University of California Transportation Center

High occupancy vehicle (HOV) lanes are being promoted as a way to reduce congestion and air pollution on urban freeways. While constructing new general purpose lanes is often seen as environmentally destructive, constructing new HOV lanes is seen as good for the environment and effective in reducing congestion. The reality, however, is that although both are effective in reducing emissions and congestion, construction of a general purpose lane will be more effective in a wide range of typical conditions.