Signal W311 at Westbury in Wiltshire is a four-aspect filament-bulb signal installed in the 1980s. Although showing a red ('stop') aspect on the main signal head, the two white lights to the left give permission for a train to pass as a shunt move and the illuminated letters 'TS' indicate that the route is set into the Trowbridge Siding. if the main signal was showing a 'proceed' aspect then the larger indicator above the two white lights would should the route, for example by <a href="//commons.wikimedia.org/wiki/File:2015_at_Westbury_station_-_signal_W311_(also_W411_and_W511).JPG" title="File:2015 at Westbury station - signal W311 (also W411 and W511).JPG">showing a 'T' for the Trowbridge route</a>.
<a href="//commons.wikimedia.org/wiki/User:Geof_Sheppard" title="User:Geof Sheppard">Geof Sheppard</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>