Nearly all shared use trails alongside highways in Prince William County are maintained by the Virginia Department of Transportation (VDOT). That state agency has a report a problem website.
Expect no help in clearing snow, however. The agency says “VDOT does not remove snow from sidewalks or trails, rather, it concentrates on the roads. In some cases, local ordinances mandate property owners, which includes residents and businesses, must clear the snow from sidewalks.” For more., see this Active Prince William blog post, Pedestrian Access Issues Come to the Forefront at Prince William County Snowzilla Response Meeting.
Within Prince William County, contact 311 to report other trails that need a problem to be fixed.
In Manassas Park, drop a pin on the map.
City of Manassas has a trail repair section and a separate sidewalk repair form in Manassas Connect.