Traffic Signal Preemption at Intersections Near Highway–Rail Grade Crossings (2017) / Chapter Skim
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Pages 31-38
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31 chapter seven CASE EXAMPLES PORTLAND, OREGON CASE EXAMPLE This case example highlights both the complexities of preemption near highway–rail grade crossings and state of the art approaches to addressing variability in both train speeds and actual right-of-way transfer time. The study site is atypical (with unique geometry and both heavy and light rail running through the crossing)
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32 FIGURE 16 Portland, Oregon, case example site. Source: Kittelson & Associates, Inc.
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33 green interval, TTG only shortens phases the amount needed to achieve TCGI at the design time or sooner. The preempt trap is prevented using a two-output strategy (RO1 and RO3 in the case of Portland)
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34 railway to generate a gate-down output in case the gate-down event does not occur (i.e., broken gate)
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35 FIGURE 19 Statistical distribution of railway outputs relative to train arrival at crossing. Source: Adapted from Moore et al.
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36 FIGURE 19 (Continued)
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37 OHIO CASE EXAMPLE In 2008, ODOT and the Ohio Rail Development Commission began engaging stakeholders (railway and traffic agencies) when upgrading its guidance regarding preemption of traffic signals near signalized intersections.
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38 A second type of second-train-coming event occurs when the first preempt event is ending and the gates are rising, and a second preempt event starts the gates back down before the first preempt is complete; gates going up (incompletely) and down is difficult for drivers.
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