Volvo Cars' unique City Safety feature will be introduced as a standard equipment
in the new Volvo XC60, which reaches the showrooms in the end of 2008.
City Safety can help the car driver avoid rear-end collisions in low speeds.
If the driver is about to drive into the vehicle in front and does not react in time,
the car brakes itself.
Volvo Car estimates that the technology has the potential to prevent half of all rear-end collisions.
"The function offers benefits to all those involved. The risk of whiplash injuries is avoided or limited
in both vehicles. City Safety can also help to reduce and at best eliminate the costs of repairs to both vehicles," says Jonas Ekmark, manager for Preventive Safety at Volvo Cars Safety Centre.
If the vehicle in front brakes suddenly and City Safety calculates that a collision is likely, the brakes will be prepared to help the driver to avoid the collision by braking more effectively. If City Safety senses that the driver needs additional help, the car will brake automatically through hydraulic pump activation.
According to statistics, 75 per cent of all reported collisions occur at speeds up to 30 km/h (19 mph). Furthermore, the consequences of minor collisions are often so limited that they are not reported to insurance companies. However, even the smallest impact costs time and money to rectify.
City Safety is active at speeds up to 30 km/h (19 mph). If the relative speed difference between the vehicles is slower than 15 km/h (9 mph), it can help the driver to avoid a collision completely. Between 15 km/h and 30 km/h the objective is to reduce the speed as much as possible before a collision occurs.
Laser sensors monitor the traffic in front
City Safety keeps an eye on the traffic in front with the help of a laser sensor that is built into the windscreen's upper section at the same height as the rear view mirror. It can detect vehicles that are up to 6 metres in front of the car's front bumper.
City Safety is programmed to react to vehicles in front that are either stationary or moving in the
same direction.
On the basis of the distance to the object in front and the speed difference, the function makes
50 calculations a second to determine the braking force is required to avoid a collision.
If the calculated braking force exceeds a given level without the driver reacting, it interprets this
as an imminent danger of a collision.
City Safety then helps to avoid or reduce the consequences of a collision by preparing the car's brakes or braking automatically and disabling the accelerator.
Certain limitations
City Safety has the same limitations as all optical technologies in that the detection capacity can be limited by fog, snow or heavy rain.
It is therefore necessary to keep the windscreen free of dirt, ice or snow. If the sensor is blocked, the driver is advised via the car's information display to clean the area. City Safety works equally well during the day and night.
"It is important to underline that City Safety does not relieve the driver of the responsibility from maintaining a safe distance to avoid a collision. The automatic braking function does not react until it considers that a collision is imminent. City Safety will help to limit reduce the consequences or completely avoid an imminent collision," says Jonas Ekmark.
