Editing LMS Coronation Class (section)

==== Automatic warning system ====
During the twentieth century, [[Signal passed at danger|signals passed at danger]] (SPADs) were increasingly perceived as a significant danger to the public. Only the [[Great Western Railway]] truly accepted the challenge posed. Prior even to 1910, it commenced installing [[Automatic Train Control]] (ATC), a system where each distant signal was accompanied by a ramp between the tracks with which a shoe on the locomotive would make contact as it passed over it. When the signal denoted "clear", an electric current would pass through the ramp which was detected by the shoe, thereby sounding a bell in the cab. With the signal at danger, the electric current would be cut off and when the shoe detected this it would activate a warning horn. In later forms, the brakes would be applied should the driver fail to acknowledge the warning.<ref>{{cite book |last=Rolt |first=L.T.C |author-link=L.T.C. Rolt |title=Red for Danger |edition=1st |year=1955 |publisher=The Bodley Head |location=London |pages=202–203}}</ref>

In 1952, the UK's most disastrous SPAD ever occurred at [[Harrow and Wealdstone rail crash|Harrow and Wealdstone]], in which No. 46242 ''City of Glasgow'' was severely damaged. The lack of an ATC system on most of Britain's railways was at last seen as an urgent issue. From 1956 the BR-designed [[Automatic Warning System]] (AWS) was installed. It was similar to ATC but relied on an induced magnetic field rather than an electric current and featured a visual indicator in the cab. The receiving system was installed on the Coronation class locomotives from 1959 onwards. The outward evidence of on-board AWS comprised a protective shield behind the front screw coupling, a box to house the necessary batteries immediately in front of the cab on the right-hand side and a cylindrical vacuum reservoir above the right-hand running plate.{{r|Baker|p=69}}