From Salzburg-Linz: A1 to Melk (Exit Wachau-Donaubrücke), afterwards around 30 km on B3 to Dürnstein
From the North of Vienna: A22 to Tulln, further S5 to Krems and than only 7 km on B3 to Dürnstein
From the West of Vienna: A1 until Exit St. Pölten Ost, further S33 to Krems and than only 7 km on B3 to Dürnstein
The city center of Dürnstein is a no-parking Zone for cars. You can park on 4 billable car pars outside. If you stay in Dürnstein or Loiben, you will get a ticket for free at your accomodation.
More information about Parking will you find here.
Weather you arrive from Krems or from Melk, the local busses drive every hour. Route planner: www.vor.at