This is EXACTLY why I have a fire extinguisher in my car, and a small one in the saddle bags. Got them at WallyWorld pretty cheap.
About 6 years ago, I was driving to work (pre-bike) and a lady ran the light exiting from the highway.
3 car crash leave woman dead
I was 30 yards behind the car that was hit, and the first one to get to the car right after the accident. I was a Corpsman in the navy so the blood and guts don't scare me, but fire is a whole other story. There was thick smoke coming from under the hood, and I could see flames under there too. I grabbed my extinguisher from the trunk and emptied it under the hood, then went around to the passenger window render aid (she was slumped all the way over in the passenger seat - alive, just barely).
The fire trucks arrived about 8 or 9 minutes later, and they told me that if I had not had the extinguisher, the car would likely have burned all the way through. I remember rolling up to a crash scene in Okinawa and seeing a car completely engulfed in flames, with the driver still belted in. Absolutely horrific.
A $15 fire extinguisher can give you a few minutes to get people out. Go get one - soon.
Doc