Volvo's commitment to safety is as old as the company itself. As Assar Gabrielsson, one of the founders of Volvo, declared: "Cars are driven by people. The guiding principle behind everything we make at Volvo, therefore, is - and must remain - safety." The engineers' safety target for the Volvo S40 was as simple as it was challenging: to replicate the high level of safety offered by the much larger Volvo S80.

"This was a tough challenge and one that we approached in an entirely new way," says Thomas Broberg, Volvo Cars Safety Centre. In a compact bodyshell, the deformation must be absorbed in a much shorter distance than in a large car. The torsional rigidity of the current model is 68 per cent greater than it was for the original Volvo S40, which improves its crashworthiness. However, to achieve the desired deformation characteristics, Volvo's engineers had to adopt a novel and ingenious approach to the design of the frontal structure.

The structure of the Volvo S40 has been divided into different zones, and different grades of steel were employed in each area. The outer zones are responsible for most of the deformation, while those closest to the passenger compartment are designed to remain largely intact, protecting the occupants. The zonal system is one of Volvo's many patented safety designs:

Low-speed deformation zone - The front bumper incorporates a rigid crossmember of Boron steel (Ultra High-Strength Steel). This section takes the form of a 'crash box' which is capable of absorbing the forces of a low-speed collision without damaging the rest of the body structure. The crash boxes can then be replaced individually, reducing repair costs.

High-speed deformation zone - The straight sections of the side members are made of High-Strength Steel, which is optimised for high energy absorption. The addition of upper side members provides significant protection should the vehicle collide with, for example, a truck. This zone accounts for most of the deformation in a collision.

Back-up zone - The section around the A-pillar acts as a barrier for the passenger compartment. Made of extra high-strength steel, this structure is extremely rigid and also helps to prevent the front wheels penetrating the cabin.

Three-way attachment - A rigid cross-member connects the A-pillars and the lower side members. On each side they form a rigid three-way attachment, which helps to maintain the integrity of the cabin in a severe crash.

The Volvo S40's high-tech engines also make a valuable contribution to its crash performance. The five-cylinder units are 200mm slimmer than those found in the larger Volvo saloons and this helps liberate space between the engine and passenger compartment. In a collision, the engine can be pushed 150mm rearwards with many parts, such as the battery, designed to move to pre-destined positions, before the engine block makes contact with the cross-member near the bulkhead.

Many of the advanced interior systems from the Volvo S80 have been incorporated into the design of the Volvo S40. The steering column deforms by up to 140mm in a horizontal plane, so that the driver's airbag remains in the optimal position. In the event of a severe impact, the pedal assembly will also collapse to prevent injury to the driver's lower legs.