It's happened. Albeit not on a motorway but on a very busy 3 lane dual carriageway where there was a hard shoulder.
Got the kids out the car, up the side and behind the crash barrier. Stuck the red warning triangle about 10 cars length behind the car whilst OH was calling the breakdown and police. Police turned up within minutes and dealt with the traffic.
Even standing in relative sanctuary well away from danger, the speed the traffic was whizzing past was scary. I really felt for the RAC man.