Firstly, in my experience of commuting up and down the M1 and in a previous existence the M25, I have seen many accidents, not one of which involved a caravan. Generally the [totally subjective] cause seems to be idiots in BMW's driving to a completely different set of rules to the rest of us. The sooner we issue the Police with ropes long enough to hang speeding drivers from the nearest lamp post the better.
Secondly, I feel there has been an element of blamimg 'pilot error' for this accident. Whilst in no way supporting the driver I suspect that the motorway engineer who designed the crash barriers allowing a gap big enough for any vehicle to pass through near such a major railway line, indeed any other road or railway line, has great difficulty sleeping.