Back in the 70's when I was a Detroit cop it was mandatory we had to wear our police hats even in the police cars. Back then there was no air conditioning in those cars. We would get a written reprimand if caught not having our hats on even if we were in a foot chase or fighting with a perp and our hats came off. There was a unit that would follow officers around just to see if they had their hats on. We would call them "The Hat Squad" plus a few other names!