Drivers who doze off or are taken ill at the wheel could be saved by a new system that detects signs of sleepiness or inattention.

The technology, developed by Toyota, works by monitoring the driver's eyes with a camera mounted on the steering column.

The camera works as part of an integrated driving safety system that also measures the distance to nearby vehicles with millimetre-wave radar and external cameras.

"Driver-condition evaluation technologies are vital to improving overall vehicle safety performance, as driver condition is a key factor in traffic safety, with driver error being the main cause," Toyota said in a statement.

By determining the driver's normal upper and lower eyelid position, the system can detect whether the driver shows signs of falling asleep, such as when the eyes close or partially close for a long period.

Toyota claimed that the camera can also detect whether the driver's face is no longer facing forward.

Initially, the system sounds a warning alarm and flashes a light. If the driver does not become alert, or the radar detects an imminent collision, the system can apply the brakes. The braking force depends on the proximity to other vehicles or obstacles.

Toyota announced initial versions of the obstacle detection and automatic braking parts of the technology as early as 2003, but the full system has not yet been applied to production vehicles.