49 C.F.R. § 236.804 Signal, block.
Title 49 - Transportation
A roadway signal operated either automatically or manually at the entrance to a block.
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 G—Definitions
§ 236.804 Signal, block.