Timothy J. Gates

Dilemma zone driver behavior as a function of vehicle type, time of day, and platooning

A comprehensive investigation of the influence of vehicle type on various aspects of dilemma zone driver behavior, including brake response time, deceleration rate, and red light running occurrence, was performed at six urban or suburban signalized intersections in Wisconsin. Driver behavior data were obtained for 1,275 vehicles that were between 2.0 and 6.5 s upstream of the intersection at the onset of the yellow interval. Each vehicular observation was classified into one of five vehicle type categories: motorcycle, car, light truck (pickup, SUV, van, minivan), single-unit truck (single-unit heavy truck, delivery truck, recreation vehicle, bus), and tractor trailer (multiunit heavy truck). Each observation was also classified by time of day and whether the subject vehicle was part of a platoon. Vehicle type had a statistically significant effect on deceleration rate and red light running occurrence but did not have an effect on brake response time. Deceleration rates were highest for cars and light trucks; single-unit trucks and tractor trailers showed the lowest deceleration rates. Tractor trailers were 3.6 times more likely and single-unit trucks were 2.5 times more likely to commit red light running compared with passenger vehicles. The rates of red light running for cars and light trucks were not substantially different from each other. Time of day (peak versus off-peak) had a statistically significant effect on both deceleration rate and occurrence of red light running. Deceleration rates were significantly higher during off-peak times. Red light running was 1.3 times more likely to occur during peak periods compared with off-peak periods. Platooning had no effect on any of the measures of effectiveness.

Effectiveness of Experimental Transverse-Bar Pavement Marking as Speed-Reduction Treatment on Freeway Curves

Researchers performed a before-and-after analysis of speeds to determine the short- and long-term effectiveness of an experimental transverse-bar pavement marking treatment at the Plainfield curve on I-43–I-94 in Milwaukee, Wisconsin. The experimental transverse pavement marking treatment was installed in all lanes for each of the northbound and southbound directions of the curve in early September 2006. Each section of the pavement marking treatment was 1,000 ft long. The treatment sections consisted of a series of white transverse-bar markings installed with continuously decreasing spacing between successive markings, giving drivers the perception of increasing speed, potentially causing them to slow down. Each individual marking was 18 in. in lateral width by 12 in. longitudinally. Speed data were collected for 2 weeks in late July 2006; again in September 2006, approximately 1 week after the markings had been installed; and again in March 2007, approximately 6 months after the markings had been installed (northbound only). The researchers used analysis of variance to analyze the mean speeds for more than 43,000 intervals of 5 min each measured at three locations in each lane of the northbound and the southbound directions. The results of the analysis suggest that the experimental transverse pavement marking treatment was effective at reducing curve speeds, especially shortly after installation. The marking treatment showed the greatest effects on speeds midway through the treatment section with approximately 1- to 4-mph reductions in mean speed observed between the before and the after periods. A lane-by-lane analysis showed that the marking treatment was most effective at reducing speeds in the shoulder and middle lanes, while speeds in the median lane were relatively unaffected.

Guidelines for Timing Yellow and Red Intervals at Signalized Intersections

The lack of a national standard, recommended practice, or set of guidelines for determining the duration of the yellow change and red clearance intervals for the timing of traffic signals has left each transportation agency to determine its own practices. The objective of NCHRP Project 03–95 was to develop a comprehensive and uniform set of recommended guidelines for determining safe and operationally efficient yellow and red intervals at signalized intersections. To accomplish this objective, the study established a state of knowledge and a state of practice through a review of existing guidelines and various literature sources and a survey of transportation agency practitioners. The research also conducted a comprehensive national investigation of driver behavioral characteristics through an extensive field data collection and analysis effort. These efforts confirmed the accepted values for perception–reaction time (1.0 s) and deceleration rate (10 ft/s2) and established 85th percentile speed estimations for through and left-turning vehicles. Justification was also provided for accounting for start-up delay. From the findings, a succinct recommended guideline for the timing of yellow change and red clearance intervals was formulated on the basis of a kinematic equation and its associated variable values. The recommended guideline encourages a uniform practical application that provides a framework that can be easily adopted into transportation agency practice.

Comprehensive Evaluation of Driver Behavior to Establish Parameters for Timing of Yellow Change and Red Clearance Intervals

In 2009, NCHRP Project 03–95 sought to develop a comprehensive, uniform set of recommended guidelines for determining safe and operationally efficient yellow change and red clearance (i.e., all-red) intervals at signalized intersections. Before guideline development, a comprehensive field study of driver behavior was performed to establish the three primary parameters found in a commonly used kinematic equation (the ITE equation): perception–reaction time, deceleration rate, and approach speed. To provide broad nationwide representation of driver characteristics, site conditions, and traffic signal timing practices, 83 study approaches were evenly selected from four regions of the United States: Southeast Michigan, Central Florida, Southern California, and Greater Washington, D.C. Driver behavior data were collected at each site with an elevated high-definition video camera. The resulting data set included 2,458 first-to-stop dilemma zone vehicles that were less than 5.5 s upstream of the intersection at the start of the yellow interval. The studys overall mean brake response time of 1.00 s was identical to ITEs recommended default value of 1.0 s for timing of the yellow interval, and the overall mean deceleration rate of 10.08 ft/s2 was very close to ITEs recommended deceleration rate of 10 ft/s2. The study determined that the 85th percentile speed of free-flowing through-moving vehicles approaching a signalized intersection may be accurately estimated by adding 7 miles per hour (mph) to the posted speed limit on the approach. Similarly, the 85th percentile approach speed for free-flowing left-turning vehicles may be accurately estimated by subtracting 5 mph from the posted speed limit.

Longitudinal Analysis of Rural Interstate Fatalities in Relation to Speed Limit Policies

Existing research literature has shown that traffic fatalities increase at higher speed limits. A related issue is the establishment of maximum speed limits for trucks and buses. As of 2014, eight states have a differential speed limit in place that establishes a higher limit for passenger vehicles than for trucks and buses. This study aimed to inform the continuing debate regarding the safety impacts of speed limits by comparing states with various speed limit policies. The study included a longitudinal comparison of state-level rural Interstate fatalities in the United States from 1999 through 2011. In addition to an examination of differences in traffic fatalities as a function of maximum speed limits, comparisons were also made between states with differential limits for truck and buses. Random parameter negative binomial models were estimated for annual total and truck-involved fatalities. A random parameter framework allowed for consideration of temporal correlation in annual fatality counts within states as well as for unobserved heterogeneity across states. The results of this study provided further evidence that both overall and truck-involved fatalities increased with maximum speed limits. States with differential speed limits were found to have marginal differences in total fatalities as compared with states with uniform speed limits. However, truck-involved fatalities were significantly lower in states where differential limits were in place. The effects of speed limit policies as well as other covariates were found to vary significantly across states. The random parameter models demonstrated significantly improved goodness of fit as compared with standard Poisson and negative binomial models.

Implementation of Targeted Pedestrian Traffic Enforcement Programs in an Urban Environment

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.

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

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.

Spatial Analysis of Child Pedestrian and Bicycle Crashes: Development of Safety Performance Function for Areas Adjacent to Schools

Pedestrian and bicycle safety for school-aged children is a particular concern as traffic crashes continue to be a leading cause of death for children 5 to 14 years old. For this concern to be addressed, Safe Routes to School (SRTS) programs have been implemented in communities across the country, with one of the primary objectives being to provide safe and convenient routes for children to walk or bike to school. Unfortunately, SRTS programs allocate limited funding for such projects. Consequently, it is imperative that programs are implemented at locations where they are likely to have the greatest impact. The primary focus of this study was to develop a safety Performance function (SPF) for use in prioritizing candidate schools for SRTS programs. Traffic crashes over a 5-year analysis period were examined and linked to data that included the school enrollment, the socioeconomic and demographic data for each school district, and the functional class of the roadway on which each school was located. Schools on local roads were found to experience more crashes than those located on other, higher-class road facilities. Crashes also varied with average family size, number of parents per household, population density, and median family income. Crashes were less frequent in school districts that exhibited greater ethnic diversity. The SPF developed as a part of this research can be used for prioritization of candidate schools as well as to assess the efficacy of SRTS programs on a longitudinal basis and thus provide a valuable tool for school administrators and others involved in child pedestrian and bicycle safety.

Disaggregate-Level Assessment of Changes to Michigan's Motorcycle Helmet Use Law: Effects on Motorcyclist Injury Outcomes

On April 13, 2012, Michigan instituted reforms to its long-standing universal helmet law (UHL) and thus became the 28th state with a partial helmet law, which requires helmet use by only a subset of the riding population. Given continuing increases in motorcycle fatalities, helmet use remains a divisive policy issue facing state governments. The existing research literature includes several before-and-after studies that evaluate the effects of changes in motorcycle helmet laws on metrics such as helmet use and statewide motorcycle fatalities. However, a comprehensive assessment of the effects of helmet use laws on the full range of crash injury outcomes is lacking. Important evidence was added to inform the continuing debate about the efficacy of UHLs. A detailed, disaggregate-level study was conducted to assess the degree of injury severity sustained by motorcyclists involved in crashes before and after Michigans transition from a UHL to a partial helmet law. By controlling for various rider, roadway, traffic, and weather characteristics, results of the study demonstrate that helmets reduced the probability of fatalities by more than 50%. Injuries tended to be less severe in crashes that involved deer, occurred at lower speeds, or occurred in inclement weather but more severe in high-speed collisions or when drugs and alcohol were involved. The riders who tended to be more susceptible to severe injury were female, younger (age 21 to 30 years), or older (age 51 to 70 years).

ECONOMIC ASSESSMENT OF PUBLIC REST AREAS AND TRAVELER INFORMATION CENTERS ON LIMITED ACCESS FREEWAYS

Public rest areas along limited-access freeways throughout the United States allow quick access and free 24-h availability to basic amenities such as parking and restrooms. The recent economic downturn has made it increasingly difficult for state agencies to maintain rest areas and has forced many states to consider downsizing services or closing facilities. Although rest areas provide many benefits to motorists, the safety and economic impacts associated with rest areas and traveler information centers have proved difficult to quantify. A benefit–cost (B-C) analysis methodology was developed for public rest areas and traveler information centers on limited-access freeways. This methodology considered a broad range of benefits associated with public rest areas, including travel diversion savings, comfort and convenience benefits, and crash reductions. Increased tourism spending was also considered for traveler information centers. The costs were almost exclusively related to those incurred by the agency, which included construction, rehabilitation, operation, and routine maintenance. The methodology was demonstrated with data provided by the Michigan Department of Transportation. Because the estimated benefits were strongly correlated with annual use of the facility, the facilities with the highest B-C ratios included heavily used facilities located on the primary freeway routes. Those with the lowest B-C ratios were underused facilities with high operation or maintenance costs.