Safety Question

[Willy29]

When did the safety rule change for disabled cars on track?
The 1979 Monaco race on the second last lap, the leaders passed a disabled car.
I watched a lot of races back then (obviously not this one), at least one a year, when at Mosport. I was young then, but didn't see a race continue normally with a disabled car on track.
When did the rule change for disabled cars, on track for a hot race?
I'm a marshal at CTMP (Mosport).