I'm curious how much of a buffer there is between the time the sensors detect the airplane and it being safe to enter the runway. Is it definitely safe to cros

I'm curious how much of a buffer there is between the time the sensors detect the airplane and it being safe to enter the runway. Is it definitely safe to cross the runway in a vehicle moving a normal speed up to the moment before the lights turn red? Is it safe for a little bit afterward? Or is it unsafe even a little before the lights turn red?