49 C.F.R. § 236.22 Semaphore signal arm; clearance to other objects.
Title 49 - Transportation
At least one-half inch clearance shall be provided between semaphore signal arm, and any object that may interfere with its operation.
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 A—Rules and Instructions: All Systems
Roadway Signals and Cab Signals
§ 236.22 Semaphore signal arm; clearance to other objects.