How do you make vehicles operate efficiently in real-life traffic? That's a question Audi has been trying to answer since 2006, when it first tested its "Travolution" system, which involves the communication between cars and traffic signals. The system's ultimate goal is to reduce the amount of time spent at traffic signals and accelerating a vehicle, as well as cut a vehicle's fuel consumption.

Audi said last week it has improved upon the system it introduced four years ago. The automaker said it enabled 15 vehicles to communicate directly with 25 traffic signals in Ingolstadt, Germany, using wireless LAN and UMTS links.

The traffic signals transmit data that are processed into graphic form and shown on the car's driver information display screen. The graphics tell the driver what speed to adopt so that the next traffic light changes to green before the car reaches it. This speed, which keeps the traffic flowing as smoothly as possible, can then be selected at the adaptive cruise control - but the driver can also delegate this task to the car's control system.

If the car is stopped at a red traffic light, this transmits information via the car's computer on how long the driver will have to wait before it switches to green again. If, on the other hand, the car approaches a traffic light that is about to switch to yellow or red, the driver is warned by a visual or acoustic signal, or by a brief interruption to the flow of power from the engine.

Audi said this system could reduce waiting times at traffic signals and cut fuel consumption by 17 percent.