How do the definitions of urban and rural matter for transportation safety? Re-interpreting transportation fatalities as an outcome of regional development processes.

Urban and rural places are integrated through economic ties and population flows. Despite their integration, most studies of road safety dichotomize urban and rural places, and studies have consistently demonstrated that rural places are more dangerous for motorists than urban places. Our study investigates whether these findings are sensitive to the definition of urban and rural. We use three different definitions of urban-rural continua to quantify and compare motor vehicle occupant fatality rates per person-trip and person-mile for the state of Wisconsin. The three urban-rural continua are defined by: (1) popular impressions of urban, suburban, and rural places using a system from regional economics; (2) population density; and (3) the intensity of commute flows to core urbanized areas. In this analysis, the three definitions captured different people and places within each continuum level, highlighting rural heterogeneity. Despite this heterogeneity, the three definitions resulted in similar fatality rate gradients, suggesting a potentially latent "rural" characteristic. We then used field observations of urban-rural transects to refine the definitions. When accounting for the presence of higher-density towns and villages in rural places, we found that low-density urban places such as suburbs and exurbs have fatality rates more similar to those in rural places. These findings support the need to understand road safety within the context of regional development processes instead of urban-rural categories.