The Requestor should compare the results of Steps 1 and 2. If the measured distance (Step 1) is less than the queue lengths calculated (Step 2), the diagnostic team should consider preemption.

If a traffic signal is warranted under Warrant 9 in Section 4C.10 of the TMUTCD or any other warrant and queueing is anticipated at the crossing and the highway authority elects to install a signal at the intersection, TxDOT Form 2304 shall be completed and provided to the District Railroad Coordinator prior to the diagnostic inspection. TxDOT Form 2304-I provides information to assist with the completion of the TxDOT Form 2304. Chapter 3 of this manual builds on TxDOT Form 2304-I by providing guidance on collecting data and special preemption scenarios affecting preemption calculations. At the diagnostic inspection, the diagnostic team will discuss the safety implications of installing a traffic signal near a crossing and the specific preemption needs as discussed later in this manual.

When gate spillback queuing is observed, it can often be mitigated with strategies such as vehicle detection, phase omissions, and turn restrictions. If the signal operations can be designed such that on-track queuing is prevented at all times during both normal and preemption operations, then there may not be a significant need for railroad interconnection to be implemented. The diagnostic team should evaluate and observe each grade crossing carefully to determine the best solution.