Complex sentence: Route 20A is located entirely within Springfield, Massachusetts, paralleling the section of U.S. Route 20 where U.S.20 runs concurrently with Interstate 291.
Split into simpler sentences: Route 20A is a state highway located entirely within Springfield, Massachusetts, United States. The route, an alternate route of U.S. Route 20, parallels the section of U.S.20 concurrent with Interstate 291.