There is currently no commonly accepted or adopted measure of pedestrian and bicycle exposure to risk. Consequently, a large portion of the field of pedestrian and bicycle safety is lacking an adequate means to evaluate the effectiveness of its efforts. The present paper presents a proposed new metric for measuring pedestrian and bicycle exposure to risk: hundred million pedestrian or bicycle miles of roadway (or other motor-vehicle shared facility) traveled. A method for implementing the proposed exposure metric is described for 8 shared facility types characteristic of the urban environment of Washington, DC. These facilities include three types of intersections, mid-block road segments, driveways, alleys, parking lots, parking garages, school areas and areas with playing/dashing/working in the roadway. The methodology is then used to calculate the annual pedestrian and bicycle exposure for the city for the calendar year 2007. The results of these calculations revealed 0.82 hundred million miles for pedestrian exposure and 0.37 hundred million miles for bicyclist exposure. In this wayboth the feasibility and scalability of the proposed metric were successfully demonstrated for a relatively large urban environment. Thus the proposed metric has the potential to eliminate one of the major obstacles in the pedestrian and bicycle safety field, the lack of adequate exposure data. While further refinement and validation are still needed, the proposed metric provides a possible initial foundation to develop a national unit of risk exposure for pedestrians and bicyclists.
Abstract