6.12.5 Railway Level Crossings
If a road traffic signal installation is located in close proximity to a railway level crossing, there is a probability that:
- vehicle queues from a road traffic signal may extend across adjacent rail tracks
- vehicle queues from a railway level crossing may extend into nearby signalised intersections.
During such occurrences, special provision may be required to implement a phase to clear or limit queuing issues. This may be accomplished through interlinking a road traffic signal with railway level crossing controls.
Queue detection (Section 6.8.8) may be used to identify the presence of vehicle queues near a crossing. This may be required to ensure that:
- queues generated by a traffic signal do not extend across railway tracks
- queues resulting from level crossing operation will not interfere with traffic movements at the road intersection.
In order to detect an approaching train, an interface must be established between a road intersection traffic signal and adjacent railway level crossing control. A train must be detected at a time in advance of its arrival at a level crossing. This advance time period is determined to ensure that a traffic signal is able to respond to a train demand and be in a state which is satisfactory for level crossing operation when a train approaches a level crossing.
The advance time period required to detect a train is dependent on the worst possible phasing sequence at a site. This should consider:
- the worst scenario for terminating a running phase, which occurs when a train is detected immediately after a running phase has initiated and cannot be terminated until its safe minimum time has been satisfied (typically the worst case would be due to pedestrian movements)
- time required to clear queued vehicles, which is dependent on the queue length between the intersection stop line and a level crossing (during different times, days and considering any unusual patterns) and needs to consider the vehicle types comprising a queue (e.g. a B‑double would take considerably longer to clear than a car)
- boom gate delay (time between level crossing warning lights beginning to flash and when boom gates commence descending)
- time required for a vehicle to clear an intersection conflict zone and pass the level crossing before the warning lights start to flash (generally, the worst case time will be for a right turn filter vehicle, but the time may also depend on vehicle type).
The diagram shown in Figure 6.24 depicts these time periods. The advance time period required to detect a train is referred to as the train demand response time in the figure.
Source: Roads and Traffic Authority NSW (2010a).
Establishing the advance time period required to detect a train will aid in determining how far in advance of a level crossing train detection devices need to be positioned. Detection and other signal requirements should be determined in consultation with the appropriate railway authority.
Appendix I.1 presents an example of traffic signal phasing, timing and detection at a signalised intersection interfaced with a level crossing.
For further guidance on traffic detection and interlinking control at railway level crossings, refer to Institute of Transportation Engineers (2006), Roads and Traffic Authority NSW (2008b, 2010a, 2010b) and VicRoads (2014). General guidance on traffic management at railway level crossings is provided in Part 6 of the Guide to Traffic Management (Austroads 2019c). For information on signal displays, signs and markings at or near railway level crossings, refer to Part 10 of the Guide to Traffic Management (Austroads 2019d).