If there are curves in a tunnel where more than one train or locomotive operates, block signals for each curve shall be installed and used. These signals may be manually operated from each approach to the curve or turn if arranged so as to give effective notice that a train is on the curve.
Cal. Code Regs. Tit. 8, § 8477
Note: Authority cited: Sections 142.3 and 7997, Labor Code. Reference: Sections 142.3 and 7997, Labor Code.