49 C.F.R. Subpart B—Automatic Block Signal Systems
Title 49 - Transportation
The control circuits for home signal aspects with indications more favorable than “proceed at restricted speed” shall be controlled automatically by track circuits extending through the entire block. Signal governing movements over hand-operated switch in the facing direction shall display its most restrictive aspect when the points are open one-fourth inch or more and, in the trailing direction, three-eighths inch or more, except that where a separate aspect is displayed for facing movements over the switch in the normal and in the reverse position, the signal shall display its most restrictive aspect when the switch points are open one-fourth inch or more from either the normal or reverse position. At hand-operated crossover between main tracks, protection shall be provided by one of the following: (a) An arrangement of one or more track circuits and switch circuit controllers, (b) Facing point locks on both switches of the crossover, with both locks operated by a single lever, or (c) Electric locking of the switches of the crossover. Signals governing movements over either switch shall display their most restrictive aspect when any of the following conditions exist: (1) Where protection is provided by one or more track circuits and switch circuit controllers, and either switch is open or the crossover is occupied by a train, locomotive or car in such a manner as to foul the main track. It shall not be a violation of this requirement where the presence of sand, rust, dirt, grease or other foreign matter on the rail prevents effective shunting; (2) Where facing point locks with a single lever are provided, and either switch is unlocked; (3) Where the switches are electrically locked, before the electric locking releases. On track signaled for movements in both directions, a train shall cause one or more opposing signals immediately ahead of it to display the most restrictive aspect, the indication of which shall be not more favorable than “proceed at restricted speed.” Signals shall be so arranged and controlled that if opposing trains can simultaneously pass signals displaying proceed aspects and the next signal in advance of each such signal then displays an aspect requiring a stop, or its most restrictive aspect, the distance between opposing signals displaying such aspects shall be not less than the aggregate of the stopping distances for movements in each direction. Where such opposing signals are spaced stopping distance apart for movements in one direction only, signals arranged to display restrictive aspects shall be provided in approach to at least one of the signals. Where such opposing signals are spaced less than stopping distance apart for movements in one direction, signals arranged to display restrictive aspects shall be provided in approach to both such signals. In absolute permissive block signaling, when a train passes a head block signal, it shall cause the opposing head block signal to display an aspect with an indication not more favorable than “stop.” [33 FR 19684, Dec. 25, 1968, as amended at 49 FR 3384, Jan. 26, 1984] The circuits shall be so installed that each signal governing train movements into a block will display its most restrictive aspect when any of the following conditions obtain within the block: (a) Occupancy by a train, locomotive, or car, (b) When points of a switch are not closed in proper position, (c) When an independently operated fouling point derail equipped with switch circuit controller is not in derailing position, (d) When a track relay is in de-energized position or a device which functions as a track relay is in its most restrictive state; or when signal control circuit is deenergized. [33 FR 19684, Dec. 25, 1968, as amended at 49 FR 3385, Jan. 26, 1984] The battery or power supply for each signal control relay circuit, where an open-wire circuit or a common return circuit is used, shall be located at the end of the circuit farthest from the relay. Electric lock on hand-operated switch shall be controlled so that it cannot be unlocked until control circuits of signals governing movements over such switch have been opened. Approach or time locking shall be provided. [49 FR 3385, Jan. 26, 1984]
Title 49: Transportation
PART 236—RULES, STANDARDS, AND INSTRUCTIONS GOVERNING THE INSTALLATION, INSPECTION, MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES
Subpart B—Automatic Block Signal Systems
Standards
§ 236.201 Track-circuit control of signals.
§ 236.202 Signal governing movements over hand-operated switch.
§ 236.203 Hand operated crossover between main tracks; protection.
§ 236.204 Track signaled for movements in both directions, requirements.
§ 236.205 Signal control circuits; requirements.
§ 236.206 Battery or power supply with respect to relay; location.
§ 236.207 Electric lock on hand-operated switch; control.
