RIS-7706-INS Iss 1

This document sets out requirements and guidance to support the process of adding, removing or modifying a Lettered Differential Permissible Speed (LDPS) on the Great Britain (GB) mainline railway network.

This document sets out processes for determining whether an Lettered Differential Permissible Speed (LDPS) is appropriate and which LDPS may provide the best cost benefit. Implementation of the selected option will follow the usual industry processes of Network Change, Vehicle Change and Route Compatibility assessment, as appropriate. These processes are unchanged by this document. Rather than being a complete set of all requirements for use of an LDPS, the content of this RIS is complementary to requirements and guidance set out in other RISs, Railway Group Standards (RGSs) and National Technical Specification Notices (NTSNs).

Optional reading and resources:

Standards quarterly webinar - September 2022