Urban sprawl as a risk factor in motor vehicle occupant and pedestrian fatalities

Objectives. We sought to determine the association between urban sprawl and traffic fatalities. Methods. We created a sprawl index by applying principal components analysis to data for 448 US counties in the largest 101 metropolitan areas. Regression analysis was used to determine associations between the index and traffic fatalities. Results. For every 1% increase in the index (i.e., more compact, less sprawl), all-mode traffic fatality rates fell by 1.49% (P<.001) and pedestrian fatality rates fell by 1.47% to 3.56%, after adjustment for pedestrian exposure (P<.001). Conclusions. Urban sprawl was directly related to traffic fatalities and pedestrian fatalities. Subsequent studies should investigate relationships at a finer geographic scale and should strive to improve on the measure of exposure used to adjust pedestrian fatality rates.