Reconnecting America People * Places * Possibility

TOD, Aging And Networks And Their Impact On Transit

Three research papers examining various aspects of ridership added to Best Practices

The effects of transit-oriented development on housing, parking and travel; the potential for the graying of America to increase transit ridership; and an article that empirically tests for positive network effects in transit use have been added to the Best Practices.

Effects of TOD on Housing, Parking, and Travel (2008)

The objectives of this research by GB Arrington, Robert Cervero and others on behalf of the Transit Cooperative Research Program are to determine the behavior and motivation of TOD residents, employees, and employers in their mode choice; identify best practices to promote TOD-related transit ridership; and recommend contextual use of best practices.

This research helps confirm what had been intuitively obvious: in the four metropolitan areas studied, TOD housing produced considerably less traffic than conventional development. Yet, as the researchers found, most TODs are required to have parking based on the assumption that there is little difference. One likely result of this fallacious assumption is that fewer TOD projects get built. As a result, many of the hoped for benefits (i.e., less time stuck in traffic and lower housing costs to name two), from the nearly $75 billion in public dollars invested in rail transit over the past 11 years, are not being realized, according to the report. The researchers anticipate that right-sizing parking ratios and traffic generation to the actual performance of TOD would result in some important implications on the physical form and performance of TOD developments. Developing residential TODs based on an accurate assessment of their traffic impacts, the researchers concluded, should result easier development approvals, better planned and more compact communities, increased transit ridership, and more affordable housing.

Estimating the Impacts of the Aging Population on Transit Ridership (2006)

This report, which was written by ICF Consulting on behalf of the National Cooperative Highway Research Program, outlines the key demographic factors that affect public transportation use with a particular focus on how the aging demographics of the country will impact future transit ridership. In addition, the report describes a spreadsheet tool that can be used to estimate the future effects of the aging population on public transportation use. This report also explores specific mobility problems, examining predictors of staying home on a given day, and travel for non-institutionalized people with medical disabilities. The report is intended primarily for the use of public transportation agencies. The ridership model developed under this project provides a way for public transportation agencies to estimate the effect that the aging population in their service area will have on overall ridership and costs.

Network Effects in Public Transit Use: Evidence from a Spatially Autoregressive Mode Choice Model for New York (2008)

Frank Goetzke's article empirically tests for positive network effects in transit use. Positive network effects exist when people prefer to use transit together with other people as a result of social spill-over. The article tests for these effects using a spatial autoregressive logit mode choice model with 1997/98 work trip data from New York City. Although these network preferences should differ for each person, it is possible to derive econometrically a measure of aggregate network preference.

Goetzke's papers offers insights into ridership estimates and why they turn out to miss the target. "[A]s long as the relative utility for using transit in the suburbs is lower than average and, in the central city, higher than average, transit ridership will be overestimated in the suburbs and underestimated in the central city. ... This new insight might at least partially explain why new rail starts in the past decade have had problems with inflated ridership forecasts compared with the observed ridership after opening."