Why track safety comes first 17 Aug 2006
Some of the most important safety features in Formula One racing are alongside the track. Generous run-off zones help reduce the speed of a car that has come off the track, while tyre stacks absorb the impact energy of the car when hit. Both the run-off zones and tyre stacks play a crucial part in the high safety standards of top-class motor racing.
Although the safety systems at Formula One tracks have been greatly improved in recent years, the authorities refuse to be completely satisfied with the progress. Williams engineer Frank Dernie is not the only one to demand that the improvement of track safety must remain an important development goal in Formula One in the future.
If the car comes off the track because the driver has misjudged a braking point or is struggling with a technical fault, the run-off zone acts as a sort of emergency brake. The gravel traps are about 25 cm deep and filled with spherical gravel stones with diameters of between 5 and 16mm in diameter.
The stones are designed to generate as much frictional resistance as possible - like sand scattered on an icy pavement - and so reduce the speed of a skidding car quickly and effectively. However, there is often a practical problem with this concept: with a ground clearance of just 50mm and a smooth underbody, the cars often slide over the surface of the gravel trap without braking sufficiently.
There is also the danger they can be flipped by the heaped gravel and roll over. The loose gravel traps are therefore being replaced by rough tarmac. It has the advantage of allowing the drivers, in some cases, to bring their skidding car back under control. Moreover, if the car does roll, the roll-over bar does not sink into the soft surface: another safety bonus for the drivers. Williams driver Mark Webber, speaking to team sponsor Allianz, thinks run-off zones made of tarmac are safer, but makes an important point: Many drivers exploit that, and sometimes even overtake. In that way, they take a much bigger risk because the consequences of a spin are not so dramatic.
Run-off zones are not a logical option on every section of track. For acute impact angles of less than 30 degrees, the FIA recommends a smooth, continuous and vertical track boundary. Ideally, the cars slide along this wall or crash barrier and dissipate energy and speed. For less acute angles, on the other hand, gravel traps and tyre stacks are absolutely indispensable. A tyre barrier has to be at least as high as the boundary wall behind it (at least one metre) and must consist of between two and six rows of tyres. Normal car tyres are often used, but they must not be too worn to ensure they provide enough resistance in an impact. All the tyres have to be bolted together: the front row is covered and reinforced with a 12 mm-thick rubber strap. Ideally, tyre stacks absorb about 80 percent of the impact energy.
On some sections of the city track in Monaco, which is lined with 32 kilometres of crash barriers and has hardly any run-off zones, full water tanks have been used since 1995 as an alternative to tyre stacks. So-called soft walls were developed for the full-throttle banked corner at the Indianapolis Motor Speedway, filled with compact sheets of a polystyrene-like synthetic material and secured to the concrete wall with metal cables. Because it is a continuous system, it yields as a single unit in the case of an impact: the car does not get jammed and can slide smoothly along the barrier and slow down. Air-cushion fences are still in the test phase.
Whichever system finally asserts itself in Formula One racing, one thing is certain: the race to optimise track safety will never cross the finishing line.