Adam Millard-Ball

This policy paper focuses on the primary concept of the street as space that can be repurposed – real estate that can be allocated in similar or different ways than done currently. Cities generally refer to this publicly owned and regulated space from one side of the street to the other as the right of way (ROW). Our focus is on the centrality of the ROW in dictating many other community functions and values – transportation and otherwise. And our particular bias is to focus on the opportunities that AV technology is likely to create to rethink how the ROW is allocated, so that our communities can meet their substantial and unique environmental, social, and economic challenges.

We quantify the importance of early action to tackle urban sprawl. We focus on the long-term nature of infrastructure decisions, specifically local roadways, which can lock in greenhouse gas emissions for decades to come. The location and interconnectedness of local roadways form a near permanent backbone for the future layout of land parcels, buildings, and transportation options. We provide new estimates of the environmental impact of low-connectivity roads, characterized by cul-de-sacs and T-intersections, which we dub street-network sprawl. We find an elasticity of vehicle ownership with respect to street connectivity of –0.15—larger than suggested by previous research. We then apply this estimate to quantify the long-term emissions implications of alternative scenarios for street-network sprawl. On current trends alone, we project vehicle travel and emissions to fall by ∼3.2% over the 2015–2050 period, compared to a scenario where sprawl plateaus at its 1994 peak. Concerted policy efforts to increase street connectivity could more than triple these reductions to ∼8.8% by 2050. Longer-term reductions over the 2050–2100 period are more speculative, but could be more than 50% greater than those achieved by 2050. The longer the timescale over which mitigation efforts are considered, the more important it becomes to address the physical form of the built environment.

TCRP Report 108 presents the research team’s findings on the: Current and potential roles of car-sharing in enhancing mobility as part of the transportation system; Characteristics of car-sharing members and neighborhoods where car-sharing has been established; Environmental, economic, and social impacts of car-sharing; Ways in which partner organizations have tried to promote car-sharing; Barriers to car-sharing and ways to mitigate these barriers; and Procurement methods and evaluation techniques for achieving car-sharing goals.