Scientists hope to prevent hundreds of road deaths in Britain each year with a seatbelt that wakes motorists up when it senses that they are falling asleep at the wheel.

Devices implanted in the seatbelt and seat cover of a car will keep track of the driver’s breathing and heartbeat to catch signs of tiredness and set off an alarm long before the risk of an accident becomes critical.

In 2013 more than 1,700 people died in road accidents in Britain, and previous studies have estimated that fatigued drivers account for between a fifth and a third of all road deaths in Europe.

The approach of sleep slows people’s reaction times and makes it harder to concentrate, and the number of fatigue-related accidents peaks after lunch between 2pm and 4pm, with another spike in the early hours of the morning.

Truck drivers and shift workers are most likely to nod off at the wheel, and 85 per cent of the motorists who cause crashes through sleep or tiredness are male. Men under 30 are most at risk of fatigue on the roads.

Some car models already keep track of signs that suggest the driver might be falling asleep, including how well they stay in their lanes and how smoothly they accelerate and brake.

The seatbelt project, which is called HARKEN and is led by Spanish and Portuguese engineers, as well as scientists from the University of Manchester, aims to pick up telltale indicators from the driver’s body far in advance of any danger. The heart rate and the frequency of breathing fall as sleep approaches.

Made from “smart” fibres, the devices feed the driver’s vital signs into a dashboard display. The technology has been calibrated to eliminate the “noise” caused by the motion of the car.

The developers claim that the system is “completely unobtrusive” and close to fruition. The seatbelts have been tested on race tracks and are shortly to go on trial on Spanish roads.

José Solaz , of the Institute of Biomechanics in Valencia, said that early tests had yielded “positive and reliable results” and that he expected the devices to appear on the roads in the near future. It is not yet clear how much they will cost.

“The variations in heart and respiratory rate are good indicators of the state of the driver as they are related to fatigue,” he told The Daily Telegraph. “So when people go into a state of fatigue or drowsiness, modifications appear in their breathing and heart rate.

“[The device] can monitor those variables and therefore warn the driver before the symptoms appear.”

A team of scientists from Nottingham Trent University are working on a similar project in which electrocardiograms are embedded into the fabric of car seats, setting off an alert to pull over when the driver shows signs of sleepiness. If the alarm does not wake the motorist up, the system is designed to activate cruise control or other automatic driving technology.

The seat covers will be marketed at lorry drivers and the owners of luxury cars if they prove to be effective.