Fridays are just total SH1T for driving anywhere, regardless of broken-down vehicles. It doesn't matter what's broken down, to be honest - I mostly see stranded car drivers far more than caravans (which generally are off the roads from October through to early March) or even lorries. I'd say take all heavy goods off the roads during daylight on Fridays to ease congestion, although for decades I preferred the once common European rule of taking them off during daylight, full stop, having them drive by night, to offload their deliveries early a.m.
We'd still be better off with deregulated motorways (another soapbox of mine), with the left lane up to 70 mph, the middle from 70 mph to infinity, and the right for overtaking the lot, but not hogging. There's this notion that speed kills, but what kills, actually (apart from the sudden stop) is stupidity or inexperience. I like the idea of introducing constraints on newly-licensed drivers (of any age) being put through a probationary period and not carrying passengers for, say, a year after qualifying. That'd help to stop the inane fatalities racked up by young lads showing off their Halfords Specials to their mates.