Characteristics of Pedestrian Risk in Darkness

Source: The University of Michigan Transportation Research Institute

In this report, we examined different types of pedestrian crashes to discover which characteristics of those crashes produced increased risk. In particular, we looked at roadway function and posted speed limit, because we expected that in high-speed environments, the risk to pedestrians in darkness may be especially high. In darkness, the driver's forward view is constrained by the reach of the vehicle's headlamps. Because this distance is the same regardless of vehicle speed, the faster the vehicle is moving, the smaller the time interval between detecting an object in the vehicle's path and potentially colliding with that object. With progressively smaller amounts of time to react, we should expect to see more failure to avoid pedestrians.

The risk analysis was then coupled with annual counts of fatalities in darkness using the same crash types to identify the overall magnitude of the problem. This magnitude was used to make projections of the potential number of lives saved if darkness could be turned into daylight. By combining the risk estimate and the annual fatality level, we can obtain some guidance about where light is most needed on the roadway. In addition, we extended the analysis of the relationship between darkness and alcohol that was begun by Owens and Sivak (1993). In that report, they examined alcohol use by drivers and found that it did not seem to contribute to fatal pedestrian crashes. In this study we investigated the consequences of alcohol use by pedestrians as well as drivers.

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