The railway companies have, and still do, issue notices of changes to signalling arrangements. They are produced primarily to inform drivers, guards and signalling staff of those changes and generally only record changes visible to those groups of staff. Because of that, less visible changes or those not visible outside the confines of the signal box or signalling centre rarely, if ever, appear.

Over the years practices have varied between issuing bespoke notices, incorporating the information in a wider ranging publication, or a combination of both.