Toyota will start building a safety system into some of its cars this year that monitors if a driver is clearly watching the road during situations when a crash may occur.

If not the system can automatically take countermeasures either to avoid a crash or lessen the impact.

The system is based around a camera that watches the driver's upper and lower eye lids to evaluate how attentive he or she is to the road ahead. It builds on a current system that measures the driver's head direction when driving.

The car's safety system continuously monitors the road ahead using a radar system, and if it determines a crash may be possible, it matches this with the driver evaluation gathered from the camera. If the driver doesn't appear to be paying attention it sounds a buzzer and warning light.

If things progress and a crash becomes probable then it also tries to gain attention of the driver by quickly applying and releasing the brakes. At this point the car's pre-crash brake assist system is also readied. When a crash is judged to be unavoidable the safety system engages the brakes and seatbelts for the collision.

Toyota hasn't yet announced which vehicle will get the system first but it could appear as early as the next few months in Japan. Earlier models of the pre-crash assist system without the eye monitoring are already available in some high-end cars both in Japan and some overseas markets. There are no concrete plans to put this latest technology in vehicles outside of Japan.

Toyota isn't the only car maker working on a safety system that monitors the driver's eyes. Last year Nissan demonstrated a similar technology that watches the driver's eyes for signs of drowsiness and, if detected, tugs on the seatbelt to wake the driver and plays an audio prompt to take a rest. The Nissan system, which is still a prototype, works continuously and doesn't take into account the current driving conditions.

The IDG News Service is a Network World affiliate.