Think it through. There's a safety gap of sorts alongside the central divide. It's only half a lane wide, but it's there and will normally be empty. (Edit > Watched again it's almost a full lane wide, over 6ft anyway.)
Although it would be nerve - wracking, a very safe option would be to stand 'upstream' of the crashed car. Alternatively, go 'downstream' but leave a lot of room so that if your car is hit you will be out of harm's way. Either of these would have seen the occupants completely unharmed in this case. I would have chosen either of those options in a heartbeat rather than stay in a car sticking out like that (and near a bend to boot.)
Re keeping doors locked, that advice is given here too, but mainly aimed at women in fear of being attacked. I think it's very poor advice, it simply doesn't put the relative risks in perspective.
But if you're going to stay in the car, at least keep seat belts on, the boy and mother clearly hadn't because they were thrown out. Thank god it worked out as well as it did for them.
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