Chapter 10D. Highway-Light Rail Transit Active Traffic Control Grade Crossing SystemsSection 10D.01 IntroductionSupport: Guidance: If a pedestrian route is provided, sufficient clearance from supports, posts, and gate mechanisms should be maintained for pedestrian travel. Option: Support: When light rail transit speed is cited in this Part, it refers to the maximum speed at which light rail transit vehicles are permitted to traverse a particular grade crossing. Section 10D.02 Flashing-Light SignalsSupport: Standard: Guidance: Option: Section 10D.03 Automatic GatesSupport: Guidance: Option: Traffic control signals may be used instead of automatic gates at highway-light rail transit grade crossings within highway-highway intersections where light rail transit speeds do not exceed 60 km/h (35 mph). Traffic control signals or flashing-light signals without automatic gates may be used where the crossing is at a location other than an intersection and where light rail transit speeds do not exceed 40 km/h (25 mph) and the roadway is a low-volume street where prevailing speeds do not exceed 40 km/h (25 mph). Automatic gates may be supplemented by cantilevered flashing-light signals (see Figure 8D-1) where there is a need for additional emphasis or better visibility. The effectiveness of gates may be enhanced by the use of channelizing devices or raised median islands to discourage driving around lowered automatic gates. Section 10D.04 Four-Quadrant Gate SystemsOption: Standard: The Four-Quadrant Gate system shall consist of a drive mechanism and fully retroreflectorized red- and white-striped gate arms with lights, and which in the down position extends individually across the entrance and exit lanes of highway traffic as shown in Figure 8D-2. Standards contained in Section 10D.02 for flashing-light signals shall be followed for signal specifications, location, and clearance distances. In the normal sequence of operation, unless constant warning time or other advanced system requires otherwise, the flashing-light signals and the lights on the gate arms (in their normal upright positions) shall be activated immediately upon detection of the approaching light rail transit vehicle. The gate arms for the entrance lanes of traffic shall start their downward motion not less than 3 seconds after the flashing-light signals start to operate and shall reach their horizontal position at least 5 seconds before the arrival of the light rail transit vehicle. Exit gate arm activation and downward motion shall be based on timing requirements established by an engineering study of the individual site. The gate arms shall remain in the down position as long as the light rail transit vehicle occupies the highway-light rail transit crossing. When the light rail transit vehicle clears the highway-light rail transit grade crossing, and if no other light rail transit vehicle is detected, the gate arms shall ascend to their upright positions, following which the flashing lights and the lights on the gate arms shall cease operation. Gate arm design, colors, and lighting requirements shall be in accordance with the Standards contained in Section 8D.04. Except as noted in the Option below, the exit gate arms shall be designed to fail-safe in the up position. At locations where gate arms are offset a sufficient distance for vehicles to drive between the entrance and exit gate arms, median islands shall be installed in accordance with the needs established by an engineering study. Guidance: Four-Quadrant Gate systems should only be used in locations with constant-warning-time light rail transit vehicle detection. The operating mode of the exit gates should be determined based upon an engineering study, with input from the affected transit agency. If the Timed Exit Gate Operating Mode is used, the engineering study, with input from the affected transit agency, should also determine the Exit Gate Clearance Time. If the Dynamic Exit Gate Operating Mode is used, vehicle intrusion detection devices should be installed to control exit gate operation based on vehicle presence within the minimum track clearance distance. Regardless of which exit gate operating mode is used, the Exit Gate Clearance Time (see Section 8A.01) should be considered when determining additional time requirements for the Minimum Warning Time. If a Four-Quadrant Gate system is used at a location that is adjacent to an intersection that could cause vehicles to queue within the minimum track clearance distance, the Dynamic Exit Gate Operating Mode should be used unless an engineering study indicates otherwise. If a Four-Quadrant Gate system is interconnected with a highway traffic signal, backup or standby power should be considered for the highway traffic signal. Also, circuitry should be installed to prevent the highway traffic signal from leaving the track clearance green interval until all of the gates are lowered. At locations where sufficient space is available, exit gates should be set back from the track a distance that provides a safety zone long enough to accommodate at least one design vehicle between the exit gate and the nearest rail. Four-Quadrant Gate systems should include remote health (status) monitoring capable of automatically notifying light rail transit signal maintenance personnel when anomalies have occurred within the system. Option: Four-Quadrant Gate system installations may include median islands between opposing lanes on an approach to a highway-light rail transit grade crossing. Guidance: Section 10D.05 Traffic Control SignalsSupport: Standard: Guidance: Coordination with the flashing-light signal system should be considered for traffic control signals located more than 60 m (200 ft) from the crossing. Factors to be considered should include traffic volumes, vehicle mix, vehicle and light rail transit approach speeds, frequency of light rail transit vehicles, and queue lengths. If the highway traffic signal has emergency vehicle preemption capability, it should be coordinated with light rail transit operation. Where light rail transit operates in a wide median, vehicles crossing the tracks and being controlled by both near and far side traffic signal faces should receive a protected left-turn green phase from the far side signal face to clear vehicles from the crossing when light rail transit vehicles are approaching the crossing. Option: Traffic control signals may be installed in addition to four-quadrant gate systems and automatic gates at a highway-light rail transit crossing if the crossing occurs within a highway-highway intersection and if the traffic control signals meet the warrants described in Chapter 4C. At a location other than an intersection, when light rail transit speeds are less than 40 km/h (25 mph), traffic control signals alone may be used to control road users at highway-light rail transit grade crossings only when justified by an engineering study. Typical circumstances may include:
Support: Section 10D.06 Highway Traffic Signal Preemption Turning RestrictionsGuidance: Standard: Guidance: Support: Option: Standard: Section 10D.07 Use of Traffic Control Signals for Control of Light Rail Transit Vehicles at Grade CrossingsGuidance: Support: Figure 10D-1 Examples of Light Rail Transit Signals Option: Standard: If the light rail transit crossing control is separate from the intersection control, the two shall be interconnected. The light rail phase shall not be terminated until after the light rail transit vehicle has cleared the crossing. Option: Guidance: Section 10D.08 Pedestrian and Bicycle Signals and CrossingsStandard: Guidance: Flashing-light signals (see Figure 10D-2) with a Crossbuck (R15-1) sign should be installed at pedestrian and bicycle crossings where an engineering study has determined that the sight distance is not sufficient for pedestrians and bicyclists to complete their crossing prior to the arrival of the light rail transit vehicle at the crossing, or where light rail transit speeds exceed 60 km/h (35 mph). If an engineering study shows that flashing-light signals alone would not provide sufficient notice of an approaching light rail transit vehicle, the LOOK (R15-8) sign (see Figure 10D-2) and/or pedestrian gates should be considered (see Figures 10D-3, 10D-4, and 10D-5). Figure 10D-2 Example of Light Rail Transit Flashing-Light Signal Assembly for Pedestrian Crossings Figure 10D-3 Example of Pedestrian Gate Placement Behind the Sidewalk Figure 10D-4 Example of Pedestrian Gate Placement with Pedestrian Gate Arm Figure 10D-5 Examples of Placement of Pedestrian Gates Support: The swing gate alerts pedestrians to the light rail transit tracks that are to be crossed. Swing gates are designed to open away from the tracks, requiring users to pull the gate open to cross, but permitting a quick exit from the trackway, and to automatically close. Option: Figure 10D-6 Example of Swing Gates Pedestrian barriers at offset crossings may be used at pedestrian and bicycle crossings as passive devices that force users to face approaching light rail transit before entering the trackway (see Figures 10D-7 and 10D-8). Figure 10D-7 Example of Pedestrian Barriers at an Offset Highway-Light Rail Transit Crossing Figure 10D-8 Examples of Pedestrian Barrier Installation at an Offset Nonintersection Light Rail Transit Crossing |