From marginalized to optimized : re-envisioning urban highway corridors

Abstract

The past century of highway construction has assumed relentless growth of vehicular traffic capacity. Yet today is an era of highway rationalization, aging facilities, strained finances, peak oil concerns, climate change, and urban regeneration. It is a prudent time to re-examine the place of highways within the urban fabric. The elevated structures associated with the urban highway model were for the most part constructed over 40 years ago and are nearing the end of their functional lives. This fact means that cities must decide whether to rebuild or redesign, and how. The increasing numbers of projects and multiple proposals for highway removal or shrinkage speak to a larger trend of right-sizing and quality of road design rather than a sole focus on throughput. This trajectory has been complimented by new and more context-appropriate guidelines for transportation planning and increased cross-pollination between urban planning and traffic engineering disciplines. This thesis finds that roadway capacity reduction is a successful traffic management strategy, with numbers from case studies in worldwide supporting the concept of traffic network flexibility and demand elasticity. This, in turn, may be able to better define how best to encourage mode shift from single occupancy vehicles to other modes. This thesis is an exploration of highway removal and redesign, and a proposal for context-sensitive transformation of the urban environment's lost spaces. It explores the underlying trends and methodologies of highway removal, examines several case studies, and then applies these findings to the case of McGrath/O'Brien highway in Massachusetts. This may serve as a precedent for future reexaminations of similarly degraded roadways and reveal implications for the future form of infrastrucure-burdened urban areas.