WordNet (r) 3.0 (2006):

side road
    n 1: a minor road branching off of a main road

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "side road":
   back door, back road, back stairs, back street, back way, by-lane,
   bypass, bypath, byroad, bystreet, byway, departure, detour,
   deviation, digression, discursion, episode, excursion, excursus,
   roundabout way, side door, side path, side street, sidetrack