Just before the pile up, it shows the characters in their cars, the guy who has the longish hair (the one who later gets cut up by the barbed wire)is driving down the road in a convertible. Next time it shows him he sees the police car about to over-take him as he is trying to snort cocaine off his hand...and the car clearly had a roof. It's an old car so it couldnt have bene one of those with the folding roof. Something that should have easily been spotted!