City Safety reduces low speed accidents on Volvo’s XC60 and S60

It was four years ago that Volvo introduced its City Safety collision avoidance system which is designed to reduce the number and severity of low-speed accidents to the US market. However, a study in America by the Highway Loss Data Institute (HLDI) has shown that the results may not be as good as initially indicated by an earlier report.

According to 609 Volvo, statistics show that 75% of reported collisions occur at speeds of up to 30km/h (18.6mph) typically in urban traffic and in slow-moving traffic queues. In its 2007 report, HLDI found that front to rear accidents accounted for half of all multi vehicle accidents although these were not necessarily at low-speeds.

However, Mike McCarthy, head of active safety at the Transport Research Laboratory in the UK, says the figures can be deceiving as not all low-speed accidents are front to rear shunts. Accidents involving crossing traffic, occurring as the vehicle is turning a corner, during reversing or on icy roads could be low speed but would not be addressed by the City Safety system.

It was back in 2009 that Volvo made its City Safety low-speed front-end collision avoidance technology as standard fitment on all XC60 SUVs sold into the US market. In 2011 City Safety also became standard equipment on Volvo’s S60 mid-sized luxury car.

City Safety operates at speeds of up to 30 km/h and uses a laser system integrated into the upper part of the windscreen to monitor vehicles up to 6m (20ft) ahead. Depending on the vehicle’s speed and the distance to the car in front, the system detects what degree of braking in needed to avoid an impact. This calculation is made 50 times every second to instantly detect when the car ahead slows or brakes and, if the braking required exceeds a pre-set level without the driver responding, the brakes are applied automatically 0.8 seconds before an impact.
Where the closing speed between the vehicles is less than 15km/h (9.3mph) the system can help the driver avoid a collision entirely whereas between 15km/h and 30km/h, the system will minimise the impact speed. More recently Volvo has increased the active range of the City Safety system to 80km/h (50mph).

The HLDI study compared accident frequency and severity of City Safety equipped Volvo XC60s with other midsize luxury SUVs while figures for the S60 were compared with other midsize luxury cars. For the CX60 this gave 52,050 vehicle years and 1,395 accident claims (between 2009 and 2012) while for the C60 the statistics were 18,033 vehicle years and 365 claims (2011 and 2012).

 The areas examined were bodily injuries inflicted on third parties, property damage (caused to other people’s vehicles or property) and collision coverage (damage to the at-fault driver’s vehicle).

 The benefits of City Safety are very evident in terms of bodily injuries. With the XC60 the frequency of bodily injuries claims was the lowest in its class – 33% lower than the average of its peers. The S60 also averaged 18% fewer bodily injury claims than the basket of other midsize luxury car although it was higher than some individual models in the group. While any reduction in bodily injuries must be welcomed, these figures are still well short of the 51% reduction found in the 2011 study.

 The frequency of property damage claims made by XC60 drivers was calculated to be 15% lower than with other comparable SUVs and again this figure was lower than the 27% reduction found in the initial report. Drivers of City Safety equipped S60s were the 16% less likely to make property damage claims but the cost per claim was actually 13% higher than those of comparable vehicles while with the XC60 the average claim was 1% higher.
Collision claims (repair of the driver’s own vehicle) with the XC60 occurred at a rate 20% lower than average while the figure for the S60 was down by 9% lower. In this area the XC60’s results were very close to that of the 2011 study. While not overlooking the benefits of the City Safety system, the results are less encouraging than the initial HLDI report on the XC60 published in June 2011.

As the technology becomes cheaper, McCarthy predicts that it is likely to be more widely used by other vehicle manufacturers. He says such a move would be particularly welcomed by the UK’s insurance industry where claims for whiplash injuries are currently running at 570,000 per year.

However, he says while the difference between the reductions in claims seen in the initial report and the latest statistics is probably because of greater quantities of data, it could potentially raise a more fundamental question: “Does this indicate that drivers are becoming reliant on the technology and paying less attention when they are driving in traffic?

“While City Safety may take care of tail-end shunts in traffic queues, an inattentive driver is more likely to be involved in other types of incident,” he says. He also believes the findings raise the question about ‘risk compensation’ where a driver is prepared to take a certain amount of risk and if the perceived risk is reduced in one area they will take more risks in another. “From a safety point of view the best systems are the ones drivers don’t know about,” says McCarthy.

Volvo’s Anders Eugensson says City Safety is designed to prevent over-dependency: “Our system only acts when it is too late for the driver to act. So while a collision may be avoided, the process is quite alarming to the driver – it is too uncomfortable for the driver to want to simply rely on the system stopping the vehicle while they let their attention wander onto other things.”

	Volvo XC60		Volvo S60
Vehicle Damage	Claim frequency (2011 findings)	Claim severity	Claim Frequency	Claim severity
Bodily injury	-33% (-51%)		-18%
Property damage	-15% (-27%)	-$42	-16%	$373
Collision damage	-20% (-22%)	-$450	-9%	-668

Eugensson is Volvo’s director of government affairs and has spent considerable time in Japan as its government has regulations specifically aimed to stop over-dependence on vehicle technology. “It took a couple of years but in the end we convinced them that our system did not create over-dependence and the regulations have been re-written taking in some of the results of some of our research.”

Such thinking may have implications for future ITS-based safety systems. According to McCarthy, systems that alert drivers avoid many complications: “Who is responsible if an ‘autonomous’ vehicle has an accident - the person in the ‘driving’ seat, the car manufacturer, the car-to-infrastructure data owner, the technology supplier? With driver warning systems the human is always ultimately making the decisions so that question doesn’t arise.”

This thinking is in line with Volvo’s which has stated that the ‘intelligence’ of the car should support the driver, for instance by monitoring drowsiness or distraction. It can also warn the driver when the distance to other cars is too short but it is not until the driver fails to react and a collision is imminent or unavoidable, that the car ‘takes over’ from the driver, for example by auto-braking. The lowered impact speed leads to less crash energy, which in turn increases the performance of the car’s protective safety systems such as seat belts, airbags and crumple zones.

Volvo takes collision avoidance technology to new levels

In 2010 Volvo introduced a system that detects and automatically brakes for pedestrians, and in the future it plans to introduce systems that warn drivers and auto-brakes for large animals and even auto-steers away from oncoming cars.

Central to the system is a radar unit integrated into the car’s grille, a camera fitted in front of the interior rear-view mirror and a central control unit. The radar detects objects in front of the car and the distance to them while the camera determines the type of the objects. For the auto-brake system to act both the radar and the camera must confirm the object and it is then possible to apply full braking power immediately. The technology also covers vehicles driving in the same lane.