Since we're close to the topic, it's interesting how racing tragedies change the sport and occasionally history in general.
While it's not modern racing, this one had a major effect beyond the sport.
A sport called motorpacing was very popular before WWI especially in Europe. It's basically a combination of bicycle and motorcycle racing. The bicycle rider follows the motorcycle around the track at high speed. Typically around 40, but sometimes a lot higher. The riders were very well paid.
On June 18, 1909 at Berlin, one of the motorbikes - then huge specialized things often with a driver and a heavy guy on the back to make a bigger windscreen- along with he bike rider went into the crowd and caught fire.
9 killed and by some accounts 52 injured.
Prussian authorities banned motorpacing, and overall the sport lost much of its popularity.
It had always been dangerous, but was becoming less manageable. (The berlin track was also massively substandard for that sort of racing even by the loose standards of the time. )
As the sport became less popular, and fewer races were held, the riders began moving on to other things to make money. Some went into racing motorcycles, others got in an entirely new field that promised similar money with occasionally less risk. Early aviation! Many motorpace riders became pilots doing the rounds of the air shows. Best of all, the money was appearance money and a plane that actually flew wasn't necessarily a requirement. Many did fly, and at the time, that was also risky. Those early aviators provided a core of experienced pilots when WWI put and end to the air show circuit.
The sport survived, had a decent revival in the 30's as part of 6 day races, and is still done today.
Here's a motorpace bike from probably the early 30's.
Steve B