On Friday we went down the M1. It was all fine, really, even in that 15 mile 50mph section - until just before the M25 junction, when everything suddenly stopped. Teh gantry lit up 60, the next one 40, then traffic ground to a halt. As we edged forward we could see people doing odd lane swaps, until eventually we saw why - a car sidways on, another with its nose in the central barrier. A few others parked on the central shoulder, people walking about making phone calls. Must have happened nor much over a minute before we got there.
Coming back up on Sunday much the same thing happened, somewhere just past Luton. Everything slowed to a stop-start crawl, after a mile or so we came across a couple of bent cars.
Don't often get so temporally close to that many accidents in so few days.
Like as not down to tailgating not leaving time to cope with soemthing that happens ahead.