Avoiding Red Lights by Booking Ahead

Discovery News | By Jesse Emspak

A computer program that reserves slots at an intersection might be a way to ease gridlock and boost safety.

  • Future cars could be equipped with computer systems that
    "call ahead" to intersections.
  • The intersections can then reserve a green light for the
    approaching vehicle.
  • The concept could avoid gridlock and reduce collisions,
    claims a computer scientist.

Computers can reserve your plane ticket, your hotel room and your restaurant table. Why not your place at an intersection?

The concept is simple: a computer in a car calls ahead to the nearest intersection it is headed toward, and says it will arrive at a given time. The intersection checks to see if anyone else is arriving then, and if the slot is open, it tells the car to proceed. If it isn't, it tells the car that and the car is responsible for slowing down or stopping.

That's the idea Peter Stone, an associate professor of computer science at the University of Texas at Austin, is presenting at the American Association for the Advancement of Science.

Rather than trying to keep track of all the cars on the road, all the intersection's computer does is say whether there is a space for the next vehicle, given a list of time slots.

"It's a bit like reserving at a hotel room," Stone said. "When you call a hotel and say you are arriving Friday, they check to see if there is a room. They don't call up everyone else at the hotel and ask them to change their travel plans."

If there is no room, the traveler changes the arrival date or finds another hotel. The intersection would work in a similar fashion.

Cars are becoming more sophisticated, and there is already a lot of work being done networking cars (including at least one concept model from Ford ). Integrating them with the traffic signals isn't a large step, and that could boost the efficiency of traffic, as well as safety.

The Department of Transportation reported that in 2009 there were 5.5 million car crashes and 2.2 million were at either an intersection or "intersection related." Of those accidents, 699,000 resulted in injuries, and 6,770 resulted in deaths.

Part of the reason intersections are dangerous — in some cases more so than highways — is because the vehicles are going in different directions, so sideswipes are more common. When cars collide, a thin door is much less protection than an engine block. But the other major factor is human behavior.

Green lights are designed to operate in waves that allow cars traveling at a set speed to travel freely for some distance, but few ever keep to that speed — one person is going faster and another slower, and it isn't long before the smooth flow of traffic is a mess.

Stone wanted to solve some of that and keep the computing complexity to a minimum. One could, Stone said, link the intersections as well, so that along certain routes they could coordinate traffic flow. (If such an intersection's computer were to fail it would be no different than when traffic lights go out).

Others in the field are working on similar problems. Denis Gillet, associate professor of information systems at Switzerland's Ecole Polytechnique Federale de Lausanne, noted that vehicles could do a certain amount of "planning ahead" for their trajectories, by exchanging information with each other.

Gillet said the idea in any of these systems is to get vehicles to slow down, but not stop, because slowing and stopping is not very energy-efficient.

Philip Tanoff, who recently retired as director of the Center for Advanced Transportation Technology at the University of Maryland, is skeptical that such a system could work with only a few cars equipped to signal the traffic intersection.

"It seems that it would work only under optimal conditions," he said. Though the onus of adjusting speeds and arrival times (or stopping) is on the cars, the question, he says, is whether they could account for many other factors on the road — pedestrian traffic, for instance, crossing at a crosswalk.

Stone said his technology can work with even just a few vehicles linked to the intersections, since the car can still take into account what the (unconnected) ones around it are doing.

"The benefits are less when there are human drivers," he said. "But it is still safer."

Stone is also researching methods of dynamically changing the number of lanes in each direction on major roads to respond to traffic flows.

Altering the lanes is familiar to anyone who has driven into New Your City's Lincoln Tunnel, or seen the huge machines moving barriers on New York's Tappan Zee Bridge. In this case, a combination of lane changes and managing traffic flows at the intersections could mean better traffic flows through a city.


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