Take a look at your family to find someone who is at least 6ft tall. If you don't have such a person, have a chat with your neighbors and promise them a slice of home-baked cake if they lend you theirs.
Once you have this 6ft tall person, ask them to walk up and down the sidewalk that's outside your house. Pffft, easy, right? However, the rule is, they have to actually stay on the sidewalk and not duck or weave. If they can, hooray, you win! But if they have to lower their head or sidestep or twist because of some branch from a tree that's alongside? Bzzzt! It's time to trim those low-hanging branches!
(See https://www.pcva.org/pcva-news/sidewalk-safety-and-tree-limbs for the full details.)