Tech Report

District of Columbia. Dept. of Transportation

Mixed-use development has become increasingly common across the country, including Washington, D.C. However, a straightforward and empirically validated method for evaluating the traffic impacts of such projects is still needed. The data presented in the Institute of Traffic Engineers (ITE) Trip Generation informational report is primarily collected at suburban, single-use, and free-standing sites. This defining characteristic limits the applicability of these basic trip rates to mixed-use or multi-use development projects. While the number of person trips generated by individual uses may be similar to free-standing sites, the potential for interaction among on-site activities can significantly reduce the total number of vehicle trips. Additionally, mixed-use projects located in areas with a variety of nearby destinations and high quality transit access will produce fewer vehicle trips due to a larger share of trips entering and exiting the site on foot, bicycle, or by transit. The Mixed-Use Development (MXD+) method, initially developed for the United States Environmental Protection Agency (EPA) and ITE, accounts for the degree to which mixed-use sites internally capture travel and the extent to which smart growth site design and context result in walking, biking, and transit use. The EPA MXD+ method represents a dramatic improvement over current methods of estimating trip generation for mixed-use developments. The method produces reliable, though still somewhat conservative, estimates of trip generation that are highly sensitive to the context of any given development. The District of Columbia Department of Transportation (DDOT) has long recognized the deficiencies with traditional approaches and has conducted a number of studies to better understand traffic and parking generation characteristics of the highly urban District. These methods, while significantly better than using national data, still lack sufficient sensitivity to the context of developments (that is, where it would be placed and what would surround it). This study applies the EPA MXD+ method to sites within The District. Based on those initial results, the EPA MXD+ method is then calibrated to better match District conditions. The resulting DDOT MXD+ method is then operationalized into an easy to use spreadsheet tool for use by DDOT staff in project development review.

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US Transportation Collection