By Darren Waters
Technology editor, BBC News Interactive
Car manufacturers around the world are working on vehicle-to-vehicle technologies to help make driving safer. How will they work? And what difference will the technology make to our experiences on roads?
The car in which I am travelling is moving towards a T-junction at speed, with the driver seemingly oblivious to the need to brake.
Out of the corner of my eye I spot a second vehicle heading along the road to our left on a collision course. Seconds before an almost fatal accident is set to occur the vehicle-to-vehicle system sounds an alarm and an in-car display warns of the need to stop.
The driver hits the brakes and we come to rest before the junction. The second car has also slowed after receiving a warning about a potential collision and passes by without incident.
The near-collision warning is a demonstration of technology that is expected to be rolled out to all shapes and sizes of cars in the coming years.
It is being developed by the European Car-2-Car consortium and is backed by General Motors, Audi, BMW, Fiat, Honda, Renault and a range of in-car hardware manufacturers and several universities.
It is hoped vehicles will be able to use wi-fi to share details on speed, direction and roads. It may improve safety and ease jams.
If likely to hit car ahead, alarm sounds and seat vibrates. Tail lights of stationary, braking or slow car flash and warning sent.
Driver heading for junction at speed told to brake and stop. Driver on main road warned a car may pull out and told to brake.
Warning light on mirror shows if another vehicle in blind spot. If driver signals lane change, light flashes and seat vibrates.
Cars share information. After passing fog and traffic jam, car tells others heading towards it - which can choose a new route.
"Drivers are supposed to have the leading role. In this system, drivers always maintain control."
The Car-2-Car Consortium's system, which includes GM's Vehicle-to-Vehicle project, combines three technologies - a Global Positioning Satellite (GPS) antenna, a wireless data system and a computer that interprets the information it receives.
GPS tracks the position of the car while sensor data from the car - such as speed, direction, road conditions and if the windscreen wipers are on and if the brakes have been stamped on - is monitored by the on-board computer.
A wireless system similar to existing wi-fi technology - based on the 802.11p protocol - transmits and receives data to and from nearby cars, creating an ad-hoc network.
Data hops from car to car and the on-board computers can build a picture of road and traffic conditions based on information from multiple vehicles across a great distance.
Cars travelling in opposite directions can share information about where they have been and so informing each other about where they are going.
Traffic information about roadworks and speed limits can be displayed
"The wireless system has a range of 500m outside the city and 100m in the city," said Prof Wieker. He said the consortium had opted for wireless rather than a mobile network because it was faster.
"The data moves between cars in milliseconds," he said.
Drivers receive warnings through messages on an in-car display, audio alerts and even seat vibrations.
The system works through "data fusion and logical combination of information", said Prof Wieker.
For example, if one driver switches on his fog lamp and slows down, the computer could interpret it as an anomaly. But if three or four cars follow suit, the computer could reasonably assume that there is a fog problem.
The system stores this information and passes it on to cars several kilometres down the road which are travelling in the opposite direction, heading towards the fog problem.
"It is useful not only as a safety system but could also be used to improve traffic efficiency," said Prof Wieker.
The backers envisage the technology being embedded into traffic lights and road signs so that real-time traffic information can be passed to cars, potentially funnelling motorists to alternative routes.
At a test day of the technology, the system was shown warning drivers of cars broken down around bends, the direction of oncoming emergency vehicles, warnings about road works and advice on speeds and lane closures.
Wireless antennas can be embedded in roadworks infrastructure and traffic lights
"We are working with psychologists to ensure the warning information given to drivers is appropriate," said Mr Praunsmandel.
The next stage is a live trial in Frankfurt with 500 to 1,000 cars equipped with the technology.
Despite being based on existing technologies, the project has hurdles to overcome, including working with similar schemes under development in North America and Japan.
Only recently did the consortium agree upon a frequency for the wireless system which successfully avoids interfering with other uses of the technology across Europe - such as emergency vehicle radio bands, military uses, etc.
The backers have not committed to a roll-out date but insist it will be inexpensive because it is based on off-the-shelf technologies.
Mr Praunsmandel said: "We're committed to ensuring that the technology is affordable for all car owners. That's our goal."