Section 2: Preempted Traffic SignalsAnchor: #i999539
Maintenance and Operations
Various settings in the traffic signal controller must be verified for compliance with the operation of the traffic signal controller and the preemption form (TxDOT Form 2304) for which the circuit was designed. The following procedures must be used when inspecting a traffic signal for preemption:
- Ensure controller delay time matches what is shown on preemption form (line 1).
- If delay time is used, ensure memory is set to non-locking so the controller does not accept false calls from the railroad company.
- Ensure minimum green time during preemption right-of-way transfer matches what is shown on preemption form (line 5).
- Ensure yellow change and red clearance times during preemption right-of-way transfer, after track clearance green, and after transition out of preemption, are not less than what is programmed for normal operation of the signal for any phase (when signal is not under preemption) per Section 4D.27 of the TMUTCD.
- Ensure yellow change and red clearance times during preemption right-of-way transfer match what is shown on the preemption form (lines 7 and 8).
- Ensure pedestrian walk time matches preemption form (line 11).
- Ensure pedestrian clearance time matches preemption form (line 12).
- Ensure track clearance green time matches what is shown on preemption form (line 51).
- Ensure track clearance, dwell/limited cycle, and exit phases are programmed properly in the controller.
- If a train passes through the crossing, verify that track clearance green does not terminate prior to the gates going down.
- If the gate-down circuit is used and a train passes through crossing, confirm that track clearance green terminates when gates go down and gate down preempt becomes active.
- Document any changes made to signal timings in the logbook in the traffic signal controller.
- Ensure preemption form and traffic signal layout design sheets are available in the cabinet.
- Ensure a warning label is present in the housing indicating the presence of the interconnection and that the cabling shall not be tampered or disconnected.
- Ensure battery back-up system is connected and functioning properly.
- Ensure interconnection conductor and conduit are functional.
Railroad companies are required to test preemption circuits on a monthly basis. Although the District Railroad Coordinator would not typically be present with the railroad company to verify that advanced preemption time is correctly functioning from the railroad company, the timing settings in the controller should be verified from time to time to verify the preemption is functioning as designed on the preemption form.Anchor: #i999636
Traffic Signal Design Changes
Another common concern involves when traffic signal timing modifications are made due to changes in speed limits or lane configurations. Ultimately, if changes are made, the yellow change and red clearance times during preemption cannot be less than what is programmed for normal operation of the signal for any phase. If the yellow change and red clearance times increase under normal operation, the times must also increase under preemption and other time during preemption must be sacrificed. This could typically occur by reducing delay time, minimum green time during right-of-way transfer, pedestrian timing during right-of-way transfer, or separation time, and would require that the preemption form be updated by the District Railroad Coordinator.
If a traffic signal is upgraded to accommodate pedestrian movements, the preemption setup should also be evaluated to see if pedestrians should be considered during preemption.
Finally, any changes to a roadway intersection adjacent to a railroad crossing should be coordinated with the affected railroad company. This includes if all work is performed off of railroad right-of-way to ensure there are no traffic impacts to the railroad crossing or preemption setup.