A new report released by AAA explored how various road infrastructure improvements could reduce the number of crashes as well as the severity injuries that result from those crashes. The report examined 12 types of improvements, including converting certain stop-controlled and signal-controlled intersections into roundabouts. The United States nearly last among high-income nations in terms of annual traffic fatalities, causing more people to consider these changes. The report states that “France has built over 20,000 roundabouts in the last 15 years as a key safety improvement to their road system.”
Roundabouts are safer than transitional four-way intersections for a number of reasons. First, due to the simplicity of roundabouts, there are fewer points for “conflicts,” which are essentially combinations for how cars could collide with each other. Second, collisions that do occur at roundabouts tends to happen at acute angles, minimizing the severity of the impact, whereas collisions at traditional intersections are often at 90-degree, T-bone angles. Third, vehicles travel at slower speeds through the roundabout. All of this adds up to big safety gains.
Converting a stop-controlled intersection could reduce injury crashes by 82 percent, and converting signal-controlled intersections could reduce injury crashes by 78 percent. Intersection improvements in general, including roundabout upgrades, would save nearly 20,000 lives and prevent more than 105,000 serious injuries over the course of 20 years, with roundabouts being the most effective of intersection improvements, making it the most beneficial and effective of all of the infrastructure improvements explored in the AAA report.
The AAA estimates the cost of converting an urban intersection into a roundabout at around $2.5 Million, and also estimates a 20-year service life for such a project.
The report also looked at widening lanes, widening and paving shoulders, dividing roadways with medians, adding passing lanes, adding rumble strips to roadway edges, adding turning lanes at intersections, improving signal timing, and improving pedestrian and bicycle infrastructures. These improvements were chosen for their relatively low cost as compared with the high return on safety improvements. Over a 20-year period, nearly 64,000 lives could be saved, and more than 350,000 serious injuries could be prevented.