It is often said that F1 has suffered no fatalities since Roland Ratzenberger and Ayrton Senna in 1994, but that is unfortunately not true.
At the 2000 Italian F1, GP fire marshall Paolo Ghislimberti was struck by a wheel lost from Heinz-Harald Frentzen's Jordan and died at the scene. Just five races later, at the 2001 Australian F1 GP, marshall Graham Beveridge was fatally injured by a wheel from Jacques Villeneuve's car.
In both the aforementioned fatal accidents, a wheel became detached from a car as the result of a collision, although wheel tethers are fitted to prevent precisely such occurrences. But in the extreme violence of a collision, especially in the fairly common scenario of a car dragging along a crash barrier, the tethers can be severed.
The tethers are not attached the the rotating wheel of course, but to the hub it is mounted on. So if the nut securing the wheel to the hub comes adrift for any reason, the wheel is completely unrestrained and free to depart.
Precisely that seems to have happened to the seven-times former world champion Michael Schumacher before he had even completed his first qualifying lap for the 2011 Belgian F1 GP. Schumacher's car was immediately out of control and hit the barriers, bounced off, and then slid across the track before coming to rest in a gravel trap.
Colliding with the barriers presented no real threat of harm to Schumacher, for the modern F1 driver has excellent impact protection. The runaway wheel, however, was a most deadly threat to him and others. Happily, in this case the wheel came harmlessly to rest, but the outcome could have been very different.
If a wheel comes adrift from an F1 car travelling at 150MPH, it has colossal kinetic energy, in the region of 20,000 joules. Few of us use the joule measure of energy on a daily basis, so here are some comparisons.
A Colt .45 calibre automatic pistol typically fires a bullet with 540 joules of energy as it exits the muzzle.
The current NATO standard 5.56mm rifle round produces 1796 joules of energy at the muzzle.
You get the picture; a detached wheel is an extremely dangerous unguided missile, and being struck by one is highly likely to prove fatal. Trackside fatalities have been mentioned here, and as recently as July 2009, F2 driver Henry Surtees was killed by a detached wheel that struck his head during a race at Brand's Hatch.
The fact that the driver of an F1 car, or any open-wheel race car, has his or her head exposed is the factor considered most likely to cause the next driver death. Besides the risk from a loose wheel or other flying debris, a crossover crash in which one car rides up over another is thought to present extreme hazard.
After driver Felipe Massa was struck and hideously injured by a spring that had come adrift from Rueben Barichello's car during qualifying for the 2009 Hungarian F1 GP, the FIA mandated stronger helmet visors. Prompted also by the death of Henry Surtees, consideration has been given to fitting windshields, the purpose of which would be to deflect debris up and away from the driver.
Windshields would bring their own problems, not least the issue of keeping them clear of bugs, and they would not afford crossover crash protection. So for the time being, F1 drivers continue to take the risks associated with having the head exposed.
But the FIA really has no alternative to acting when death intrudes on the sport. Just as the loss of Ratzenberger and Senna forced the enactment of very welcome and effective driver protection measures, so a death by flying wheel or crossover crash would surely bring the grim prospect of bubble canopies for drivers.
Fans would not like canopies, the engineering problems would be immense, and the resultant cars would bear little resemblance to the F1 form factor we know and love.
Motor racing is an entertainment sport. In our increasingly risk-averse culture, to what extent will we accept people placing their lives in danger for our interest and amusement? The answer to that question may determine if F1 has any future.