BS EN 15153-4:2020 pdf free.Railway applications一External visible and audible warning devices.Audible warning devices for urban rail. BS EN 15153-4 1 Scope This document defines the functional and technical requirements for exterior audible warning devices for urban rail vehicles as defined in the CEN-CENELEC Guide 26, i.e. metro systems, trams, light rail, and local rail systems. This document also defines the...