16. Circuitry

16.1 Warning Time

16.1.1 The time during which the warning system must operate, before the arrival of railway equipment at the crossing surface, must be the greatest of:

  1. 20 seconds, unless the grade crossing clearance distance (Figure 10-1) is more than 11 m (35 ft), in which case, the 20 seconds must be increased by one second for each additional 3 m (10 ft), or fraction thereof;
  2. the Departure Time for the design vehicle (article 10.3.2);
  3. the Departure Time for pedestrians, cyclists, and persons using assistive devices (article 10.3.3);
  4. the gate arm clearance time, plus the time to complete the gate arm descent, plus 5 seconds;
  5. the minimum warning time required for traffic signal interconnection as referred to in article 19.3(a);
  6. the time for the design vehicle to travel from the stopping sight distance, and pass completely through the clearance distance.

16.2 Consistency of Warning Times

16.2.1 Operating control circuits must provide consistent warning times for railway equipment regularly operating over the grade crossing.

16.2.2 Where the maximum railway operating speed has been reduced, the approach warning times for railway equipment regularly operating over the grade crossing, must not be more than 13 seconds longer than the warning time for the railway design speed.

16.3 Cut-Outs

16.3.1  Where railway equipment regularly stops, or railway equipment is left standing, within the activating limits of a warning system, the warning system must be equipped with a control feature to minimize the operation of the warning system.

16.3.2 A switch, when equipped with a switch circuit controller connected to the point and interconnected with the warning system circuitry, must cut out only when the switch point is within one-half inch of full reverse position.

16.4 Directional Stick Circuits

16.4.1 Where a warning system is equipped with directional stick circuits, the circuit must:

  1. include a stick release timer to activate the warning system after a preset time if there is failure of an approach circuit; or
  2. cause a train control signal system to restrict railway equipment speed to 25 km/h (15 mph) or less.

16.5 Identification

16.5.1  Each wire in all housings, including switch circuit controllers and terminal or junction boxes, must be identified at each terminal and the identification must not interfere with moving parts of the warning system.  Material used for identification purposes must be made of insulating material.  This requirement does not apply to light units or wiring that is an integral part of solid state equipment.

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