49 CFR §236.514
Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
The automatic cab signal system shall be interconnected with the roadway-signal system so that the cab signal indication will not authorize operation of the train at a speed higher than that authorized by the indication of the roadway signal that governed the movement of a train into a block except when conditions affecting movement of trains in the block change after the train passes the signal.