Searching for induced travel: Elimination of a freeway bottleneck and subsequent effects on rail and freeway volumes

The removal of a freeway bottleneck in California has allowed researchers to investigate short-term induced travel and a potential mode switch from rail transit. This particular bottleneck, a double lane drop from reduced tunnel capacity, is a unique case as alternate auto routes are quite undesirable; the only other option is to consider nearby rail transit. Freeway volumes and rail ridership were examined before and after the removal of the bottleneck to estimate the extent of induced travel. Freeway volumes during both commute periods increased 10-13%, faster than other nearby locations, and rail transit ridership between stations on either side of the pre-existing bottleneck showed modest declines despite system wide increases. Differences of means testing confirmed that many of these changes were statistically significant. Examining the magnitude of induced travel is relevant when making policy decisions for removing mature bottlenecks that involve the use of public finances.