Editing Automatic Warning System (section)

{{Short description|Railway safety system in United Kingdom}}
{{Use dmy dates|date=April 2015}}

[[File:D5401 AWS 260108 d.adkins.jpg|150px|thumb|The AWS 'sunflower' indicator inside a [[British Rail Class 27|Class 27]] showing a warning indication has been acknowledged.]]

'''Automatic Warning System''' ('''AWS''') is a railway safety system invented and predominantly used in the United Kingdom. It provides a train driver with an audible indication of whether the next [[Railway_signal|signal]] they are approaching is clear or at caution.<ref name="Awsrules">{{cite web| title =AWS & TPWS Handbook: Section 1.1.3 "The purpose of AWS"| url =https://www.rssb.co.uk/rgs/rulebooks/RS522%20Iss%203.pdf| publisher =RSSB| access-date =2017-02-07| archive-date =5 December 2016| archive-url =https://web.archive.org/web/20161205171951/http://rssb.co.uk/rgs/rulebooks/RS522| url-status =dead}}</ref>
Depending on the upcoming signal state, the AWS will either produce a 'horn' sound (as a warning indication), or a 'bell' sound (as a clear indication). If the train driver fails to acknowledge a warning indication, an emergency brake application is initiated by the AWS; if the driver correctly acknowledges the warning indication, by pressing an acknowledgement button, then a visual 'sunflower' is displayed to the driver, as a reminder of the warning.