At grade crossings, there are typically two types of potential queues, influence zone queues and gate spill back queues as illustrated in Figure 2-1. Both types of queues should be considered when determining the need for preemption.

The Requestor shall measure the Clear Storage Distance (CSD) as defined in TxDOT Form 2304-I and illustrated above. TXDOT prefers on-site measurements however the distance can be estimated via a desktop survey using reliable aerial imagery or design documents.