Official explanation:

The first target was to minimise the energy forces on the occupants of the car during a collision. This is achieved through greater survival space as well as energy absorbing material and a load spreading door cage.

The next priority was strengthening the driver’s seat to improve head, shoulder and pelvic support. The seat is important because it is the main connection between the driver’s body and the car. It also provides the last line of protection should an accident occur.

The safety nets, still under development with the teams, will be placed along the centre-line of the car, between the driver and co driver, in order to limit the excursion of the occupants, and prevent them impacting each other during a violent impact or roll.

The belt positions have been specified to create optimised belt strap geometry and angles which ensure the torso is efficiently and equally restrained by each of the straps of the safety harness.

The load spreading door system will increase the strength of the car in the region of the front doors, and will reduce the intrusion during a side impact accident.

By introducing these measures in stages, the rally teams are able to incorporate them more easily into the designs of their car.

Much of the research was conducted in co-operation with Peugeot and Prodrive, with engineering design by the Subaru World Rally Team. A high-g sled at DEKRA was commissioned for development testing where it was demonstrated that a high velocity 70g side impact could be survived without serious injury.