ROC[nk] - family shelter

I suspect that this is actually an american utility design, not a British one, probably from the 1950/60s.
The British had had a lot of experience in designing air raid shelters during / after WW2, such as you don't put resources under floors and you need padded seating / beds.
Although this does have several redeeming features, I can see a number of actual & potential drawbacks, such as no second exit ...
Compare with the design of the ROC monitoring posts ... which had some similar drawbacks.
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not my image : fair use & public education