The ‘Ditch’ test that Thor got so wrong is designed to replicate the bouncing movement when driving into an 800mm-deep ditch at 50mph and then impacting an embankment.
“We built a replica of a real-life scenario, which you do find on many rural roads,” says Thomas Broberg, a senior technical advisor for safety at Volvo. “As the car gets airborne, it is quite a rough event. The accident involves high speed, vertical loads and a hard landing, and the car’s occupants move around in many different directions. Injuries to the lower spinal area can occur in these types of collisions.”
Volvo has good cause to focus on this type of accident, says Broberg. “From our data, we see that from 1991 onwards that we have made significant improvements when it comes to reducing the total amount of injuries in total in our vehicles," he says.
“But if we look specifically at the type of injuries occurring in these types of run-off road situations, we have not made the same amount of progress in reducing them. So of course, working with our zero-fatality ambition, this is an area we have to address.”
Improving protection means pre-empting what might happen to the car and its occupants during the accident.
Having determined the chronology of such an accident and the forces at play, Volvo can set about trying to counteract its effects on the occupants. The first step is to develop sensor technology so that the car knows when it is leaving the road. This involves building up a data bank of scenarios that could occur on different roads around the globe.
“This is the type of complex scenario we have to tackle, but they are quite unpredictable, because if you look along the side of any road, there are so many possible scenarios that could unfold,” says Broberg.
The next step is to ascertain what protection the occupants require. Broberg says: “Occupant posture is an important factor in the injuries sustained, so by using electric seatbelt retractors, we can help position the occupant in these situations and keep them in a better posture during the sequence of events.
“We also have to address the vertical forces that cause a lot of the lower spine injuries that we can see in these accidents. To do that, we created a deformation element within the seat. We had to clear the packaging beneath the seat so there are no hard structures that the seat will actually hit as it deforms and absorbs some of the forces of such a hard landing.
“We are deforming steel within the seat in a very controlled manner, and what we saw in our tests is that we actually managed to reduce the vertical loads acting upon the occupants by up to one-third.”
Volvo has given these combined technologies the name ‘run-off road protection package’. It is being rolled out for the first time on the new XC90.
The company hopes the new technology won’t get tested out too much. Active safety systems such as lane departure warning and tired driver alert should help mitigate against such incidents even occurring.
As the first vehicle constructed around the new SPA underpinnings, the XC90 has a significant part to play in enabling Volvo to achieve its goal of ensuring no one is killed or seriously injured in one of its new cars by 2020.