At the heart of the modern Formula One car lies the immensely strong 'monocoque' structure, often referred to as the 'tub'. This incorporates the cockpit and the driver's 'survival cell', but also forms the principal component of the car's chassis, with the engine and front suspension mounted directly to it. Both roles - as structural component and safety device - require it to be as strong as possible.
Like the rest of the car, most of the monocoque is constructed from carbon fibre. Normally it comprises high-density woven laminate exterior panels, and a strong, light 'honeycomb' structure inside. Constructing the monocoque is one of the biggest jobs faced by a team's composite technicians. It's not dissimilar to a 1:1 scale model kit, with hundreds of separate carbon fibre components being bonded together using very powerful adhesives.
The fact so many Formula One drivers have survived enormous accidents is testament to the enormous strength of the survival cell. This, in turn, is a tribute to the teams' very real commitment to safety, but also the constantly evolving technical regulations (laid down by the FIA) which define the increasingly stringent safety requirements.
The fundamental principle remains, as always, that the driver should be able to get out in the least possible time - five seconds, according to the regulations, and without having to remove anything except the steering wheel. (The regulations also say that the driver should be able to put the steering wheel back on in another five seconds, vital for the safe manoeuvring of stricken cars near the track). Crash protection areas are incorporated into the front and rear of the survival cell, as is the mandatory roll-over protection hoop behind the driver's seat. In recent years effort has been concentrated on increasing the protection for drivers' heads - the area most vulnerable to harm by flying debris, by specifying taller and tougher cockpit side walls.
As with road-cars, all Formula One cars must pass several crash and loading tests before being passed fit for racing. It is no coincidence that the FIA is one of the active partners in the Euro-NCAP road-car testing programme. The impact tests require the car's survival cell to be attached to a special trolley with a 75 kg crash-test dummy in place - this then being collided with a solid object at a speed of 15 m/s (54 km/h, 33 mph), with the forces applied to the dummy and the trolley carefully measured. The low speed of the test is no reflection on a Formula One car's ability to absorb the forces of larger impacts - the speeds have been chosen to allow the most accurate measurement of the car's ability to safely absorb the unwanted momentum of an accident. Rear impact and steering column loading tests are also carried out.