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Status Report, Vol. 45, No. 10 | September 28, 2010 Subscribe

Double-red signal reduces crashes at crosswalks

A relatively new type of crosswalk signal that stays dark until a pedestrian activates it can reduce crashes at intersections where a full-fledged traffic signal isn't warranted, a study sponsored by the Federal Highway Administration has found.

The High-Intensity Activated Crosswalk, or HAWK, beacon consists of 2 red lights over 1 yellow and is typically marked with large pedestrian crossing signs. When a pedestrian presses a button, the signal flashes yellow, then switches to solid yellow. Then both red lights shine, and pedestrians can start crossing. Finally, the device switches to flashing red, meaning drivers can proceed as soon as pedestrians have cleared the lane.

The city of Tucson, Ariz., developed HAWK signals in the late 1990s and now uses them at more than 100 sites. Other cities have since adopted HAWK, also known as a pedestrian hybrid beacon. Less expensive than full signals, HAWKs have been shown to be effective in getting drivers to yield to pedestrians on major streets with multiple lanes or high speeds, and they're being tested for use at roundabouts. The flashing red phase allows vehicle traffic to resume quickly.

Traffic engineers have several tools to help people cross a major road. A familiar one is a standard, red-yellow-green traffic light that remains green until a pedestrian pushes a button. However, under the Manual on Uniform Traffic Control Devices, such signals should only be used midblock. If a traffic light is at an intersection, it must be a full signal that controls the side street, too.

Tucson officials wanted to allow pedestrians to cross at intersections but didn't want full signals at residential side streets because they tend to encourage cut-through traffic. The solution devised by Richard Nassi, until recently Tucson's transportation chief, was the HAWK beacon. It controls traffic at intersections on main roads only, while side streets still have a stop sign.

The Federal Highway Administration's study, conducted by researchers at the Texas Transportation Institute, looked at 21 HAWK sites and compared the number of crashes in the 3-year period before the signals were installed with the number of crashes after.

The HAWK signals did their job. Pedestrian crashes near the intersections tumbled 59 percent, and other types of crashes also went down. Total crashes fell 14 percent, and severe crashes fell 13 percent. These results take into account changes in the number of crashes at nearby intersections without HAWKs or other traffic signals.

The study also examined a smaller group of crashes that were specifically reported as intersection-related. In this analysis, pedestrian crashes declined 51 percent, total crashes dropped 29 percent, and severe crashes fell 15 percent.

HAWK is rapidly gaining acceptance, and the pedestrian hybrid was included in the 2009 traffic control devices manual. However, recommended use differs from the practice in Tucson, where the vast majority of HAWKs are on major arteries at intersections where side streets are controlled by stop signs. The guidelines say the signals should be installed at least 100 feet from side streets or driveways controlled by stop or yield signs to avoid driver confusion.

Nassi says he expects the National Committee on Uniform Traffic Control Devices, of which he is a member, to ask the Federal Highway Administration to reconsider that guidance in light of the recent study.

"The perceived danger is not turning out to be a danger," he says. "HAWKs provide another pedestrian safety tool at both intersections and midblock locations."

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