Board Slang for aVisual indication passed to a train driver to advise the speed, direction or route of the train. There are almost as many types of signals as there are railways but they fall into the following main categories:1) handsignals - used mainly where there are no fixed signals or where the fixed signalling has failed. 2) semaphore signals - a fixed lineside signal where the stop indication is displayed as a horizontally positioned arm and proceed as a 45º or vertical arm. 3) colour light signal - a fixed lineside signal showing light indications to drivers. 4) cab signals - where the indications are displayed in the driver's cab." class="glossaryLink ">signal 0 Related Articles: Glossary: Marker Board Glossary: PLB Glossary: whistleboard Glossary: RSSB Designing for Low Whole-Life Carbon - Decarbonisation Programme Workstream 13