The Urban Freeway Gridlock Study investigated the effects of large trucks on peak-period urban freeway congestions. The study, undertaken for the California Department of Transportation at the direction of the California legislature was prompted by concerns about freeway congestion and proposals to regulate large-truck traffic on the freeways. The study focused on the freeway systems in the Los Angeles, San Francisco, and San Diego metropolitan areas. It addressed the effects of large trucks, strategies to reduce congestion (improved traffic management, expanded incident management, mandatory night shipping and receiving, and mandatory peak-period truck bans), and the economic effects of these strategies. It was concluded that the volume of large trucks on the freeways does not have a significant effect on peak-period congestion but that truck-involved incidents and accidents do affect congestion significantly. Truck traffic makes a relatively small contribution to freeway congestion except on those few highly congested freeways where truck volumes exceed 10% of total vehicles. It was recommended that the state expand and improve its incident management programs and concurrently expand and intensify its long-term traffic management programs. The state should support a pilot program in Los Angeles to determine whether a cost-effective night shipping and receiving program can be developed. Areawide freeway truck bans should not be pursued; however, time-of-day and lane restrictions should be researched. Finally, it was recommended that the state collect data and improve traffic modeling procedures used to estimate the effects of trucks on air quality.
Abstract