Automated sensors are watching out for you

Take a walk down most busy urban streets and you’ll see any number of traffic devices to help keep pedestrians and bicyclists safe — pavement markings, crossing signals and warning signs. What you don’t see is what goes on behind the scenes.

Several traffic safety devices need sensors that can detect pedestrians and bicyclists reliably and accurately. The effectiveness of these safety measures depends on how well the sensors actually work. Recently, researchers at the Texas Transportation Institute (TTI) developed a real-world test bed to evaluate pedestrian and bicyclist sensors, with funding from the Southwest University Transportation Center.

Intersection-Based Sensors

At some intersections, pedestrians can push a button, which tells the signal controller to provide a walk signal. With accurate sensors, pedestrians wouldn’t even have to do that.

Detecting a pedestrian, the signal controller could give the walk signal and even extend the pedestrian walk time, which would be especially useful for people who walk slower than average, such as the physically disabled and the elderly. The signal controller could also provide an advance warning to pedestrians or motorists of potential conflicts.

TTI Research Engineer Dan Middleton worked on the project with Research Engineer Shawn Turner. “A more important application of the sensors is at places where there are no signals, such as at a crosswalk or unsignalized intersection,” says Middleton. “On a busy street, a pedestrian will wait for a gap. But the longer the pedestrian waits, the more likely he or she is to take more risks and start the crossing in a short gap of traffic.”

At these areas, sensors can trigger flashing beacons to warn motorists that pedestrians are in the crosswalk or intersection. Motorists would have time to slow down and stop for pedestrians, especially in high-speed areas.

Trail Counters

Transportation agencies need data on the number of pedestrians and bicyclists using crosswalks, sidewalks, paths and trails. Traffic counts can tell them the potential crash exposure for a given trail and if the trail needs further safety enhancements.

“If agencies make improvements, they want to be able to show that fewer people are getting injured,” says Turner. “However, once the improvement is in place, more people may be using the trail because they feel safer. Just looking at the number of crashes before and after an improvement can be misleading. We need to look at the crash rate, which accounts for more (or fewer) people crossing the street after the improvement.”

With the current emphasis on promoting alternatives to vehicle travel, especially modes that have less of an impact on the environment, agencies are taking a closer look at including pedestrians and bicyclists in their transportation plans.

“We need to study walking and bicycling in the same way we study vehicles,” says David Ragland, the director of the Traffic Safety Center at the University of California-Berkeley, who is also doing research into the pedestrian and bicycle modes of transportation. “We have a set of requirements in place to measure vehicle volumes, and we need the same for pedestrian and bicycle counts. Those measurements are used for resource allocation, as well as risk assessment and planning.”