Methodology for Determining the Economic Development Impacts of Transit Projects. TCRP Web-Only Document 56.

摘要

The report was aimed at developing a method for transit agencies to assess whether and under what circumstances transit investments have economic benefits that are in addition to land development stimulated by travel time savings. The method was intended for possible use by transit agencies proposing new transit systems as well as major capital investments in existing transit systems. Current evaluation procedures include estimates of travel time savings, costs of construction, environmental impacts, and effects on land development. This TCRP study addresses an additional type of impact: the productivity increases associated with agglomeration economieseconomies of scale in densitythat may be caused by transit improvements. We reviewed existing evaluation practices and academic research, and then carried out a wideranging empirical study on metropolitan-level data from cities across the US, firm-level data from two metropolitan areas, and case studies of three recent transit projects. A study of this question had never been carried out in the US to our knowledge. Recent research in the UK has been the basis for the formal evaluation of such impacts there and has suggested that agglomeration-related benefits are substantial. The measures of agglomeration used for the empirical estimates in this report are at the metropolitan area level: employment density in the urbanized area and the principal cities of the metropolitan area, and the size of the metropolitan area as measured by its population. While we investigate local level measures of density in our firm-level analysis, we are unable with the available data to investigate how clustering of activities in certain economic sectors in close proximity to one another or to other businesses such as business services or suppliers, within a defined radius of transit stations, might affect productivity. However, we find evidence that there is little such activity occurring in the two regions for which we have firm-level data, or for the three case study regions. This report does not address the development impacts of opening new transit lines or transit stations. Although such transit-induced development may have local benefits, this type of impact is already addressed in current guidance. From a regional or national perspective such development impacts may be primarily redistributive rather than a net addition to economic growth, and therefore there is reason to discount them as additive effects.