500 miles of racing's worth of debris not being cleaned off the track could arguably be more dangerous as you will have crashes from that every race. You can see it in endurance races that go huge gaps without cautions where they can blow off the track. A car takes a wide line to make a pass and loses control due to the marbles. They could go back to the old roller brushes but they were not as effective or quick.
Though I think a speed limit for cars catching up to the pack wouldn't be a bad idea. If pace speed is 70 then what is reasonably safe but still gives a decent opportunity to catch up?
But ultimately we are looking at a situation that had crazy odds of happening. The track is 13,200 feet long. A car is ~17 feet long. To have the accident happen at that exact moment to put 17 of 13,200 feet in the exact spot where that blower was is insanely crazy. If you consider that normally the cars are under, arguably, intelligent control the odds are even greater. And that is assuming the track is a single line. If I took the time to factor in square footage of the track and all runoff areas the odds would be comparable to winning the lottery.
