A higher proportion of trips made in high-occupancy vehicles, or by walking or bicycling, or avoided altogether during the morning commute means reduced delay for everyone traveling on the system.

The Washington State Legislature passed the Commute Trip Reduction (CTR) Law in 1991, incorporating it into the Washington Clean Air Act. The goals of the program are to reduce traffic congestion, reduce air pollution, and petroleum consumption through employer-based programs that decrease the number of commute trips made by people driving alone.