(a) The area embraced within the prolongation or connection of the lateral curb lines, or, if none, then the lateral boundary lines of the roadways of two highways which join one another at, or approximately at, right angles or the area within which vehicles traveling upon different roadways joining at any other angle may come in conflict.
     (b) Where a highway includes two roadways 40 feet or more apart, then every crossing of each roadway of such divided highway by an intersecting highway shall be regarded as a separate intersection.
     (c) The junction of an alley with a street or highway does not constitute an intersection.