The Requestor shall request all information related to the traffic signal timing from the Highway Authority as it is necessary to determine the Right-of-Way Transfer Time (RWTT) and complete TxDOT Form 2304. If a new traffic signal is being proposed, the proposed times to be programmed to the controller should be provided. The traffic signal timing data shall include, but may not be limited to, the overall cycle length, default minimum times, guaranteed maximum times, track clearance green or Preemption Clearance Interval, signal phasing, and transition during a preemption event, which includes the following (note these times may be different during preemption than the default minimum times, except as noted below):

Minimum Green Time
Yellow Change Time (shall not be shortened or omitted)
Red Clearance Time (shall not be shortened or omitted)
Pedestrian Walk Time
Pedestrian Clearance Time

The following parameters are defined by , AREMA and ITE and used to provide sufficient preemption time to the interconnected traffic signal prior to the arrival of a train at a crossing. The Requestor should understand these parameters when performing preemption calculations and the effect of signal timing on preemption to communicate preemption timing needs to the Railroad Authority.

Right-of-Way Transfer Time (RWTT)

is the amount of time needed prior to display of the track clearance interval. This includes any time needed by the railroad, light rail transit, or highway traffic signal control equipment to react to a preemption call, and any traffic control signal green, pedestrian walk and clearance if used, yellow change, and red clearance intervals for conflicting traffic.

Since preemption may occur at any given moment during normal operations, enough time must be provided to safely transition any active phases to the Preemption Clearance Interval. In order to terminate any active phase prior to track clearance green, the minimum green, yellow change, red clearance, and pedestrian clearance intervals must be considered. The RWTT values in TxDOT Form 2304 shall reflect the worst-case scenario.

TxDOT Form 2304-I provides general guidance to assist the Requestor when it may be appropriate to truncate the pedestrian clearance time in the presence of a preemption call at a crossing. Consideration to truncate the pedestrian time includes the following:

Pedestrian volumes
Frequency of preemption events
Vehicle minimum times
Intersection geometry
Types of pedestrian users

Limitations in railroad equipment may necessitate partial truncation of pedestrian clearance time at locations where the Highway Authority would otherwise desire full pedestrian clearance time. Details related to how to handle this scenario are discussed further in Chapter 4 of this manual.

Track Clearance Green (TCG)

is the portion of the traffic signal sequence when the RWTT has completed and green signal indications are displayed to roadway users to clear the MTCD. Per TxDOT Form 2304-I, the TCG is the time required to avoid the preempt trap and provide enough time for the design vehicle to clear the portion of the CSD as defined in the calculations. TCG should be equal or exceed the queue clearance time. TCG is the Preemption Clearance Interval (PCI) where a green indication is required to allow vehicles to clear the tracks.

Queue Clearance Time (QCT)

is the time required for the Design Vehicle stopped within the minimum track clearance distance to start up, move through and clear the MTCD. If pre-signals are present, this time should be long enough to allow the Design Vehicle to move through the intersection or clear the tracks if there is sufficient CSD. If a four-quadrant gate system is present, this time shall be long enough to permit the exit gate arm to lower after the Design Vehicle is clear of the MTCD.

Separation Time

is the component of maximum highway traffic signal preemption time during which the MTCD is clear of vehicular traffic prior to the arrival of the train.

Maximum Highway Traffic Signal Preemption Time

is the maximum amount of time needed following the initiation of the preemption sequence for the highway traffic signals to complete the timing of the RWTT, QCT, and Separation Time.