236.12—Spring switch signal protection; where required.
Signal protection shall be provided for facing and trailing movements through spring switch within interlocking limits and through spring switch installed in automatic block signal, train stop, train control or cab signal territory where train movements over the switch are made at a speed exceeding 20 miles per hour, except that signal protection shall be required only with the current of traffic on track signaled for movement in only one direction.
Code of Federal Regulations
[49 FR 3383, Jan. 26, 1984]