1a) "Bruchstücke [Subjekt] treiben den Hügel [Akk-Objekt] hinab", so they cases are nominative and accusative. For the second, "den" alone is enough to say it must be accusative. b) im Asphalt = in dem Asphalt, so it's dative 2) It's transitive. Just look it up: http://de.pons.com/%C3%BCbersetzung?q=hinabtreiben&l=deen&in=&lf=de ("hinabtreiben" is not there, but "hinauftreiben" and "hinaustreiben" follow the same construction). 3) It's Plusquamperfekt. The Vorgangspassiv would be "wurden hinabgetrieben" or "sind/waren hinabgetrieben worden", and the Zustandspassiv wouldn't take an accusative object.