Driven by problems of traffic congestion, U.S. policy toward urban highways has lurched over several decades from highway building to high-occupancy-vehicle lanes to travel demand management. Yet congestion has worsened, and there is scant evidence that these policies have had any appreciable...

Everyone knows that being stuck in traffic is stressful, and few look forward to long commutes on congested roadways. But the negative effects of traffic congestion go beyond frustration and fatigue. Our research at UC Irvine since the late 1970s has discovered adverse health impacts of what we...