TripsDC
TripsDC is a tool to estimate trip generation for mixed-use developments (residential and retail uses) within the District of Columbia.
TripsDC is a tool to estimate trip generation for mixed-use developments (residential and retail uses) within the District of Columbia.
This tool estimates vehicle, walk, bike, and transit trips based on a proposed development's characteristics and its context. Here you can explore the context inputs for the model and the mode shares for a typical development in the District.
This tool estimates multimodal trip generation for any address in the District.
Trip generation means the number of trips by transportation mode expected to be created by a development project. Trip generation estimates are the first step in transportation impact analyses for development projects. Trip generation models provide estimates of the number of trips, by mode, produced or attracted to a given land use or activity as a function of the demographic, socioeconomic, locational, and land use characteristics of the zone. These trips are then used to determine a project’s “impact” on the transportation network. Based on the “impact” estimated, changes in the transportation network may be proposed (e.g. proposed project with high bicycle activity may encourage building more bicycle infrastructure).
DDOT works through the Development Review process to assess a project’s impacts and determine appropriate mitigations. Better trip generation estimation is important for identifying likely project impacts and identifying appropriate mitigations.
A locally calibrated and validated trip generation tool based on data from more than 50 residential over retail developments within the District. The tool is preloaded with variables to apply the model at any address within the District and estimate trips by auto, walk, bike, and transit.
This tool is most effective for residential-over-retail developments on sites between 0.5 and 5 acres with up to 750 residential units and up to 75,000 square feet of retail.
Data was collected at 55 sites which were predominantly residential-over-retail. The statistical model is representative of the built environment associated with these sites. Note that the land uses were limited to multi-family apartments and neighborhood retail, and did not contain unique residential or retail land uses. As a result, projects which propose land uses outside of this context should consider additional adjustments. While residential-only development are an acceptable application of the tool, retail-only developments are not recommended as the statistical analysis did not include this type of land use. For sites which propose zero parking supply, the tool can be used with consideration for manual adjustments, given how the statistical analysis included limited examples of this.
By far, the most common trip generation method used in the industry is ITE’s Trip Generation Manual, which estimates vehicle trips based on a single independent variable, such as dwelling units, thousand square feet (KSF), acres, or employees. This method simplifies the process of estimating trip generation at the cost of flexibility and accuracy. ITE’s Trip Generation Manual does not estimate trip generation by purpose or by mode other than vehicle.
There is a widespread belief that the available tools for estimating travel impacts of urban development are not as strong as they could be. Implications include:
Most transportation impact analyses in the USA rely on the ITE Trip Generation Manual. The benefits of using ITE as a trip generation basis include a large established database of rates by land use, widespread industry acceptance, and relative ease of use. The disadvantages include sacrificing local context for national breadth of data. The trip generation data included is largely representative of individual, single-use suburban developments whose trips are made by private vehicles. Even before analyzing complex urban and mixed-use developments, ITE has been shown to be less reliable for evaluating simple single-use developments. In particular, the small sample sizes used to derive rates, and the wide range of values present in the data set, indicate that there are factors missing.
TripsDC is the result of a four year research effort by the District Department of Transportation’s (DDOT) to (1) develop and test a data collection methodology, (2) collect local data to substitute for Institute of Transportation Engineers’ (ITE’s) national data in trip rates estimation, and (3) develop a model/tool that incorporates factors identified affecting overall trip rate as well as trip rate by mode. The model makes two major steps forward: directly estimating total person trips, and being sensitive to the amount of parking provided on site – a major finding in the connection between parking provision and travel behavior at a local site level. The methodology allows DDOT to improve its assessment of expected trips from proposed buildings and therefore the level of impact a proposed development might have on the transportation network.