15.1 The operation of traffic signals on a road approach shall be preempted by a grade crossing warning system: 

(a) where there is less than 60 m between the stop line for the traffic signals and the rail nearest the road intersection; or 

(b) if it has been determined that traffic queued for the traffic signals regularly encroaches closer than 2.4 m to the rail nearest the road intersection. 

15.2 Except where otherwise specified in this standard, the preemption of traffic signal operation by a grade crossing warning system shall be designed and operate in accordance with the ITE Preemption Practices and the AREMA Communications and Signals Manual. 

15.3 The preemption of traffic signal operation by a grade crossing warning system shall: 

(a) provide sufficient time to clear the grade crossing of road traffic before the train's arrival at the grade crossing; 

(b) prevent movement of road traffic from the intersection towards the grade crossing.