As ninfan said, unadopted roads are a complicated subject, and TBF depending on the question I may not be particularly useful.
So OP; is the route in question definitely an public highway but being obstructed / encroached upon, or is it a private track but has a Public Right of Way along it, or is it a private track with no public access but people use it anyway?
Your Authority will have an online map (which might save you a trip) possibly with both ‘PROW’ and ‘adopted roads’ layers to double-check.
[edit]
towzer beat me to it. And of course it could be a private track, no public access, but some people may have rights to use it.