April 18, 2009 -- Pity the poor pedestrian.
While vehicle drivers and their passengers are cocooned in a crash, people hit by a car have no such protection. Now that could change, thanks to a variety of systems that when built into a vehicle will improve a pedestrian's chances.
Every month approximately 3400 people are killed in traffic accidents on the roads in the US, and a similar number die in Europe. Some 30 per cent of the injuries sustained by this group are caused by an impact with a windscreen or its frame.
A Europe-wide collaboration led by Roger Hardy of the Cranfield Impact Centre at Cranfield University near Bedford in the UK has developed an experimental system for cars that aims to cut this death toll and reduce the severity of injuries.
When the system detects that the car is about to hit a pedestrian, it automatically raises the rear of the bonnet (hood), releasing a giant airbag in front of the windscreen.
The raised bonnet absorbs some of the energy of the impact, reducing the risk of serious injury to the pedestrian, says Hardy, whose project forms part of the European Union-funded Integrated Project on Advanced Protection Systems (APROSYS).
Technology Cushions to Reduce Risk of Injury
"If it's a large pedestrian or on a small town car, the airbag also provides a cushioning effect around the stiff peripheral regions [of the windscreen]," he says.
The airbag system used by Hardy was developed by the German company Takata Petri. To test its efficacy when combined with the raised bonnet, they were incorporated into a prototype Fiat Stilo by engineers at the Fiat Research Centre in Turin, Italy. The team then assessed the severity of head injuries in collisions with a dummy pedestrian.
A standard Stilo hitting a pedestrian at 40 kilometres per hour, so that their heads struck the back of the bonnet, would have a score of around 1000 on the Head Impact Criterion (HIC) scale - corresponding to an 18 per cent chance of a life-threatening injury.
For pedestrians hitting Hardy's bonnet, the scores were reduced to between 234 and 682, while the windscreen airbag scores ranged from 692 to 945.
Adaptive Bumper Systems Would Absorb Energy in Impact
Hardy's team has also helped to design a windscreen-mounting system to cushion impacts with the edge of the windscreen. This consists of a flexible Z-shaped section of metal, up to 15 millimetres wide, separating the windscreen from its frame so that it can flex inwards to absorb energy in a collision. The team say it could reduce HIC scores by more than 50 per cent.
Another APROSYS collaboration, led by Jürgen Gugler at Graz University of Technology in Austria, studied how changing the shape of the front of a truck could reduce harm to pedestrians. Computer simulations of 20 accident scenarios showed that a smooth sloping surface with a central bulge reduces the likelihood of a pedestrian involved in a front-end accident being run over by 80 to 90 per cent.
"A pedestrian is deflected to the side, rotated and pushed towards the ground," says Gugler. "You are out of the path of the oncoming truck."
Fiat researchers led by Roberto Puppini have also had some success in early tests of an adaptive bumper system.
Four gas springs kick in at speeds between 4 and 80 kilometres per hour to move the bumper forward so that it will absorb energy in an impact.
So will manufacturers actually build any of these safety innovations into their cars? Over the next two years, the European car safety watchdog Euro NCAP will be phasing the results of pedestrian safety tests into its main rating system.
Poor Euro NCAP test results are credited with helping to get some less safe car models withdrawn from sale. This suggests that buyers and manufacturers can be persuaded to take the safety of drivers and their passengers seriously, although it remains to be seen whether the welfare of pedestrians is as persuasive a selling point.
There is, for now at least, little else to encourage car-makers to adopt these safety devices.
"From the legislative point of view, there is not a huge incentive for manufacturers to use this technology currently," says Hardy.
Perhaps ultimately the law will have to step in so that external airbags and energy-absorbing bodywork improve pedestrian safety as dramatically as seat belts and internal airbags have reduced driver and passenger deaths.
Volvo: Goal for 2020 Is No One Killed or Injured in a Volvo Car
"Our aim for 2020 is that no one should be killed or injured in a Volvo car," says Thomas Broberg, a senior safety specialist at the company.
When Volvo launched its new XC60 car in November, it included as standard an automatic braking system it claims could prevent half of all low-speed rear-end collisions.
Called City Safety, the system uses a laser sensor to check the distance between the car and vehicles up to 10 metres ahead. Measuring the speeds of both cars 50 times per second, it calculates the braking force required to avoid a crash. If the driver does not react when the vehicle in front slows, the system applies the brakes.
The Volvo S60, which launches next year, is planned to be the first car to be fitted with full automatic braking to avoid collisions with pedestrians.
The system uses a combined camera and radar sensor to monitor any obstacle in front of the car. The radar measures how far away it is, while images from the camera are analysed by image-recognition software to determine what the object is.
Drivers get an audible and visual warning of a potential collision, and if they do not respond the system automatically applies the brakes.
Volvo says its system could totally prevent collisions with pedestrians in cars travelling at 19 kilometres per hour or less, and reduce the impact of collisions above that speed by 75 per cent. Unfortunately it does not work as well in darkness and in poor weather, when accidents are particularly likely.