The belief that technology can improve roadway safety is driving public- and private-sector officials to test intelligent transportation systems that allow vehicles to communicate with the transportation infrastructure. And some of the biggest beneficiaries of these efforts could be first responders speeding to an emergency scene and the motorists they encounter en route.
In 2009, an estimated 33,403 emergency vehicles were involved in accidents, 126 of which were fatal, according to the National Highway Traffic Safety Administration. Systems are being developed to let emergency vehicles and passenger cars interact with traffic signals and other transportation infrastructure in ways that get emergency crews on-site quickly while safeguarding other motorists. One such project, for example, seeks to make intersections safer, while another will alert motorists when an emergency vehicle is approaching.
“The bigger goal from a public agency perspective is to improve the safety drastically as well as improve the mobility,” said Faisal Saleem, intelligent transportation systems branch manager for the Maricopa County, Ariz., Department of Transportation.
Pre-empting Traffic Signals
Maricopa County is using dedicated short-range communications to improve safety at intersections. As part of a research project through the U.S. Department of Transportation’s IntelliDrive program (formerly the Vehicle Infrastructure Integration initiative), the county is equipping six intersections and numerous emergency vehicles with technology that allows them to exchange information.
Emergency vehicles currently use infrared light to pre-empt traffic signals, which Saleem said is basically like a remote control. A flashing light above the traffic signal indicates that the request has been received. But there’s an issue when more than one emergency vehicle tries to pass through the intersection. “It is on a per vehicle basis,” Saleem said, “so if there are two vehicles approaching the intersection from two different directions, there have been cases of collisions because each one is expecting that they will get the pre-empt.”
Maricopa County’s project — which began three years ago and involves numerous agencies, including the Arizona Department of Transportation, the University of Arizona, Arizona State University and private partners — seeks to create a system that will handle multiple pre-emption requests and serve them based on priority.
Dedicated short-range communications run on a frequency the FCC has allotted to transportation operations, Saleem said, and intersections and vehicles involved in the project will be equipped with short-range radios. “It gives the ability to communicate between vehicles and infrastructure at a very low latency,” he said. “In about a second, you can have about 20 messages exchanged between the vehicles, as well as between the vehicle and the infrastructure.”
Messages will request service and tell the traffic signal what type of vehicle is approaching, said Larry Head, associate professor at the University of Arizona’s College of Engineering. The university’s research has focused on how to take the vehicles’ requests and determine the best way to time the traffic signal to serve them.
“We have an algorithm that bases it on priority, arrival time, current state of the signal controller and its ability to respond to the request,” Head said. This ensures that no request will violate the minimum time that green lights are required to stay activated.
The real-world testing will take place at six intersections and was scheduled to begin in July or soon after. Saleem said the Transportation Department will examine how far from the signal the notification is received, and the processes of changing the traffic light and providing pre-emption. “Any response vehicle that is out on the roads, we are trying to see if they could respond more safely as well as reduce their response times,” he said.
The outfitted intersections also will be used as test beds for other projects, like transit priority for school buses and government vehicles.