Smarter way to catch lights

Japanese technology developer Denso Corporation has come up with traffic lights that can "talk" to vehicles. Photo / Dean Purcelll

Japanese technology developer Denso Corporation has come up with traffic lights that can "talk" to vehicles.

The "smartlight" system is designed to improve traffic flow and cut the time traffic spends idling at lights, thereby reducing emissions and fuel useage.

It uses messaging between vehicles and the traffic-light controller to let the lights make better decisions about when to change.

As a rule, car-sensing lights stay green in one direction until a car wants to enter the intersection from the cross street, when the light is directed to change based on sensor data from a loop of wire in the road.

Denso's proposed system uses short-range wireless transmitters, like WiFi routers, in cars and the road infrastructure. The field is broadly known as V2V (for vehicle to vehicle) communications.

Traffic lights that "know" more about oncoming vehicles could change dynamically, based on approach speeds, vehicle types and volumes of cars approaching from any direction.

This would let a stoplight "know" that one vehicle was approaching from a given direction, and delay a regularly scheduled change long enough to let it pass through.

Two truck and trailers travelling one after the other could signal their presence to the light, allowing it to stay green in one direction long enough to let the pair pass through.

Data on whether a car was accelerating, braking, or flashing a turn signal would all factor into signal timing, including the duration of optional features like turning-lane arrows.

Some express city transit buses already carry equipment that lets them pre-empt changing traffic signals, to reduce time lost waiting at red lights. The theory is that a bus with 50 passengers should take priority over 20 single-occupant cars.

Denso's model, however, goes well beyond the signal-control algorithms, which use averages of traffic flow, to adjust cycle times and light extensions to get to the "state optimum" for any given set of upcoming vehicles.

The company has been testing both pre-empting red lights and extending green lights via transmitters onboard the vehicle and receivers in stoplights at its Vista, California, research facility.

Ultimately, not only vehicles but motorcycles and perhaps even bicycles might carry signalling transmitters to take their place in the data flow.

Accelerating away from traffic lights uses far more fuel than maintaining a steady speed. A V8 engine can briefly consume upwards of 80 litres/100km (3.5mpg) under a standing start. Denso also sees savings in the time commuters spend in traffic.

- AP