New Volvo Braking System Hopes to Cut Collisions in Half

Volvo Cars has unveiled a new system that can help drivers avoid the low-speed collisions that are so common in urban traffic and in slow-moving traffic queues.

The system is called City Safety, and its premise is simple - if the driver is about to drive into a vehicle in front of it and does not react in time, the car brakes itself. Volvo plans to introduce City Safety to the market within the next two years. The manufacturer hopes it will help avoid half of all rear-end collisions.

"The system offers benefits to all involved," says Ingrid Skogsmo, director of the Volvo Cars Safety Centre. "For the occupants of the car in front, the risk of whiplash injuries is avoided or reduced. What's more, the system can help reduce or sometimes even eliminate the cost of repairs to both vehicles."

If the vehicle in front suddenly brakes and the City Safety senses that a collision is likely to happen, it will precharge the brakes to help the driver avoid an accident by braking, or let the driver steer away from a potential collision. However, when the system senses that a collision is imminent, the car will brake automatically through hydraulic pump activation. The system works equally well by day or night.

According to Volvo, statistics reveal that 75 percent of all reported collisions occur at speeds of up to 20 mph. In addition, the consequences of small impacts are often so limited that many are not reported to insurance companies. However, even the smallest collisions cost time and money to repair.

City Safety is active at up to 20 mph. If the relative speed difference between the two vehicles is below 10 mph, the system can help the driver avoid the collision entirely. Between 10 and 20 mph, the focus is on reducing speed as much as possible before the impact.

The system keeps a watchful eye on traffic in front of the car with the help of an optical radar system integrated into the upper part of the windscreen at the height of the interior rearview mirror. It can monitor vehicles that are up to 20 feet in front of the car, and the system is programmed to respond if the vehicle in front is either at a standstill or is moving in the same direction as the car itself.

Based on the distance to the object in front and the car's own speed, the system runs a calculation 50 times per second to determine what braking speed is needed to avoid a collision. If the calculated braking force exceeds a given level without the driver responding, the danger of a collision is considered imminent. In this case, City Safety helps avoid or reduce the collision by automatically activating the car's brakes or by auto braking and switching off the throttle.

City Safety has the same limitations as conventional radar systems. The sensor's capability can be limited by fog, mist, snow or heavy rain, so it's essential to keep the windscreen debris-free. If the sensor is blocked, the driver is alerted via the car's information display.

"It is important to emphasize that the system does not absolve the driver from driving with adequate safety margins in order to avoid collisions," says Skogsmo. "The automatic braking function is only activated when the system assesses that a collision is imminent. The system then steps in to limit the consequences of - or in some cases totally avoid - the imminent collision."