UPDATED ABSTRACT: Recent California policy discussions suggest that the travel impacts resulting from strategies for housing growth are not well understood, in part because metropolitan growth has always occurred according to local zoning and land use plans. Fundamental alterations of local planning guidelines, in turn, have unknown transportation impacts. This project reviewed and synthesized policy and academic literature on housing-and-transportation linkages. The project team then applied a process developed in related research to categorize tour-based travel patterns and related these to household characteristics. The project team established connections between household tour behavior and residential variables, which were used to classify types of travelers. The focus of this research was on users of public transit and ride hailing services.

This project will synthesize two sets of studies concerning the causes and consequences of local growth control focusing on implications for transportation and the unique context of each study. The first set of studies addresses the determinants of local growth controls and the circumstances under which a locality is likely to adopt relatively restrictive land use regulations. This body of work includes municipality-level analyses of the determinants of growth control and investigations of voting patterns on growth control measures and relevant issues. The second body of research to be reviewed is related to how limited housing supply (due to growth control and/or other regulatory barriers) affects household residential location and travel patterns. This body of work covers empirical research on the impact of inelastic housing supply on population distribution and resultant transportation outcomes as well as studies on broader transportation challenges that arise due to regulatory barriers to housing development and forces behind them.

Concerns about the environmental impacts of transportation have turned reducing vehicle-miles traveled (VMT) into a policy priority. One way to decrease VMT is to reduce the length of commuting trips. Unfortunately, the average U.S. commute keeps getting longer. Prior research has investigated the determinants of commuting, but few have analyzed the linkage between housing costs and the length of commuting. This problem is especially salient in California given the state’s perennial housing shortage and the high costs of housing, which have forced many lower- and middle-class households to move inland in search of more affordable housing at the cost of longer commutes. Most of those commuting trips are by car. This project investigates these linkages using Generalized Structural Equation Modeling and analyzing 2012 CHTS data for Los Angeles County – the most populous county in the U.S. The model, which jointly explains commuting distance and time, accounts for residential self-selection and car use endogeneity, while controlling for household characteristics and land use around residences and workplaces. Better understanding the determinants of commuting is critical to inform housing and transportation policy, improve the health of commuters, reduce air pollution, and achieve climate goals.

California’s Housing Element law requires the allocation of housing targets to local governments. These targets should align with long-range regional strategies to concentrate growth in transit rich areas, but little evidence exists about the effectiveness of housing allocation schemes for achieving accessibility and affordability. Indeed, there is some evidence that – to date – the law has not served these goals effectively. In 2018 California Senate Bill (SB) 828 significantly amended the Housing Element law, conferring additional authority on the California Department of Housing & Community Development (HCD) to determine housing targets. Moreover, SB 50 (introduced in 2019) proposes to require HCD to identify “jobs-rich” areas, in which local governments would be required to allow relatively dense residential development. SB 50 proposes to also raise the minimum allowable density for residential development in areas close to transit stops. State legislators and administrators have very little information to evaluate the current housing target allocation process or its interaction with the regulatory scheme contemplated by SB 50. This project would fill that gap, providing guidance for linking housing and transportation policy. This project will provide decision support for state legislators and administrators by: 1) comparing California’s housing target allocation and implementation methods to methods currently used in other states, as well as methods described in the scholarly literature; 2) comparing the possible effects of different allocation and implementation methods on job accessibility at different levels of housing affordability; and 3) identifying ways that future legislation and implementation could promote the goals of the Housing Element law related to accessibility.