3. Density, Transit and Vehicle Ownership
This section is intended to address two questions about vehicle ownership and
thus demand for parking at housing developments:
Do households in higher density areas have lower rates of vehicle
ownership, keeping other factors equal, like income?
Do households living in neighborhoods with better transit service have
lower rates of vehicle ownership, again, other things equal?
Unfortunately, this is not an issue in which simple data can help answer the
question. However, this issue has been studied somewhat, and generally the
answer is yes to both questions.
The impact has been best incorporated by the research for the Location
Efficient Mortgage. Density, transit and demographic factors interact to
impact vehicle ownership. The interaction has been modeled and can be used
by planners and developers to help predict likely vehicle ownership (and
vehicle miles traveled) of future residents of a development. This tool is
explained and available in the Model section of this website.
Unfortunately not many studies have looked closely at neighborhood
characteristics and vehicle ownership. Three of the most relevant studies
are summarized below:
| Places Studied |
Study Description |
Finding |
Source |
| 27 California Neighborhoods
(from San Francisco, Los Angeles, San Diego, and Sacramento Regions) |
Compared density, transit
service, neighborhood shopping, and pedestrian accessibility with auto
ownership and vehicle miles traveled. Demographic characteristics
were somewhat controlled for by selecting communities with similar
incomes. |
Auto ownership declined in each
region as density of each neighborhood increased. Doubling density
resulted in a 16% reduction in vehicle ownership per household.
There was not enough data to detect whether transit service, neighborhood
shopping, and pedestrian accessibility had an impact on vehicle ownership
independent from density. |
Holtzclaw |
| Nationally by Zipcode |
Modeled vehicle ownership,
vehicle trips, and vehicle miles traveled with zipcode densities, incomes,
transit service and demographic factors using NPTS data. |
For
each 1 percent increase in density (about 2/3 of a unit per acre), vehicle
ownership fell by 0.11 vehicles per household. |
Schimek |
| Bay Area (1,000 traffic analysis
zones and 1,200 Census tracts) |
Combined
land use data and Bay Area travel survey data to explore impacts of mixed
use, land use balance, and density on travel behavior controlling for
income and demographic factors. |
-Auto
ownership is lower in areas with mixed-use, near jobs, and higher density.
-Auto
ownership is more significantly influenced by local attributes of the
build environment (density and land use balance) than VMT and mode choice. |
Kockelman |
Sources:
Holtzclaw, John. 1994. Using Residential Patterns and Transit to Decrease
Auto Dependence and Costs. San Francisco: Natural Resources Defense Council.
Schimek, Paul. 1996. Household Motor Vehicle Ownership and Use: How Much Does
Residential Density Matter? Washington DC: National Research Council,
Transportation Research Board.
Kockelman, Kara M. 1997. Travel Behavior as a Function of Accessibility, Land
Use Mixing and Land Use Balance: Evidence From the San Francisco Bay Area.
Washington, D.C.: National Research Council, Transportation Research Board.
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