Section 235.5 - Changes requiring filing of application(a) Except as provided in § 235.7 , applications shall be filed to cover the following:(1) The discontinuance of a block signal system, interlocking, traffic control system, automatic train stop, train control, or cab signal system or other similar appliance or device;(2) The decrease of the limits of a block signal system, interlocking, traffic control system, automatic train stop, train control, or cab signal system; or(3) The modification of a block signal system, interlocking, traffic control system, automatic train stop, train control, or cab signal system.Approved by the Office of Management and Budget under control number 2130-0042