A joint project between the Insurance Institute for Highway Safety (IIHS) and the Virginia Dept. of Transportation (VDOT) has found that simple traffic-management changes at heavily-traveled urban intersections – such as adding left-turn only lanes or reducing speed limits – reduced the number of vehicle crashes, and at a relatively low cost.

“Urban [roads] weren’t built to accommodate today’s heavy traffic. They’ve evolved as traffic has increased, and they haven’t always evolved in the best way to enhance safety and ensure a smooth flow of traffic,” said Richard Retting, IIHS’s senior transportation engineer. “So it’s a matter of studying urban arterials to pinpoint where crashes are occurring frequently and then identifying potential solutions, looking first for less costly measures that can be implemented more quickly than major re-engineering.”

About 8,000 deaths and more than one million injuries occur each year on urban roads, he explained, and these crashes aren’t occurring haphazardly. “Many of them happen in predictable locations and involve predictable sequences of contributing events. Remedies can involve costly and disruptive re-engineering of the roadways, but not always. Some relatively simple and inexpensive roadway changes can be effective,” said Retting.

Retting headed up the urban intersection project, which studied traffic on Leesburg Pike in suburban Fairfax County, VA. At two of the six locations studied, where crashes averaged 8.7 and 4.6 per year, protected left turn lanes reduced accidents to zero. At the other four, marked pavement with turn arrows cut annual crashes from 8.3 to just three, and extended merge lane reduced crashes from 8.2 to 0.9 per year, elimination of a bus stop dropped the yearly crash rate from 3.5 to 1.4, and widening a shoulder area for a bus stop cut annual crashes from 4.3 to 2.5.

“We applied some straightforward engineering improvements that were effective and not very costly,” said VDOT spokesperson Connie Sorrell. “Now we’re looking to use these and similar measures elsewhere.”