media bulletin – Volvo
City safety avoids low speed crashes!
8 December 2006
Volvo Cars has unveiled a unique system that can help the car driver avoid the sort of low-speed collisions that are so
common in urban traffic and in slow-moving traffic queues.
If the driver is about to drive into the vehicle in front and does not react in time, the car brakes itself. The system
is called City Safety and Volvo Cars' ambition with it, is to help avoid half of all rear-end collisions.
Volvo Cars plans to introduce City Safety on the market within the coming two years. “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 Centre.
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 of up to 30 km/h. 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 30 km/h. If the relative speed difference between the two vehicles is below 15 km/h, the
system can help the driver avoid the collision entirely. Between 15 and 30 km/h, the focus is instead on reducing speed
as much as possible before the impact.
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 therefore essential to keep the windscreen free from dirt, ice and snow.
If the sensor is blocked, the driver is alerted via the car’s information display to clean the windscreen. The system
works equally well by day or night.
“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 Ingrid 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. Collision Warning and Brake Support 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. The system has been introduced in the new Volvo S80.
ENDS