A cable exit trough is mountable to a lateral trough section either during initial assembly of the cable routing system, or at a later date. The exit trough includes a bracket portion mountable to the top edge of one of the sides of the lateral trough section. Two lead-ins are provided to lead the cable in an upward direction from the lateral trough section to the exit trough. The exit trough includes an exit trough portion extending from the bracket portion upwardly away from the lateral trough section. The exit trough portion includes a convexly curved bottom trough surface, and two convexly curved upstanding sides. The exit trough portion and the lead-ins define a cable pathway from the lateral trough section to an exit point of the exit trough portion which can either lead downwardly relative to the lateral trough section, or horizontally.