University of California Transportation Center

Large scale suburbanization of employment has dramatically changed transportation and land use planning. Intersuburban commuting now dominates regional highway networks, and the automobile has replaced mass transit for many commutes. Planners' approaches to these developments vary from the pro-centralization approach of many environmentalists and transit advocates to the view that employment suburbanization enhances mobility. In the middle are those planners who seek a geographic match between suburban jobs and suburban housing. This study examines one aspect of the debate on the effects of employment decentralization on regional mobility: the impact of growing suburban employment on the commutes of different income groups. This study suggests that suburban employment centers with high levels of multifamily housing will exhibit commute patterns in which household income and commute distance are largely independent. In contrast, In suburban areas where the development of dense housing has not kept pace with employment growth, it is hypothesized that new commute patterns are emerging wherein lower income households commute greater distances than their upper income counterparts. This pattern would be the reverse of the prediction of monocentric urban models for central city employment. These hypotheses are tested for San Francisco Bay Area communities using data from 1981 and 1989. Bivariate analyses generally supported the predicted effects of community employment base and housing stock on commute patterns by income. Nested multinomial logit models of the household residential location decision were estimated for workers in San Ramon and in northern Santa Clara County. The models appeared to demonstrate a positive effect of the availability of multifamily housing on the residential location decisions of low to moderate income households. In addition, workplace accessibility in general emerged as a powerful determinant of residential location. Forecasts of commute patterns using the estimated models indicated a potential for reducing long distance commutes by low to moderate income households through a policy encouraging multifamily housing construction in the vicinity of suburban employment centers.