Do public transit and agglomeration economies collectively enhance low-skilled job accessibility in Portland, OR?

Abstract

Research related to the spatial mismatch hypothesis has demonstrated that the decentralization of jobs undermines job accessibility for socially and economically disadvantaged groups, especially those dependent on public transit. One potential solution is the promotion of agglomeration economies associated with transit infrastructure which could enhance job accessibility for low-wage or low-skilled workers by centralizing jobs to urban areas with relatively high-density surrounding transit stations. However, the dramatic change in spatial distribution of low-skilled or low-wage workers through Transit-Oriented Development (TOD) could limit jobs available to the underrepresented workers in the urban central area. In this case, agglomeration may not help these workers have better access to matching jobs. To unravel these relationships, this research investigates the effect of agglomeration related to transit's positive externalities on gravity-based job accessibility by transit in Portland, OR. Furthermore, this study compares the agglomeration impact on low-skilled job accessibility to the overall job accessibility. Effective job density is proxy for transit-related agglomeration economies in the analysis. The relationship is estimated with spatial econometric models to evaluate the direct effect as well as the spillover effect of agglomeration. Overall, the agglomeration with benefits from transit network and service brings a positive effect on job accessibility. However, agglomeration economies of one location reduces the job accessibility of their neighbors, implying that concentrating economic activities beyond a certain spatial scale may absorb jobs from the neighboring areas. Policymakers and urban planners should set an upper limit in the spatial scale of TODs to avoid a zero-sum game. The agglomeration effect on job accessibility for low-skilled workers is not as strong as the accessibility for all workers, calling for decision-makers’ attention to the importance of “redistributing” the agglomeration effect through progressive land use and transportation policy efforts for underrepresented workers.