[Code of Federal Regulations] [Title 49, Volume 4] [Revised as of October 1, 2002] From the U.S. Government Printing Office via GPO Access [CITE: 49CFR234.203] [Page 475] TITLE 49--TRANSPORTATION CHAPTER II--FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION PART 234--GRADE CROSSING SIGNAL SYSTEM SAFETY--Table of Contents Subpart D--Maintenance, Inspection, and Testing Sec. 234.203 Control circuits. All control circuits that affect the safe operation of a highway- rail grade crossing warning system shall operate on the fail-safe principle.