Abstract:
A research effort was undertaken by the Baltimore Metropolitan Council, Maryland, to explore further the relationship between land use and transportation to support regional planning analysis. Particular attention was given to quantifying the role of key land use factors such as density, diversity, and design (3Ds) and regional accessibility in determining rates of vehicle ownership and vehicle miles traveled (VMT). The research was facilitated by a recent regional household travel survey and significant untapped geographic information system (GIS) resources. What began as an effort simply to replicate the approach of an earlier published study that incorporated the 3Ds took an unexpected turn. The result was an entirely new measure, a walk opportunities index, which combines information on the number, character, and desirability of key activities located within walking distance of a household. GIS procedures were used to trace walk paths to each destination by using the street grid and to compute travel times while adjusting for topography and difficult street crossings. By using the gravity model paradigm, each opportunity was then discounted by its travel time and the results summed into a single measure of walk opportunities. When used in combination with measures of entropy, regional accessibility, and socioeconomic characteristics, this new index had important statistical value in regression models of household auto ownership and VMT. The ability of these models to address the travel effects of alternative transportation and land use development plans or policies makes them a potentially powerful tool in regional planning activities.
