Herman Huang

Safety Effects of Marked Versus Unmarked Crosswalks at Uncontrolled Locations: Analysis of Pedestrian Crashes in 30 Cities

Pedestrians are legitimate users of the transportation system and they should, therefore, be able to use the system safely. Pedestrian needs in crossing streets should be identified, and appropriate solutions should be selected to improve pedestrian safety and access. Deciding where to mark crosswalks is only one consideration in meeting that objective. This study involved an analysis of 5 years of pedestrian crashes at 1,000 marked crosswalks and 1,000 matched unmarked comparison sites. None of the sites in this study had a traffic signal or stop sign on the approaches. Detailed data were collected on traffic volume, pedestrian exposure, number of lanes, type of median, speed limit, and other site variables. Poisson and negative binomial regressive models were used. Study results revealed that on two-lane roads the presence of a marked crosswalk alone at an uncontrolled location was associated with no difference in pedestrian crash rate, compared with an unmarked crosswalk. Further, on multilane roads with traffic volumes above about 12,000 vehicles per day, having a marked crosswalk was associated with a higher pedestrian crash rate (after controlling for other site factors) compared with an unmarked crosswalk. Raised medians provided significantly lower pedestrian crash rates on multilane roads, compared with roads without a raised median. Older pedestrians had crashes that were high relative to their crossing exposure. More substantial improvements were recommended to provide for safer pedestrian crossings, including adding traffic signals (with pedestrian signals) when warranted, providing raised medians, and implementing speed-reducing measures.

EFFECTS OF TRAFFIC CALMING MEASURES ON PEDESTRIAN AND MOTORIST BEHAVIOR

By slowing down vehicle traffic, shortening crossing distances, and enhancing motorist and pedestrian visibility, traffic calming treatments may benefit pedestrians who are crossing the street. The effects of selected traffic calming treatments on pedestrian and motorist behavior were evaluated at both intersection and midblock locations. Before and after data were collected in Cambridge, Massachusetts (bulbouts and raised intersection), Corvallis, Oregon (pedestrian refuge island), Seattle, Washington (bulbouts), and Sacramento, California (refuge islands). The key findings include that none of the treatments had a significant effect on the percentage of pedestrians for whom motorists yielded, the treatments usually did not have a significant effect on average pedestrian waiting time, and refuge islands often served to channelize pedestrians into marked crosswalks. The raised intersection in Cambridge also increased the percentage of pedestrians who crossed in the crosswalk. While traffic calming devices have the potential for improving the pedestrian environment, these devices by themselves do not guarantee that motorists will slow down or yield to pedestrians.

Evaluation of lane reduction road diet measures on crashes and injuries

“Road diets” are often conversions of four-lane undivided roads into three lanes (two through lanes plus a center turn lane). The fourth lane may be converted to bicycle lanes, sidewalks, or on-street parking. Road diets are sometimes implemented with the objective of reducing vehicle speeds as well as the number of motor vehicle crashes and injuries. A study was conducted to investigate the actual effects of road diets on motor vehicle crashes and injuries. Twelve road diets and 25 comparison sites in California and Washington cities were analyzed. Crash data were obtained for these road diet (2,068 crashes) and comparison sites (8,556 crashes). A “before” and “after” analysis using a “yoked comparison” study design found that the percent of road diet crashes occurring during the “after” period was about 6% lower than that of the matched comparison sites. However, a separate analysis in which a negative binomial model was used to control for possible differential changes in average daily traffic, study period, and other factors indicated no significant treatment effect. Crash severity was virtually the same at road diets and comparison sites. There were some differences in crash type distributions between road diets and comparison sites, but not between the “before” and “after” periods. Conversion to a road diet should be made on a case-by-case basis in which traffic flow, vehicle capacity, and safety are all considered. It is also recommended that the effects of road diets be further evaluated under a variety of traffic and roadway conditions.

Bicyclist Intersection Safety Index

Each year many bicyclists are injured or killed in intersection-related crashes with motor vehicles. The objective of this study was to develop a macrolevel bicycle intersection safety index (Bike ISI) that would allow engineers, planners, and other practitioners to use known intersection characteristics to prioritize intersection approaches with respect to bicycle safety proactively. Using variables that indicate a higher probability of risk for bicyclists, the Bike ISI identifies which intersection approaches have the highest priority for bicycle safety improvements within a particular jurisdiction. Using video data and online ratings surveys, this study obtained data on avoidance maneuvers and safety ratings at 67 intersection approaches and developed a Bike ISI model that incorporated both measures of safety. The Bike ISI uses data on the traffic volume, the number of lanes, the speed limit, the presence of a bike lane, the presence of parking, and the presence of traffic control to give a rating for an intersection approach according to a six-point scale. Using the Bike ISI, practitioners have the ability to evaluate each approach at all intersections in their jurisdictions or at a select group of intersections. Once safety index values are assigned to each site, the practitioner can then select the sites with the highest index values and conduct more detailed reviews of those sites to determine whether any treatments are needed to improve the safety of the intersection.

Effects of Innovative Pedestrian Signs at Unsignalized Locations: Three Treatments

Three types of devices that have been used in conjunction with marked crosswalks in an attempt to improve pedestrian safety were evaluated: an overhead crosswalk sign in Seattle, Washington; pedestrian safety cones (which read, “State Law: Yield to Pedestrians in Crosswalk in Your Half of Road”) in New York State and in Portland, Oregon; and pedestrian-activated overhead signs (which read, “Stop for Pedestrians in Crosswalk”) in Tucson, Arizona. The signs were used under varying traffic and roadway conditions. The effects of these three treatments on pedestrian and motorist behavior were evaluated. The variables of interest were whether pedestrians had the benefit of motorists yielding to them; whether pedestrians had to run, hesitate, or abort their crossing; and whether pedestrians crossed in the crosswalk. The New York cones and Seattle signs were effective in increasing the numbers of pedestrians who had the benefit of motorists yielding to them. At one location in Tucson, the overhead sign increased motorist yielding to pedestrians. The signs in Seattle and Tucson were effective in reducing the number of persons who had to run, hesitate, or abort their crossing. None of the treatments had a clear effect on whether people crossed in the crosswalk. By themselves, these devices cannot ensure that motorists will slow down and yield to pedestrians. It is essential to use these and other devices along with education and enforcement, but creation of friendlier pedestrian environments (e.g., by means of implementing geometric improvements) for the purpose of reducing vehicle speeds may be more important.

THREE-STRAND CABLE MEDIAN BARRIER IN NORTH CAROLINA: IN-SERVICE EVALUATION

By using historical crash data, several regression-type models were developed with which to estimate the effects of the installation of cable median barrier on crash rates for several crash types while taking into account several other factors associated with variation in crash occurrences or crash rates. The data for these analyses consisted of counts of crashes of the various types for each section of North Carolina Interstate highway, along with the associated roadway characteristics, for 1990 through 1997. Certain roadway characteristics (in particular, traffic volume) changed from year to year as, of course, did the crash counts. The entire North Carolina Interstate system was taken as a reference population; a negative binomial error structure was assumed for many of the models, and the models contained specific effects for each crash year to account for various unmeasured effects that may vary from year to year (e.g., weather conditions). These models used the reference population to predict numbers of crashes on the cable sections. After cable barrier installation, none of these crashes occurred. In summary, these analyses indicate that several types of crashes (e.g., ran-off-road-left, hit-fixed-object) increased on the sections where cable median barrier was installed. However, these sections showed improved overall safety through fewer serious and fatal crashes as well as fewer head-on crashes. Overall severity index values were greatly reduced after cable barrier installation.

Index for Assessing Pedestrian Safety at Intersections

The primary objective of this study was to develop an index that would allow engineers, planners, and other practitioners to prioritize intersection crosswalks with respect to pedestrian safety. The study involved collecting data on pedestrian crashes, conflicts, and avoidance maneuvers as well as subjective ratings of intersection video clips by pedestrian professionals. Sixty-eight pedestrian crosswalks were selected for the pedestrian analysis from Philadelphia, Pennsylvania; San Jose, California; and Miami-Dade County, Florida. A predictive model, the pedestrian intersection safety index (Ped ISI), was developed primarily on the basis of intersection ratings and avoidance maneuvers. Variables in Ped ISI included the number of through lanes, 85th percentile vehicle speed, type of intersection control (signal or stop sign), main street traffic volume, and area type. Through a user-friendly guide, Ped ISI can be used to identify which crosswalks in a city have the highest priority for pedestrian safety i...

AUTOMATED DETECTION OF PEDESTRIANS IN CONJUNCTION WITH STANDARD PEDESTRIAN PUSH BUTTONS AT SIGNALIZED INTERSECTIONS

Automated pedestrian detection systems provide the means to detect the presence of pedestrians as they approach the curb prior to crossing the street, and then these systems call the Walk signal without any action required on the part of the pedestrians. These detectors can also extend the clearance interval in order to allow slower persons to finish crossing. Whether automated pedestrian detectors, when used in conjunction with standard pedestrian push buttons, would result in fewer overall pedestrian-vehicle conflicts and fewer inappropriate crossings (i.e., pedestrians’ beginning to cross during a Don’t Walk signal) was evaluated. Before and after video data were collected at intersection locations in Los Angeles, California (infrared and microwave), Phoenix, Arizona (microwave), and Rochester, New York (microwave). The results indicated a significant reduction in vehicle-pedestrian conflicts, as well as a reduction in the number of pedestrians beginning to cross during the Don’t Walk signal. The differences between microwave and infrared detectors were not significant. Detailed field testing of the microwave equipment in Phoenix revealed that fine-tuning of the detection zone is still needed in order to reduce the number of false calls and missed calls.

Effects of a Towaway Reporting Threshold on Crash Analysis Results

The effects on future data analysis capabilities and results should states convert to a towaway and above crash-reporting threshold are quantified. The results from the four states used in the analysis (Illinois, Michigan, Minnesota, and North Carolina) revealed that only 51.7 percent of the crash data would be included using a towaway threshold. Only 33.7 percent would be included using an injury threshold. In general, a towaway threshold would exclude more crashes on urban streets than on rural roads. For most road classes, 40 to 60 percent of crashes would be excluded. A towaway threshold would result in greatly underestimating the occurrence of certain crash types, particularly rear-end, sideswipe, parking, and animal crashes. Run-off-road and angle/turning crashes would also be affected considerably. Using a towaway criterion will seriously affect researchers’ ability to conduct meaningful evaluations of roadside appurtenances, such as guardrail, breakaway signs and poles, crash cushions, and various median treatments. For most vehicle types, only 30 to 60 percent of crashes would be included under a towaway threshold. Technological, institutional, and organizational strategies for improving crash reporting thresholds are suggested.

PREVENTION OF MOTOR VEHICLE INJURIES TO ELDERLY PEDESTRIANS

This article is based on a study conducted for the Centers for Disease Control by the University of North Carolinas (UNC) Highway Safety Research Center. The article begins by presenting background material on the older pedestrian and the causes and characteristics of older pedestrian injuries. A summary is then provided of the results of analyzing more than 26,000 pedestrian-motor vehicle crashes occurring in North Carolina during an 11-year period (1980-1990). Included in the total are 1,758 pedestrian victims age 65 or older. Similar findings are reported from an analysis of 70,825 fatal pedestrian-motor vehicle crashes occurring nationwide from 1980 to 1989 and identified from the Fatal Accident Reporting System (FARS) database. Education programs, pedestrian laws, and roadway improvements are interventions which may reduce motor vehicle injuries and deaths to elderly pedestrians.