49 C.F.R. § 236.708 Block.
Title 49 - Transportation
A length of track of defined limits, the use of which by trains is governed by block signals, cab signals, or both.
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
§ 236.708 Block.