High Quality Content by WIKIPEDIA articles! The Automatic Warning System (AWS) is a form of limited cab signalling and train protection system introduced in 1956 in the United Kingdom to help train drivers observe and obey signals. It was based on a 1930 system developed by Alfred Ernest Hudd and marketed as the "Strowger-Hudd" system. An earlier contact system, installed on the Great Western Railway since 1906 and known as Automatic Train Control (ATC), was gradually supplanted by AWS within the Western Region of British Railways.