Agglomeration benets and transportation projects:a review of theory, measurement, and application

摘要

Traditional project appraisal assesses benets from a number of sourcesincluding improvements in safety and reductions in noise levels, travelcost, and travel time. In most cases benets are primarily based on traveltime savings. Project appraisal based primarily on travel time savings sys-tematically underestimates the benets of projects that create economicbenets beyond travel time savings and thereby introduces systematicbias against investment in an important subset of initiatives particularlyin the case of projects large enough to alter the time-space geographyof a metropolitan area. Recent research has developed methodologies tocapture some of these previously unaccounted-for benets of transporta-tion projects, most notably agglomeration benets. London's $25 billionCrossrail project broke new ground by incorporating agglomeration ben-ets in the project appraisal process which it estimated added 24% tothe project's benets on top of conventionally appraised benets. Whilemethodologies now exist to measure agglomeration benets, their inclu-sion in project appraisal is limited, partly because agglomeration and itssources are not well understood. This work seeks to explain agglomera-tion in an understandable manner through a review of previous researchon the sources of transportation benets and appraisal methodologies.This study also reviews the agglomeration calculations of a number ofprojects and specically highlights projects in London, Melbourne, andTel Aviv.