles that did not clear the intersection when the cross-street signal light turns green (late exit) and red-light violations. Upon analysis, red-light-running data at the test and control sites did not exhibit a significant difference. However, the test sites showed significantly lower late exit rates compared with the control sites, thus lowering the risk of right-angle crashes.

Effective Safety Improvements Through Low-Cost Treatments

A vast majority of traffic crashes in urban areas occur at signalized intersections. Roadway geometry, traffic control, adjacent land uses, and environmental factors at intersections often contribute to the high incidence of traffic crashes and injuries. A public-private partnership project to identify high-crash and high-risk locations in the city of Detroit was initiated in 1996. Eighteen candidate sites were selected, and an extensive engineering study was conducted to develop countermeasures to help alleviate the traffic crash problem at the selected sites. The Automobile Association of America, Michigan, was the private partner in this joint venture and, in partnership with the city of Detroit, was a major contributor to covering the cost of improvements. The selection of countermeasures was based on state-of-the-art methodology and analysis, and implementation of the selected countermeasures at some of the sites was undertaken as the initial phase of the project. A comprehensive before-and-after evaluation study was performed at three of the improved sites. The study revealed that the safety improvements that were implemented lowered both crash and severity experience. The differences between the before and after crash frequencies proved to be statistically significant. Additionally, a benefit-cost analysis at the study locations indicated extraordinary results. This research presents the evaluation study results and discusses the countermeasures and improvements that were the most successful in mitigating traffic crash problems at the selected study locations.

Safety Performance of Flashing Yellow Arrow for Protected–Permissive Left-Turn Signal Control in Central Illinois

In 2010, the Illinois Department of Transportation began implementing the flashing yellow arrow (FYA) at intersections operating with protected–permissive left-turn (PPLT) control. Research was conducted to evaluate the safety-effectiveness of FYAs at 86 intersections and 164 approaches in central Illinois. The effectiveness evaluation was performed with 3 years of before-and-after FYA installation crash data and the empirical Bayes method. In the before condition, the left-turn signals operated with a circular green display indicating the permissive interval of PPLT control using a five-section signal head. In the after condition, the FYA replaced the circular green display for the permissive interval of PPLT with a four-section signal head. Supplemental traffic signs were mounted on the mast arm adjacent to the left-turn signal at over half of the FYA installations. The results of the comprehensive safety evaluation of the FYA for PPLT control are presented. Analyses were also performed to assess the effects of the FYA supplemental signs and the effects of the FYA overall on two subsets of at-fault drivers: older drivers (age 65+) and younger drivers (age 16 to 21). The resulting mean crash modification factors for the targeted crash types ranged from 0.589 to 0.714. The findings of this research support the continued use of FYAs for PPLT control to improve safety at signalized intersections in central Illinois.