Pulowski Preservation shelter

Pulowski Preservation Shelters are coin-operated, one-person fallout shelters found on street corners throughout the more urban areas of the Capital Wasteland. People would ostensibly use them as a last-minute resort in the event of a nuclear attack; however, they have no food or water supplies and may not even have had recyclable air, so the customer would have to bring with them anything they thought they would need for survival (and due to the last-minute nature of the booth, most people did not bring very much with them to begin with). The instructions on the inside tell the occupant to "wait for the radiation levels to drop" before leaving.

The booths were obviously not very effective at all--every one found within the game contains a charred skeleton and a few items that the person brought in with them.

Though they're terrible for protecting people from nuclear attack, the preservation shelters are at least useful for hiding from enemies; at least one NPC in the game uses a Pulowski Shelter as such, in "Those!", and the player may also use them to hide, at least temporarily.

There is in fact a place near Georgetown, filled with cars and other destructibles were you can test the uselessness of these shelters. Blowing up a car there starts a chain reaction, doing tremendeous damage to the few super mutants in the area and will also kill you if you stay close. Going in the shelter however will save your live though you will suffer damage and even radiation from the blast.

So they were indeed not very "preservative"