The signed mainline portion of CR 509 begins at a complex intersection in the town of Westfield, west of Elizabeth. State Route 28 (South Avenue) and Union County Route 610 (North Avenue) come from Scotch Plains to the west on either side of the train tracks running along New Jersey Transit's Raritan Valley Line and criss-cross at a traffic circle a few hundred feet from the Westfield Train Station. CR 509 (East Broad Street) branches off in a northeast direction from Route 28 just after the state highway branches off of the circle and crosses under the tracks before continuing east. From its southern terminus to Elmer Street in Westfield, the road is town maintained.