A good depot design should always have at least two exits
Both Reading upper and lower depot's
do have two exits, but the shape of the upper depot (basically a triangle) means that a derailment in the wrong place will block off most of the rest of the sidings. I'm struggling to recall for definite but I think the new depot has three exit points (two from the outset and a third when the
IEP▸ part is completed), so that along with its elongated shape should mean that a derailment won't have quite the same implications in the future.