Sorry but “in this case there should have been a severe speed limit imposed as the points had a stretcher missing” is quite frankly wrong - the track should not have been used as a stretcher was missing - and should only have been returned to service once the track was correctly installed. Derailment was not due to the speed - even at low speeds the train would have derailed due to the effective gauge reduction.

In Ufton Nervet the situation was not helped by half-barriers although even full barriers would not stop anyone intent on suicide.

Given the number of people that stand on a train how do you restrain them - or do you limit the capacity of the train?

Not against seatbelts or properly stowed luggage but it could severly restrict the walk-on nature of the railways if people had to ‘belt up’.