While watching last week's documentary on the collapse of the twin towers of the World Trade Centre (Horizon, BBC2, Thursday 7 March), it occurred to me that more people could have escaped from above the impact point had staircases been positioned in the corners of the buildings rather than at the cores.
Many of the people who died were trapped above the level of impact because the staircases in both buildings were cut - all of them in the first building to be struck and all but one in the second.
Based on the information in the documentary it appears likely that, had the staircases been positioned in the corners, at least two would have survived the impact in each building and possibly all four in the first building to be struck. This would have enabled more people to escape and saved many lives.
It is difficult to envisage an event that could have cut staircases in all four corners of these buildings at the same time. This idea appears to be worthy of consideration in the design of future tall buildings as a means of improving the occupants' chances of surviving such a situation.
Keith Mapp (M), 19 Oakhill Road, Horsham, West Sussex RH13 5SA