As a side note, "highway" by the states definition includes all route roads, so in addition to 91, 95, 15/merritt/wilbur, 9, 8, 324, etc, it will also include 34, 68, 17, 80, etc.
Route roads also have other names and will often go right through the center of towns, so don\'t think this means as long as you\'re not on 95 you\'re safe.
Also, even numbers go east west and odd numbers go north south.