I was a kid in the late '40s in New York City (the days of "duck and cover" in school). I remember seeing garbage trucks with the Civil Defence symbol on them and wondered what they had to do with Being Prepared.
Years later I learned that they were to be used to cart off the bodies of the A-bomb victims - that's how naive the times were.
‘Clean up’ after a neutron bomb would require just such ‘volume’ to cart off the rotting corpses.