New Volvo Car Technology Helps
Drivers Avoid Rear-End Collisions

Smart cars - they may be at local dealerships sooner than you think. For instance, within the next two years, Volvo Cars plans on rolling out their City Safety system that touts benefits to both drivers and passengers when faced with sticky driving situations.

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

If the vehicle in front suddenly brakes and the City Safety senses that a collision is likely to happen it will pre-charge the brakes to help the driver to 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.

Statistics reveal that 75 percent of all reported collisions occur at speeds under 20 mph. In addition, the consequences of small impacts are often so limited that not all are reported to the insurance companies. However, even the smallest collisions cost time and money to repair. City Safety is active at up to about 20 mph. If the relative speed difference between the two vehicles is below 9 mph, the system can help the driver avoid the collision entirely. Between 9 and 19 mph, the focus is instead on reducing speed as much as possible before the impact.

How does it work?

Optical Radar Monitors Traffic in Front of the Car
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 rear-view mirror. It can monitor vehicles that are up to 6 metres in front of the car. City Safety operates at speeds of up to 30 km/h 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 such a case, City Safety helps avoid or reduce the consequences of a collision by automatically activating the car’s brakes or by auto braking and switching off the throttle.

Certain Limitations
City Safety has the same limitations as all conventional radar systems, that is to say the sensor’s capability can be limited by fog, mist, snow or heavy rain.

“It is important to emphasise that the system does not absolve the driver from driving with adequate safety margins in order to avoid collisions. 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,” explains Skogsmo.

Preventive system in focus

Volvo Cars has previously presented active safety systems that help the driver avoid and reduce damage and injuries from collisions. One example is the current Volvo S80's Collision Warning and Brake Support that alerts the driver via audible and visual signals if the gap to the car in front is being reduced so quickly that an impact is likely. At the same time, the braking system is prepared so that braking is as effective as possible in this emergency situation.

(Source: Volvo Cars)