Shashi S Nambisan

Effectiveness of signal-based countermeasures for pedestrian safety: findings from pilot study

This paper summarizes findings from a pilot study to evaluate the effectiveness of signal-based countermeasures that may reduce conflicts and crashes and thereby enhance pedestrian safety. The countermeasures are pedestrian and driver oriented and consist of pedestrian-activated call buttons that light up to confirm activation, pedestrian countdown signals with animated eyes, and pedestrian-activated flashing yellow signals. The evaluations are based on field observations of pedestrian and driver behaviors before and after installation of the countermeasures at three sites (two intersections and one midblock location) in the Las Vegas, Nevada, metropolitan area. The countermeasures were evaluated with the following measures of effectiveness: pedestrians trapped in the roadway, signal cycles in which the call button was pushed, frequency of signal violation, pedestrians looking for vehicles before beginning to cross, pedestrians beginning their crossings during the “Walk” phase, pedestrians in the crosswalk at the end of the flashing “Dont Walk” phase, pedestrians who look for vehicles before crossing the second half of the street, captured pedestrians, diverted pedestrians (those who had to go out of their way to use the crosswalk or changed their course of action), drivers yielding to pedestrians, driver yielding or stopping distance before the crosswalk, drivers blocking the crosswalk, and drivers who come to a complete stop before making a right turn on red. The results showed improvements in pedestrians’ observational behavior for pedestrian-oriented countermeasures. Driver-oriented signal deployment improved the yielding behaviors of both drivers and pedestrians. These findings could be used to enhance pedestrian safety on arterial roads in other cities with similar demographic characteristics and traffic conditions.

Do Pedestrian Countdown Signals Influence Vehicle Speeds

The effects of pedestrian countdown signals on speeds of approaching vehicles as a function of the distance of the vehicle upstream of the intersection and the signal display are reported here. The analyses used mean speeds of vehicles on two segments immediately upstream of the stop bar and also during different indications of the pedestrian signal head (pedestrian “Walk” and pedestrian flashing “Dont Walk” signal with the time remaining in seconds to cross the street for the following intervals: greater than 15 s, 15 s to 10 s, 10 s to 5 s, and less than 5 s). Appropriate tests were performed to determine the statistical significance of the differences in observed mean speeds for each of these scenarios. Vehicle speeds were greater on the segment closer to the intersection than on the segment farther away. The speeds were also greater during the pedestrian countdown timer and flashing “Dont Walk” displays on the pedestrian signal head than when the pedestrian “Walk” signal and the countdown timer were displayed. All results were statistically significant at a 95% level of confidence except one, which had a 93% level of confidence. Results do not indicate that speeds are affected by the actual numeric displays on the countdown timer.

Effectiveness of Media and Enforcement Campaigns in Increasing Seat Belt Usage Rates in a State with a Secondary Seat Belt Law

Objective: In 2005, in terms of seat belt usage rates, Nevada ranked third nationally and first among states with secondary seat belt use enforcement laws in the United States. An effective combination of a media-based education and enforcement campaign helped in this regard. The objective of this article is to document the effectiveness of enforcement and media-based education and outreach campaigns on the seat belt usage rates in Nevada, a state with a secondary seat belt usage law Methods: Observational data on seat belt usage and passenger fatality data are used to evaluate the effectiveness of enforcement campaigns and media-based education and outreach campaigns. Data based on observations of about 40,000 vehicles in each of the years 2003 to 2005 were analyzed. Results: Statistical analyses show that a significant increase in seat belt usage rates among both drivers and passengers for both genders resulted from the accompanying the media and enforcement campaigns. Conclusions: The results from this study indicate that effective and well-planned media/enforcement campaigns can have a significant impact on seat belt usage rates even in a state where the enforcement of seat belt laws can only be as a secondary violation. They validate and expand on findings from other efforts documented in the literature. These results demonstrate that, if coordinated properly, media and enforcement campaigns work very effectively in increasing seat belt usage rates even in states with secondary seat belt laws.

Evaluating Effectiveness of Infrastructure-Based Countermeasures for Pedestrian Safety

This paper summarizes an evaluation of the effectiveness of selected infrastructure-based countermeasures to enhance pedestrian safety. The countermeasures evaluated in this paper were high-visibility crosswalk, median refuge, Danish offset, and pedestrian channelization. The selected countermeasures were deployed at eight locations in the Las Vegas, Nevada, metropolitan area. The evaluations were based on field observations of pedestrian and driver behaviors before and after the installation of the countermeasures. The selected countermeasures were evaluated with measures of effectiveness such as pedestrians who were trapped in the street, pedestrians who looked for vehicles before they began to cross, pedestrians who looked for vehicles before they crossed the second half of the street, pedestrians who were captured (those who modified their path to use the crosswalk but did not go out of their way to do so), pedestrians who were diverted (those who had to go out of their way to use the crosswalk or changed their course of action), drivers who yielded to pedestrians, the distance at which drivers yielded or stopped before the crosswalk, and drivers who blocked the crosswalk. Results showed that a high-visibility crosswalk and a median refuge helped to improve pedestrian as well as driver behavior, whereas a Danish offset increased the proportion of diverted pedestrians. At sites with those countermeasures, the distance at which drivers stopped or yielded for pedestrians before the crosswalk increased. Results based on analysis of data at the site with pedestrian channelization were inconclusive.

Age and Gender Differences in Conviction and Crash Occurrence Subsequent to Being Directed to Iowa's Driver Improvement Program

INTRODUCTIONnThis paper investigates potential gender and age differences in conviction and crash occurrence subsequent to being directed to attend Iowas Driver Improvement Program (DIP).nnnMETHODSnBinary logit models were developed to investigate the factors that influence conviction occurrence after DIP by gender and age. Because of the low crash occurrence subsequent to DIP, association rules were applied to investigate the factors that influence crash occurrence subsequent to DIP, in lieu of econometric models.nnnRESULTSnThere were statistical significant differences by driver gender, age, and conviction history in the likelihood of subsequent convictions. However, this paper found no association between DIP outcome, crash history, and crash occurrence.nnnIMPACT ON INDUSTRYnEvaluating the differences in conviction and crash occurrence subsequent to DIP between female and male drivers, and among different age groups can lead to improvements of the effectiveness of DIPs and help to identify low-cost intervention measures, customized based on drivers gender and age, for improving driving behaviors.

Determining Vehicle Operating Speed and Lateral Position Along Horizontal Curves Using Linear Mixed-Effects Models

Objective: Despite recent improvements in highway safety in the United States, serious crashes on curves remain a significant problem. To assist in better understanding causal factors leading to this problem, this article presents and demonstrates a methodology for collection and analysis of vehicle trajectory and speed data for rural and urban curves using Z-configured road tubes. Methods: For a large number of vehicle observations at 2 horizontal curves located in Dexter and Ames, Iowa, the article develops vehicle speed and lateral position prediction models for multiple points along these curves. Linear mixed-effects models were used to predict vehicle lateral position and speed along the curves as explained by operational, vehicle, and environmental variables. Behavior was visually represented for an identified subset of “risky” drivers. Results: Linear mixed-effect regression models provided the means to predict vehicle speed and lateral position while taking into account repeated observations of the same vehicle along horizontal curves. Conclusions: Speed and lateral position at point of entry were observed to influence trajectory and speed profiles. Rural horizontal curve site models are presented that indicate that the following variables were significant and influenced both vehicle speed and lateral position: time of day, direction of travel (inside or outside lane), and type of vehicle.

Effectiveness of Automatic Pedestrian Detection Device and Smart Lighting for Pedestrian Safety

A summary is given of an evaluation of the effectiveness of an automatic pedestrian detection device and a smart lighting system in improving pedestrian safety. These countermeasures were deployed at a midblock location in the Las Vegas metropolitan area in Nevada. The evaluations are based on field observations of pedestrian and motorist behaviors before and after the installation of the countermeasures. Their effectiveness was evaluated by using the following measures: percentage of pedestrians who looked to their left and right before and while crossing, percentage of pedestrians who changed their course of action, percentage of pedestrians trapped in the middle of the road, percentage of motorists who yielded to pedestrians, distance from the crosswalk at which motorists yielded to pedestrians, and delays. The results show an increase in pedestrians’ observational behavior and an improvement in motorists’ yielding behavior. A reduction in the number of pedestrians trapped in the roadway was also observed. Overall, the installation of the automatic pedestrian detection device and the smart lighting showed positive safety benefits for motorists’ and pedestrians’ behaviors at the test location. The findings from this study could be used to enhance pedestrian safety on arterial roads in other cities with similar demographic characteristics and traffic conditions.

Methods to Prioritize Pedestrian High-Crash Locations and Statistical Analysis of Their Relationships

This paper presents a summary of various methods that can be used to identify pedestrian high-crash locations (HCLs) and statistical evaluations of the relationship between the ranking methods. The indices and methods used to identify and rank pedestrian HCLs include individual methods such as crash indices based on frequency, weighted severity factor, vehicular traffic volume, and pedestrian age group, as well as composite methods such as the sum-of-the-ranks method and the crash score method. The ranks for individual HCLs obtained by these methods may vary, as they are based on different data. There is thus a need to evaluate the statistical relationships between the results obtained by the various methods. Data for 30 pedestrian HCLs in the Las Vegas, Nevada, metropolitan area were used to illustrate the methods and conduct statistical analyses. The results indicated that the rankings based on the individual methods were strongly correlated to the rankings from the composite methods, as were the rankings between the composite methods. The results also indicated that the rankings based on individual methods were correlated among themselves, although this correlation was not as strong. Furthermore, when only the top few highest-ranked HCLs were considered, their ranks were strongly correlated, regardless of the method chosen. Although any of the methods could be used to identify pedestrian HCLs, use of the simple frequency- or weighted frequency-based methods would be adequate as a first step.

Analyses of Vehicle Trajectories and Speed Profiles Along Horizontal Curves

Vehicle speed and lane position are two of the many possible factors that lead to crashes on horizontal curves. Vehicle position and speed through horizontal curves are of great relevance to many areas of traffic engineering, including countermeasure design, design consistency, and policy. This article discusses the results of an exploratory analysis of vehicle trajectories and speed profiles at two horizontal curves located in central Iowa. The sites include an urban and rural curve. Data were collected at five stations within the horizontal curves in both directions of travel using pneumatic road tubes set up in a Z-configuration. Overall, vehicles were found to cut the horizontal curve in the inside and outside travel lanes. However, the trajectories were seen to be different at the two curve sites. Vehicle mean speed profiles indicated that the curve site selected for evaluation operate differently and are reflected in the speed profiles. Speed deviations of individual vehicles as they traversed the curve were evaluated. More vehicles were found to adjust their speeds and lateral position in the vicinity of the center of the curve, and then at the end of the horizontal curve.

Impacts of Energy Regulations and Vehicular Technologies on Fuel Tax Revenues

Various energy regulations including corporate average fuel economy (CAFE) are forcing auto manufacturers and auto distributors to improve the fuel efficiency of vehicles significantly over the next decade. Conversely, improved automotive technologies and higher gasoline fuel prices enable better alternative-fuel vehicles (AFV), including hybrid vehicles (HV) and electric cars. This research evaluates the impacts of CAFE regulations in automobile and light truck fleet fuel economies, and effects of HV and AFV in the fleet, on gasoline-tax-based revenues. The new sales survivability (NSS) model, along with new vehicle sales data and vehicle survivability data from 1980 to 2005, were used to estimate the fleet mix, vehicle miles traveled (VMT) by fleet mix, and revenue projections through the year 2025. Five scenarios were considered to analyze the impacts of CAFE regulations and introduction of HV and AFV on fuel consumption and fuel-tax-based revenues for highway revenues. The results show that the CAFE regulation alone is expected to reduce the fuel-tax-based revenue by more than 21% in the year 2025. Similarly, the introduction of HV and AFV along with CAFE regulations is expected to reduce fuel-tax-based revenues by more than 31 and 37%, respectively, in the year 2025. This paper shows the significance of considering the effects of new regulations and technological improvements in estimating future fuel-based revenues. The revenue estimated in this paper is much lower than the estimates developed by previous studies. This shows that modifications to the existing system of highway financing would be required much earlier than anticipated.