The latest-generation Volvo XC90 features a crash prevention feature called ‘City Safety’ which basically performs auto brake functions. The City Safety function is active at speeds from 4 km/h and features the world’s first auto brake at intersections. The function is useful at busy city crossings and especially at highway crossings, where speed limits are higher.
The crash avoidance system gives the driver warning in case of a potential collision and if the collision is imminent but the driver fails to respond appropriately, it will apply the brakes automatically. City Safety is based on a combined camera and radar unit. The radar detects objects in front of the car and the camera identifies what type of object it is. The feature also works in darkness.
City Safety is explained in detail in the press release below.
CITY SAFETY BY VOLVO CARS – OUTSTANDING CRASH PREVENTION THAT IS STANDARD IN THE ALL-NEW XC90 – Press Release
Starting with the all-new Volvo XC90, City Safety becomes the umbrella name for all of Volvo Cars’ auto brake functions. The continuously enhanced collision-avoidance and mitigation technologies, which are standard in the XC90, include yet another Volvo world first: automatic braking if the driver turns in front of an oncoming vehicle.
“City Safety is one of the most advanced standard crash prevention offers you can find in a modern car. It addresses vehicles, cyclists and pedestrians in certain situations, day and night,” explains Prof. Lotta Jakobsson, Senior Technical Specialist Safety at Volvo Cars Safety Centre.
As the leader in automotive safety, Volvo Cars has been pioneering auto brake technologies since the first-generation standard brake support was introduced in 2006. Among the groundbreaking technologies is the first-generation City Safety, which was introduced as a low-speed auto brake solution in 2008.
Now, City Safety takes on an extended, all-new role as the umbrella name for all Volvo Cars’ auto brake functions. The system is active at all speeds from 4 km/h (2.5 mph).
Auto brake at intersections – a world first
The auto brake at intersections is a world first that deals with a situation that is a common scenario at busy city crossings as well as highway crossings, where the speed limits are higher.
“Our studies of accident data from this accident type show that an important number of these crashes could have been avoided or mitigated if the turning vehicle had been equipped with auto brake. The solution is yet another example of how our new technologies target substantial real-life traffic problems. This strategy moves us closer and closer to our ambition that by 2020 no one should be killed or seriously injured in a new Volvo,” says Lotta Jakobsson.
City Safety auto braking functions
The purpose of the advanced crash avoidance system is to assist the driver through an intuitive warning strategy and a brake support system. If a collision is imminent, the system will provide automatic braking when the driver fails to respond to the imminent threat. The focus is on avoiding the collision entirely or reducing the car’s speed as much as possible prior to the impact. City Safety addresses:
• Oncoming vehicles, including motorcycles and cycles, when the driver turns left (or right in left-hand traffic). City Safety detects a potential crash and brakes automatically in order to avoid a collision or mitigate the consequences of a crash.
• Vehicles, including motorcycles, travelling in the same direction. City Safety is able to avoid a collision if the relative speed difference between the two vehicles is up to 50 km/h (31 mph). At higher speeds, the automatic braking helps to reduce the consequences of the collision.
• Cyclists crossing the path of the car or suddenly swerving out in front it. Depending on the situation, City Safety is able to avoid a collision if the relative speed difference is up to 45 km/h (28 mph). At higher speeds, the automatic braking can mitigate the consequences of the collision.
• Pedestrians walking out in front of the car. City Safety is able to avoid a collision at speeds up to 45 km/h (28 mph). At higher speeds, the automatic braking can help mitigate the consequences of the collision.
Detection also in darkness
City Safety is based on a combined camera and radar unit integrated at the top of the windscreen, in front of the interior rear-view mirror. The latest technology upgrade is a smarter and faster high-sensitive, megapixel image camera combined with advanced exposure control. This makes the detection and auto brake technology work effectively also when driving in darkness.
The radar’s task is to detect objects in front of the car and to determine their position and movement, and the distance to them. The camera identifies what type of object it is. The technology continuously monitors the object – and a central control unit uses the camera and radar data to evaluate the risk of a collision and to initiate the most efficient counteraction.
In an emergency situation, the driver receives an audible alert combined with a haptic warning in the shape of a short braking pulse and a light flashing on the lower part of the windscreen.
If the driver reacts to the warning and starts braking, the system is programmed to automatically ‘fill up’ with more braking power if necessary. If the driver does not react at all, the auto brake is activated. Full braking power is applied approximately 1.0 seconds before impact.
Avoiding real-life accidents
“Statistics show that about 90 percent of all accidents are caused by distracted drivers. Since City Safety remains alert even if the driver is distracted or tired, it helps to bring collision figures down considerably. We have, for instance, seen a documented reduction in frontal collisions in low-speed car-following situations by over 20 percent*,” says Lotta Jakobsson. She concludes: “Our aim is of course to continuously extend the City Safety auto brake technologies to cover more objects and traffic situations.”
*Source: If insurance company, Sweden, 2012