[Code of Federal Regulations] [Title 49, Volume 4] [Revised as of October 1, 2005] From the U.S. Government Printing Office via GPO Access [CITE: 49CFR234.213] [Page 573-574] 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. 234.213 Grounds. Each circuit that affects the proper functioning of a highway-rail grade crossing warning system shall be kept free of any ground or combination of grounds that will permit a current flow of 75 percent or more of the release value of any relay or electromagnetic device in the circuit. This requirement does not apply to: circuits that include track rail; alternating current power distribution circuits that are grounded [[Page 574]] in the interest of safety; and common return wires of grounded common return single break circuits.