[Code of Federal Regulations] [Title 49, Volume 4] [Revised as of October 1, 2003] From the U.S. Government Printing Office via GPO Access [CITE: 49CFR234.257] [Page 492] 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. 234.257 Warning system operation. (a) Each highway-rail crossing warning system shall be tested to determine that it functions as intended when it is placed in service. Thereafter, it shall be tested at least once each month and whenever modified or disarranged. (b) Warning bells or other stationary audible warning devices shall be tested when installed to determine that they function as intended. Thereafter, they shall be tested at least once each month and whenever modified or disarranged.