I always leave a couple feet in case the car ahead of me stalls out or becomes otherwise immobile (like a driver dreaming of Planet Mongo as the light changes), enough room to turn into the next lane and go around. I don’t tailgate and tailgaters riding my @$$ are subject to random brake testing.
That was the EXACT situation I was in last evening on my way to work: the car in front of me in the left-turn lane stalled and couldn't restart. I had left enough room that I was able to go around the stalled car in the F-350 longbox crewcab.