I have also seen the Cotton polos with "police" on the back. I feel like it is acceptable riding attire for a cop. All i have seen have been on trek or fuji mtbs normally in the 400-500 range. It is my understanding that the ride them because they may need to go offroad to catch whomever they chase. A road bike would not do.

I normally see alot at the jersey shore on the boardwalk, which is nice and handy. As prviously mentioned events like parades and sports events are another great use. They have also been out during charity bike events helping stop traffic and whatnot, very helpful.