This Manual Part recommends functional/operating guidelines for control of automatic grade crossing warning systems. Draft

Transcription

1 Recommended Functional/Operating Guidelines for Control of Automatic Grade Crossing Warning Systems Revised 2017 (6 Pages) A. Purpose This Manual Part recommends functional/operating guidelines for control of automatic grade crossing warning systems. B. Warning Devices For grade crossing warning devices, see Manual Part Recommended Functional/Operating Guidelines for Grade Crossing Warning Devices. C. General 1. Warning devices which indicate the approach of a train shall be so controlled that they will operate for a sufficient interval of time before the arrival of any train at the grade crossing. The interval of time should be determined conforming to Manual Part , Recommended Instructions for Determining Warning Time and Calculating Minimum Approach Distance for Grade Crossing Warning Systems or individual railroad requirements. 2. Warning device controls shall be designed using fail safe principles. The failure of any safety-critical component or system shall result in the operation of the warning devices. 3. Where means are provided for cutting out the warning devices during intervals when trains make regular operating stops or perform switching operations on approach circuits: a. Controls shall be designed to provide a reactivation of the warning devices before the train enters the crossing. b. Cutout features shall not bypass island circuits. c. Refer to Manual Part , Recommended Vital Circuit Design Guidelines for Reverse Switch Cutout Applications for Deactivating Grade Crossing Warning Devices, for some examples of cutout features. d. Devices which enable personnel authorized by the railroad to manually override the operation of automatic warning systems shall be labeled as to their intended function and track designation. - 1

2 Part Where manual supervisory control of warning devices is provided in addition to automatic controls: a. Automatic controls actuated by approaching trains other than that for which manual control has been made effective shall take precedence over the manual control. b. Means shall be provided to make certain that the controls are restored to automatic operation. c. Means shall be provided to prevent manual operation by unauthorized persons. 5. Where preemption of highway traffic signals is required, the interconnection shall be provided conforming to Manual Part , Recommended Functional/Operating Guidelines for Interconnection Between Highway Traffic Signals or other Traffic Control Devices and Grade Crossing Warning Systems. D. Controls for Grade Crossing Warning Devices 1. Operating time should be calculated in accordance with Manual Part , Recommended Instructions for Determining Warning Time and Calculating Minimum Approach Distance for Grade Crossing Warning Systems, or individual railroad requirements. 2. Warning devices shall operate until the rear of the train clears the crossing. 3. Where differing train speeds or train stops on a given track are encountered, consideration should be given to the installation of Constant Warning Time Devices or other means to achieve intended operation. 4. Flashing lights shall operate for the duration of the warning system activation, except as recommended in Manual Part , Adjacent Track Interconnected Grade Crossing Warning Systems. 5. Pedestrian bell or other audible warning device, if used without gates, shall sound for the duration of the warning system activation unless otherwise determined by the Diagnostic Team or ordered by a public agency. E. Controls for Two and Four Quadrant Automatic Gates 1. The lights on the flashing light signal shall operate any time a gate is in a position to obstruct traffic. - 2

3 2. Gate arm lights shall operate in conjunction with the flashing light signal, as follows: a. When a gate is in a position to obstruct roadway traffic, the lights shall operate at all times. b. The light nearest the tip of the gate shall be illuminated steadily. c. For roadway gates, at least two lights shall flash alternately and should flash in unison with the lights on the flashing light signal. 3. The entrance gate(s) shall start downward motion not less than 3 sec. after the flashing light signal starts to operate. 4. The exit gate(s) shall operate in one of the following modes of operation known as the EGOM (exit gate operating mode) as determined by the Diagnostic Team or ordered by a public agency: a. Dynamic EGOM A mode of operation where exit gate operation is based on presence of vehicles within MTCD. Dynamic mode should be used whenever traffic routinely backs up or stops on the crossing. Examples include, but are not limited to: Locations where there is an intersection beyond the crossing. Traffic operations that may cause vehicles to stop on the crossing. Bus stops in close proximity to the crossing. Driveways in close proximity to the crossing. (1) The exit gate(s) shall start downward motion after the vehicle detection system indicates no vehicles are located within the minimum track clearance distance (MTCD) and any (optional) exit gate clearance time (EGCT) has completed timing. Note that the entrance gate(s) and the exit gate(s) may start downward motion simultaneously if no vehicles are located within MTCD and EGCT is zero. Exit gate(s) should be individually controlled by each roadway approach. (2) Control circuitry should be employed to check the position of the entrance gate(s) to confirm they are lowered. In the event any entrance gate does not indicate it is lowered within a - 3

4 Part predetermined number of seconds after release, the associated exit gate(s) may be fully raised. This time interval should be the maximum expected operating time for the entrance gate(s) circuit to indicate that the gate has lowered. (3) Control circuitry shall be designed such that the detection of the train within the MTCD by the vehicle detection system does not cause exit gates to rise. (4) Where an island only circuit is used for one or more tracks, an EGCT period shall be provided prior to bypassing the vehicle detection system. (5) In the event the exit gate(s) are raising but not yet vertical and a second train is detected, the exit gates shall continue to raise if the vehicle detection system detects vehicle presence within MTCD. If no vehicles are detected, the exit gate(s) should reverse and begin to descend. (6) The vehicle detection system shall be based on fail-safe design principles and shall continuously perform a self-check operation to provide a health status output. In the event the vehicle detection system fails to properly self-check, the health output shall be set false with the exit gate(s) remaining in or returning to the raised position, or reverting to timed mode as described in 3b, below. b. Timed EGOM A mode of operation where exit gate operation is based on a predetermined time interval. This operating mode is typically used where traffic has an unrestricted path over the crossing or as a backup to Dynamic EGOM where approved by the public agency. (1) The exit gate(s) shall be designed to start downward motion a predetermined number of seconds after the entrance gate(s) start downward motion. Note that the entrance gate(s) may or may not be fully lowered at the time the exit gate(s) start downward motion. This timed value is known as the exit gate clearance time (EGCT). (2) Control circuitry shall be employed to check the position of the entrance gate(s) to confirm they reach the lowered position. In the event any entrance gate does not indicate it is lowered within a predetermined number of seconds after release, the corresponding exit gate(s) shall be raised, unless otherwise - 4

5 established by an engineering study of the individual site. This time interval should be based on the maximum expected operating time for the entrance gate(s) circuit to indicate that the gate has lowered. Once the entrance gate indicates that it has lowered, the exit gate should begin to lower. (3) Control circuitry shall be employed to check the position of the exit gate(s) to confirm they begin to raise prior to raising the corresponding entrance gate(s). In the event any exit gate fails to begin to raise, the corresponding entrance gate(s) shall remain lowered. 5. Entrance gate(s) shall reach the lowered position at least 5 sec. before arrival of a normal train movement and shall remain in that position until the rear of the train has cleared the crossing. 6. In timed mode, exit gate(s) shall be designed to reach the lowered position before arrival of a normal train movement. 7. In dynamic mode, exit gate(s) may reach the lowered position at the same or any time after the entrance gate is lowered. 8. Circuits shall be so arranged that a failure of the gate mechanism to operate as intended will not prevent the lights on the gate arm and the flashing light signal from operating on the approach of a train. 9. Circuits shall be designed such that flashing lights and gate arm lights shall continue to operate until all associated entrance and exit gate(s) are fully raised. 10. Pedestrian bell or other audible warning device shall sound for the duration of the warning system activation, except when gates are being raised, unless otherwise determined by the Diagnostic Team or ordered by a public agency. 11. Processor based control systems should include diagnostic capabilities to assist in testing, troubleshooting, and maintenance of the system. - 5