Results:

• This study defines a framework of “5 D’s” used in transportation research literature, which classifies changes in the built environment that can influence travel choices using the following categories:
  • Density: measures a variable of interest per unit area (e.g. household/population density and job density)
  • Diversity: measures the mix of land uses in an area (e.g. land use mix and jobs-housing balance)
  • Design: measures street network characteristics (e.g., intersection/street density and percent of 4-way intersections)
  • Destination accessibility: measures ease of access to trip destinations (e.g., job accessibility by auto or transit; distance to downtown)
  • Distance to transit: measures street routes from home or work to the nearest rail or bus stop (e.g., distance to nearest transit stop)
  • Overall, the relationship between individual built environment variables and travel choices was relatively inelastic (no more than 0.39, meaning that a 10% in a factor of the built environment only changes travel choices by 3.9%), but combining multiple built environment changes could have a greater effect.
  • Measures of destination accessibility was most strongly associated with both motorized and nonmotorized travel, and population and job densities had the weakest association with travel choices.
  • Walking was most strongly related to land use diversity, intersection density, and destinations within walking distance.

Methods:

• This meta-analysis synthesizes effects of the built environment on travel choices from 50 research studies. To create a common metric to compare outcomes across studies, the researchers calculated elasticities, which represent the percent change in choosing a travel mode relative to a 1% change in a specific aspect of the built environment.

Ewing, R., and Cervero, R. (2010). Travel and the Built Environment. Journal of the American Planning Association, 76(3).