Definitions for "SIDEROAD"
An INTERSECTION of exactly three roads from which a road goes to the left or to the right but not both, and a road goes generally ahead.
An intersection of exactly three roads where a road goes generally ahead and another road goes to the left or to the right, but not both.
At an intersection of exactly two roads, one of which is generally ahead and the other of which is either to the left or to the right, but not both, the sideroad is the road that is either to the left or to the right.