University of California Transportation Center

Regulation XV of the South Coast Air Quality Management District in Southern California requires all work sites at which there are 100 or more employees to implement a ridesharing program by which the organization's "average vehicle ridership" is intended to be increased to a specified target level. This paper summarizes the requirements and procedures required by the regulation. It also presents the first evaluation of the results of this far-reaching program after more than one year of experience. The preliminary evaluation is based on a small number of observations comprising a sample of employment sites which is less than fully representative of all sites affected by the regulation. The early results are encouraging, and show that there has been a small but significant increase in average vehicle ridership, and a corresponding decrease in commuting by single-occupant automobile. Most of the change is found to be the result of increased carpooling, while the use of compressed work hours and walking and bicycling also increased. The research reported here is ongoing and will in time should yield more definitive results.