Passau is a Baverian city at the border of Germany and Austria and location, where the rivers Donau, Inn and Ilz unit.
In direction East and West on A3
Best spot to catch a ride is Donautal motorway petrol station, where you can either in direction Austria (East) or Germany (West). This petrol station is located on A3 just outside of Passau. It can be reached by catching Bus Nr. 10 in direction Schladringen r.d.D., which starts at the Central Bus Station in the city center of Passau. Be sure, you take the Bus to Schlading r.d.D. and not to Schladingen l.d.D., because the later will drop you on the wrong side of the river. Get of at Hoffeldweg and follow the road for another 100 meters. You should be directly below the autobahn bridge. Take a left on the street, which goes up the hill directly under the bridge until the road splits. If you want to hitch-hike in direction West, you should take the left road and you will get to Donautal Ost petrol station. If you want to catch a ride in direction East, take the right road and you will get to Donautal West petrol station. It should be quite easy to find a ride in either direction.