As new development places increasing demands on the transportation system, community leaders, land-use planners, developers, and transportation agency administrators need techniques to enable them to reliably predict the number of net vehicle and person trips that will be generated by new or infill mixed-use development.
For site impact analysis purposes, an internal capture rate that is set too low may unfairly penalize developers by making them pay more than their fair share of costs for transportation mitigation measures. Conversely, an internal capture rate that is set too high may unfairly place this burden on the public. Both cases may result in sub-optimal build-out, particularly in urban areas.
Since the internal capture rate used for a given mixed-use development can be politically contentious, empirical observations are needed to provide professional guidance for better estimating these impacts. By improving the methods for estimating internal capture, the process of determining developers' responsibilities for mitigating transportation impacts of mixed-use development will become more equitable, transparent, and open.
The objective of this two-phase project was to produce a methodology for enhancing internal trip capture estimates that includes (1) a classification system of mixed-use developments that identifies the site characteristics, features, and context that are likely to influence internally captured trips and (2) a data-collection framework for quantifying the magnitude of internal travel to and around mixed-use developments to determine the appropriate reduction rates.
The final report has been published as NCHRP Report 684. An unlocked version of the spreadsheet model is available here.