Without a major shift in public attitudes toward using public transportation and driving less, there are limits to how far new public transportation systems and transit-oriented development can go in reducing traffic flow on local streets and highways, according to new research by economists at NAHB.
Relatively few home buyers and renters choose a neighborhood because of its proximity to public transportation, the study found.
Based on data from the Department of Housing and Urban Development and the U.S. Census Bureau, the NAHB study on “Household Type, Housing Choice and Commuting Behavior” found that relatively few married couples with children consider public transportation when selecting a neighborhood, and that they are likely to own more cars and travel more miles to work than other types of households.
Married couples, the research showed, are more likely to settle in a particular neighborhood because they like its appearance or it’s the location of a home they particularly like. One-person households, on the other hand, care about finding a location near where they work more than anything else.
Economists at NAHB note that these results have implications for land use planning — suggesting, for example, that different types of housing are needed to serve different types of households, and that the appropriate mix of housing in a transit-oriented development may differ from the mix needed to serve the local labor market as a whole.
The Size of City Blocks
Focusing on another aspect of the built environment, the study investigated the relationship between commuting patterns and the size of city blocks.
In the absence of other types of consistently complied data, block size is routinely used by academic researchers to measure street accessibility and interconnectivity.
Tracts with the smallest blocks — and therefore, at least theoretically, the best connected and most accessible streets — have the highest percentage of people walking and bicycling to work, according to the research. However, under the best of circumstances, cyclists and walkers never exceed 10% of the commuting population.
Smaller blocks also lead to shorter commuting times, the data suggested; at least until the average block size falls to 50,000 square feet. When blocks are smaller than that, the trend is reversed and commuting time starts to increase.
The study concluded that commuting times are longest in tracts with an average block size of under 20,000 square feet, indicating that there are limits on how small it would be desirable to make blocks in new residential developments.