What Happens When a Major Freeway is Closed for Repair?

Abstract

In the summer of 2008, a portion of Interstate 5 near downtown Sacramento, California, was closed in one direction at a time for reconstruction. The project, one of the first in California in which an entire direction of a major freeway was closed during commuting hours for planned repair work, lasted approximately 2 months and was expected to cause major congestion in the area (an area that in 2009 would be ranked in the top 49 most congested urban areas in the United States). This paper studies the actual traffic impact of the project and analyzes the behavioral and flow pattern changes that the project caused. Results showed that overall traffic demand on the freeway remained largely unchanged, with about a 3% to 7% reduction in daily traffic volume in the downtown area and less than 3% in the outskirt areas. The demand reduction during the commuting peak was more pronounced at about 7% to 12%, an indication of peak spreading. Rather than taking public transit, the majority of drivers who stayed away from the affected freeways during commuting hours chose arterial routes or earlier or later departure times. There is evidence that some drivers turned to carpooling in the initial stages of the project, but they reverted back to solo driving in the later stages. However, despite record high gas prices, vehicle volumes on the roadways returned to preconstruction levels 1 month after construction ended. This return to former volumes is an indication that people's travel habits are difficult to change in the short run.