I've worked for municipal tree depts. before. If they're public trees then there is an agency somewhere that has jurisdiction over them. If you cut them, they will come after you. There is a right way and a wrong way to trim trees and tree wardens do not like citizens taking matters into their own hands.

That said, if you find out the agency they will usually be glad to trim them for you if it will not harm the tree. Although trimming a tree so an adult can ride their bike on the sidewalk may not be a top priority.