Traffc signal operations near highway—rail grade crossings are important from both safety and mobility perspectives, but practice varies widely. The goal of this synthesis is to document the state of practice of traffic signal preemption deployed at intersections adjacent to highway—rail grade crossings in the United States and Canada. Specific objectives include: • Learning what practices have been used; • Identifying ongoing and recently completed research; and • Learning what problems remain largely unsolved. Methodology for compiling information for this synthesis included a literature search, a survey of U.S. state and Canadian provincial departments of transportation, and the completion of three case studies (Portland, Oregon, and the states of Ohio and California) to determine additional lessons learned, innovations, and gaps in practice. Forty of 49 states and one of three Canadian provinces responded to an e-mailed survey request; in addition, four Canadian provinces not included in the original survey distribution offered information (Figure 1). Hawaii was not included in the survey because the state has no operating freight or passenger railroads system, and the one United States territory queried did not respond. The most important conclusion from this synthesis, described in more detail in chapter eight: Conclusions and Suggestions for Further Research, is that the state of the practice does not adequately reflect current state-of-the-art capabilities. Although some highway and railway agencies use advanced capabilities demonstrated in the case examples, the majority of surveyed agencies (55%) uses a simple, two-wire preempt at their highway—rail grade crossings; and of those agencies using two-wire preempt, 58% use normally closed circuits. This two-wire preempt circuit conveys no more information to the traffic signal controller than was available when track circuits were first used to preempt traffic signals. Railway agencies are regulated by FRA, which governs railway-equipment aspects of crossings. While FRA encourages railway and highway agencies to coordinate joint inspections to verify that railway crossing warning systems interconnected to traffic signals function properly, the survey indicates that few highway agencies coordinate inspections with railway agencies. There are several opportunities that could lead to improved safety and operation of highway—rail grade crossings. Issues that could be considered, also detailed in chapter eight, include identification and review of key limitations and conflicts in current operations; clear definitions of terms and operational concepts; use of multiple signals and preempts; coordination with railway agencies; agency employee and contractor training; and inspections and performance measures. Development of guidelines for optimal traffic signal operation would also be helpful. (Author/publisher)
Samenvatting