SAFE HAVEN  WW2 etc

Public air raid shelters had (during world war I and II) at best a mixed reputation, with their flimsy construction contributing to the general unease at using them.
This was compounded by a series of incidents where badly constructed shelters collapsed in on their unlucky occupants after nearby blasts, 

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The difference between Anderson and Morrison air raid shelters during the Second World War | Blog | Findmypast.co.uk 

In World war One, there were underground bunkers complexes housing command posts, hospitals, etc.
These had more than one exit and at least some of these exits were located in areas with no other structures, so there would be no rubble.

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In World War Two, smaller bunkers either exited in a trench or had an exit that was a building standing clear above ground.

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World War Two air raid shelters consisted of vast bunkers with various exits.

Basements were often converted in makeshift shelter complexes.
The walls between the various basements of houses were knocked through so you could basically enter any basement and its exit in a city block.

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Small bunkers used the same principles as earlier ones, although some also had a hatch on top that was located a point that could not be blocked by rubble.

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Exits of Cold War bunkers were often disguised so as to prevent unauthorized personnel from gaining access.

They could be disguised as a service tunnel in the metro/sewers, as a hatch near a lock in a port, or just as a door in a street.

These lasts ones would consist of steel-reinforced above-ground exits, pretty much like those of World War Two but disguised as an ordinary street door.

(5) How do people escape from an underground bunker if it's been covered in rubble? - Quora 

MOVING TO THE NUCLEAR AGE.

there is a landslide of differences and additional challenges.

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