Just attended a gathering of AT trail maintainers in the Berkshires. One issue discussed was the increasing use of ATVs on and near the trail. Just want to hear the perspective of hikers on this issue. Is it a serious problem? Have you seen ATVs riding of the AT? There are some state parks in Mass. in which ATVs are allowed, and ATV trails will cross the AT. But ATVers sometimes ignore or remove the 'foottravel only" signs at the trail crossings and ride on the trail itself, causing serious damage to the treadway.
By the way, the only place on the entire AT where snowmobiles are allowed is the Mass Pike overpass. That overpass is legally part of a snowmobile trail., but the snowmobile trail is officially closed in summer and there should be no ATV use there ever. But it happens. If you ever see ATVs riding on the trail, you could get their license number and report them.