The Impacts of Road Capacity Removal

The road infrastructure of North America is aging, and many governments are faced with a critical decision: do we repair or remove freeways from our urban centers? Freeway repair is exceptionally expensive, but removing a freeway is widely seen as a risky venture which may result in negative traffic effects. Therefore, it is necessary to gain a clearer understanding of how removing road capacity effects traffic distribution. Three freeway segments were ultimately selected for case study analysis: two in San Francisco and one in Milwaukee. This analysis consisted of identifying changes in the traffic volumes and volume-capacity (V/C) ratios in freeways and streets in the areas surrounding the removed freeways. Overall, the results showed that when urban freeways are removed from the network, the traffic redistributes throughout the surrounding network. These case studies had significant excess capacity in the local street network, so the traffic was absorbed by the system without causing the V/C ratios to increase to a critical level. The pre-removal traffic distribution was distorted in the case studies, with high V/C ratios on freeways and low V/C ratios on streets. Removing the freeways caused a more balanced distribution in some cases; however the exact nature of the redistribution seems to depend upon the replacement boulevard design. These case studies were compared to nine other cities that are currently considering capacity removal projects. The distribution of traffic in these cities was also distorted, which indicates that excess capacity exists in these networks to absorb additional traffic volume