#02 - Cross Walk Discussion - Laserfiche WebLink

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16 report. All treatment (crosswalk) and comparison sites were chosen without prior knowledge of crash history. All sites used in this study were intersection or midblock locations with no traffic signals or stop signs on the main road approach (i.e., uncontrolled approaches). This study focused on pedestrian safety and, therefore, data were not collected for vehicle-vehicle or single-vehicle collisions, even though it is recognized that marking crosswalks may increase vehicle stopping, which may also affect other collision types. The selected analysis techniques were deemed to be appropriate for the type of data in the sample. Due to relatively low numbers of pedestrian crashes at a given site (many sites had zero pedestrian crashes in a 5- year period), Poisson modeling and negative binomial regression were used to analyze the data. Using these analysis techniques allowed determination of statistically valid safety relationships. In fact, there were a total of 229 pedestrian crashes at the 2,000 crossing sites over an average of 5 years per site. This translates to an overall average of one pedestrian crash per crosswalk site every 43.7 years. While this rate of pedestrian crashes seems small on a per-site basis, it must be understood that many cities have hundreds or thousands of intersections and midblock locations where pedestrians regularly cross the street. Considering that pedestrian collisions with motor vehicles often result in serious injury or death to pedestrians, it is important to better understand what measures can be taken by engineers to improve pedestrian safety under various traffic and roadway conditions. All analyses of crash rates at marked and unmarked crosswalks took into account traffic volume, pedestrian exposure, and other roadway features (e.g., number of lanes). To supplement the pedestrian crash analysis, a corresponding study was conducted on pedestrian and driver behavior before and after marked crosswalks were installed at selected sites in California, Minnesota, New York, and Virginia, as discussed earlier.(13,14) Statistical Techniques The Poisson and negative binomial regression modeling were conducted in two ways in terms of how the comparison sites were handled. These were: • Including all of the comparison (unmarked) crosswalk sites in one group and all of the treated (marked) crosswalks in another group. In other words, no direct matching of sites was used in the modeling. • Analyzing 1,000 site pairs; each pair had a marked crosswalk and an unmarked, matched comparison site. Analyses were conducted using both assumptions to insure that the results were not influenced merely by the manner in which the matching was conducted. The analyses revealed very similar results using either of the assumptions listed above in terms of: • The variables found to be significantly related to pedestrian crashes. • The individual and interaction effects. • The magnitude of the effects of each traffic and roadway variable on pedestrian crashes, including the effect of marked versus unmarked crosswalks.