Arlington County, Virginia has requirements for many proposed development projects that allow county transportation experts to measure key indicators such as parking occupancy, vehicles moving in and out of garages, and commute mode choice of residents.
Individually, these studies can be used by these experts to compare reality against the projections used in the traffic-impact analysis prior to project approval. Building-specific results also can be used to work with building owners and property managers to offer more and better transportation options to reduce traffic impacts and increase quality of life for residents, workers, and visitors to the county.
But this work is not just about Arlington. These studies also allow us to feed current, detailed, local data back to national organizations such as the Institute of Transportation Engineers (ITE), a cornerstone of transportation planning and infrastructure design throughout the nation. For a great synopsis of the work they do, check out their blog post. By giving our data to ITE for inclusion in the refinement of their trip and parking-generation guides, we are changing the baseline against which development proposals across the country are compared.
Analyzed cumulatively, our performance monitoring studies begin to tell a story about the transportation impacts of development in Arlington’s Metrorail corridors, urban villages, and across the county as a whole. Through them, we see that development in Arlington is in some ways very different from the development that has historically contributed to national trip-generation factors and estimates.
The county’s new transportation study of 16 residential buildings in Arlington observes vehicle trip generation during morning and evening peak hours on weekdays, daily peak hour on weekends, and total daily vehicle trips on all days of the week being much lower than predicted based on appropriate ITE rates for buildings within the Metrorail corridors. (Observed vehicle-trip-generation rates for buildings outside the Metrorail corridors were also lower than applicable ITE rates.)
This aggregate study offers several insights for local planners, developers, and community members about trips being made to buildings within the Metrorail corridors:
- Residents in these buildings are taking far fewer vehicle trips per dwelling unit than predicted by national standard rates.
- Residents in these buildings drive alone for their commutes less often and use transit more than all Arlington residents and the region.
- Living close to Metrorail is related to lower vehicle trip generation and drive-alone commute share. The latter is further reduced if residents also work in a very transit-walk-bike-accessible place, such as Arlington or Washington D.C.
- Few garages even approached “full,” and many cars parked in them are rarely used.
- As work parking price goes up, drive-alone commuting goes down. And as home parking price goes up, vehicle ownership goes down.
- Higher workplace transportation demand management (TDM) is associated with higher use of non-drive alone modes for commuting.
- Use of non-drive-alone modes is higher for commute and non-work trips when respondents know of Arlington services, higher still if they have used the services.
Arlington’s data are helping national organizations such as ITE better reflect the operation of buildings in situations that are mixed use, higher density, transit-oriented, and employ various TDM practices. And our data documents lower vehicle-trip-generation rates than planners and policy makers have previously expected based on national estimates.
Having standards that do not over-estimate traffic and parking demand can help create better planning policies and help developers create living and working places that maximize space for the fun stuff – where we eat, sleep, work, play, talk, shop, walk, bike, browse, lounge – instead of maximizing space for cars.
Communities are not static, but rather ever-changing, and Arlington is no exception. It follows that a commitment to ongoing observation, measurement, discussion, and reflection is necessary to ensure that new development and the accompanying transportation system and services continue to meet the needs of current and future generations.
Photo by Elvert Barnes