Reuters

Efforts to fight congestion by centralizing traffic lights could also make roads more dangerous for walkers

Sally Flocks is on a mission to slow drivers down.

Flocks is the president of PEDS, an Atlanta-based pedestrian rights organization. And she says one of the best ways to protect walkers is to keep drivers cruising at about 20 mph when they're in cities. Walkers are significantly more likely to survive an accident with a car at that speed. The odds of dying increase dramatically if a driver is speeding along at 30 or 40 mph.

Flocks has lobbied for a wide variety of changes to make her goal a reality. She's a big fan of HAWK signals, pedestrian-activated crossing signs that force drivers to stop when someone needs to cross the road on foot. On her wish list for Atlanta are wider curbs that require drivers to slow when they turn.

And there is her recent victory. PEDS convinced Atlanta officials to install signs telling drivers that the law requires them to stop for pedestrians at crosswalks. The first signs went in at the very intersection where Gone With The Wind author Margaret Mitchell was killed. It was so effective that similar boards have been installed around the city.

But slowing drivers can sometimes impact another city goal: fighting congestion. In Minneapolis, the city is installing an innovative system, that will, officials hope, cut down on commute times. According to the 2011 Urban Mobility Report, the Twin Cities' residents waste about 45 hours a year in traffic.

Officals are hoping to change this with a new system that will coordinate traffic lights. The plan includes a "sweeping new timing system" for intersections throughout the city. On key commuter roads, drivers will now likely get through ten lights rather than just two or three. And a centralized system includes actuated signals, which can "detect waiting traffic, and change their timing patterns accordingly."

But David Goldberg of Transportation for America says timed signals can be dangerous if they encourage drivers to speed through lights, and force pedestrians to wait too long for an opportunity to cross. He, like Flocks, is an advocate of systems like HAWK, which empower pedestrians to cross safely.

Flocks says timed lights can work if they're used correctly. She warns against systems that encourage drivers to speed up to get through as many lights as they can.

But some lights are designed to incentivize the opposite, she says. The key is the timing. If traffic lights are designed so that you have to speed a little to get through them all, then that's what drivers will do. But some cities have a system in place that punishes speeding drivers. Drivers going five to ten miles over the speed limit are stopped every third light. If you're going exactly the speed limit, you'll cruise down the road.

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