Effects of vehicle restriction policies: Analysis using license plate recognition data in Langfang, China

To mitigate externalities of the urban transportation system, various travel demand management policies have been tested across the world in the past decades. Among them, vehicle restriction is considered the most straightforward way to reduce travel demands. The effects of this policy, however, are still inconclusive. Using the massive license plate recognition (LPR) data in Langfang, China, this study investigates the differences of two typical license-plate-number-based vehicle restriction strategies, i.e., One-Day-Per-Week (ODPW) and Odd-And-Even (OAE). This study compares ODPW and OAE from two perspectives: travel demand and traffic condition over the road network. In addition to the change of traffic volume, the analysis of travel demand also includes the investigations of “illegal” travel, which denotes the road use of restricted vehicles, and travel intensity, which represents the travel frequency of certain vehicles in a time period. The changes of traffic condition are assessed by travel speed. Findings confirm that traffic volume declines as ODPW shifts to OAE, but not as significantly as expected. This less-than-full adjustment can be explained by the increase of illegal travel and travel intensity. The policy shift from ODPW to OAE significantly improves the travel speed in most of the road segments, whether in peak hours or off-peak hours. The conclusions in this study provide in-depth insights into the influence of vehicle restriction policies and contribute to the effective design of travel demand management strategies.