The system, to be introduced in a new vehicle this summer, adjusts the speed of the car to match that of the vehicle in front, even as low as zero to 30 kilometers per hour (19 miles per hour), the carmaker said.

If the vehicle in front stops, the system brings the car gently to a halt if the driver does not respond to visual and audio warnings in time. Depending on one's speed, the distance from the preceding vehicle can be set to between 17 and 50 meters (19 and 55 yards).

The cruise control does not automatically accelerate again to keep up with traffic flow, however.

"The premise is that the driver is still in control," said Toyota Motor Corp. spokesman Hitoshi Nagashima. "If the car in front stops and then starts moving again, the driver must step on the accelerator to get moving again."

Drivers on Tokyo's crowded expressway system spend about 32 percent of their time at such low speeds in weekday conditions, Toyota said.

Toyota's previous radar cruise control system works at speeds of 40 to 100 kilometers per hour (25 to 62 miles per hour) and has been sold for 70,000 yen (640 dollars) in Celsior luxury sedans in Japan since August 1997.

The company did not say how much the new system would sell for, or if it would be sold on models outside Japan.

SPACE.WIRE