A British firm has unveiled a sat-nav system that warns lorry drivers when they are approaching roads where they are at high risk of hitting a cyclist.

Navevo's device is currently limited to providing alerts in 100 danger spots in London, but the company hopes to extend the project in the future.

"I do believe this will save lives at some point," the company's CEO Nick Caesari told AFP.

"It does slow people down and increase their awareness of hazards in the road. Of course, we may never know if it has saved a life -- but if it saves even one person it will have been worth it."

Lorries make up just five percent of London's traffic but they are involved in half of the city's cyclist deaths.

Between 2009 and 2012 53 cyclists were killed on London's roads, of whom 28 had been hit by lorries.

Sat-nav or GPS devices are increasingly popular with drivers looking for directions, but Caesari said this was the first to give warnings that cyclists could be approaching.

The system works by providing visual and sound alerts to lorry drivers as they approach roads popular with both cyclists and heavy goods vehicles (HGVs).

The list of 100 danger spots is based on data provided by Transport for London, the city's transport authority.