Answer:
A Right of Way is a grant to cross the property of another for access to your land.
The dimensions of a Right of Way are generally set forth in the instrument that created the ROW. You need to check the language in your deed or perform research in the land records to locate the original grant. Sometimes the grant will simply state the ROW is "as now exists" or "as commonly used". In that case the evidence would be on the ground over the visible travelled way.
Ancient ROWs are often described for use as "for teams to travel" or a "cart path". If it was created only wide enough for teams to travel it wasn't very wide. Ancient ROWs are often very narrow. Again, there should be evidence of the width on the ground if not recited in the deed.