The Middle Rhine Valley has excellent rail access. The left-bank Koblenz-Mainz line (served by regional trains) stops at Boppard, Boppard Hbf, St. Goar, Oberwesel, and Bacharach. The right-bank line serves St. Goarshausen and the towns opposite. Trains run roughly every 30 minutes in each direction. Koblenz at the northern end and Mainz at the southern end are the main connections to the national network, including high-speed trains from Frankfurt (30 minutes to Mainz).
By car, the B9 runs along the left bank and the B42 along the right bank. Neither road is fast — the valley is narrow and the towns are frequent — which suits the pace of exploring the valley.
Frankfurt am Main airport is the practical entry point: Mainz is 30 minutes by regional train, Koblenz about 75 minutes.