Impact of new highways on road deaths: a case study in risk assessment

Epidemiologists have generally avoided to assess risk for road deaths from high-speed highways. We examined the validity of the claim that the Trans-Israel Highway, a six-lane 320 km toll road with higher design speed, and raised speed limits (120 kph), will reduce road deaths. We used models showing that death tolls vary with the fourth power of rise in driving speed. Risk assessments was derived from estimates of increase in the highway-induced traffic, the impact of higher speed limits (from 110 to 120 kph) and the so-called spillover effect from speed habituation. We predict a large rise in the number of killed or injured, even if the death risks per vkm is low on the Highway itself. With the Trans-Israel Highway, death tolls--some 550 fatalities per year in 1995, could rise to as high as 900-1000 per year in 2010. Congestion produced by induced traffic will partially offset these effects. By contrast, death tolls from alternative strategies based on sustainable transportation policies could be reduced to less than 300 deaths per year. Risk assessment based on explicitly defined assumptions predicts high death tolls from the nationwide impact of raised speed on the Highway and its connecting roads. There is a need for new frameworks which impose the Code of Helsinki type requirements for the assessment and authorization of social decisions with adverse public health impacts.