system (AWS). This was an intermittent train protection system that relied on an electrically energised (or unenergised) rail between, and higher than, the running rails. This rail sloped at each end and was known as an ATC ramp and would make contact with a shoe on the underside of the passing locomotive. The ramps were provided at distant signals. A development of the design, intended for use at stop signals, was never implemented. If the signal associated with the ramp was at caution, the ramp would not be energised. The ramp would lift the shoe on the passing locomotive and start a timer sequence at the same time sounding a horn on the footplate. If the driver failed to acknowledge this warning within a preset time, the brakes of the train would be applied. In testing, the GWR demonstrated the effectiveness of this system by sending an express train at full speed past a distant signal at caution. The train was brought safely to a stand before reaching the home signal. If the signal associated with the ramp was clear, the ramp was energised. The energized ramp would lift the shoe on the passing locomotive and cause a bell to sound on the footplate. If the system were to fail then the shoe would remain unenergised, the caution state; it therefore failed safe, a fundamental requirement of all safety equipment. The system had been implemented on all GWR main lines, including Paddington to Reading, by 1908. The system remained in use until the 1970s, when it was superseded by the British Rail Automatic Warning System (AWS). North America Canada Starting in 2017, the Toronto Transit Commission began the implementation of ATC on to Line 1 Yonge–University, at a cost of $562.3million. Awarding the contract to Alstom in 2009, the TTC will be able to reduce the headway between trains on Line 1 during rush hours, and allow an increase in the number of trains operating on Line 1. Work would however not begin until the delivery of brand new trains with ATC compatibility and the retirement of older rolling stock that was not compatible with the new system. ATC was introduced in phases, beginning with a test on November 4, 2017 during regular service between Dupont and Yorkdale stations. It was first introduced in a permanent manner with the opening of the Toronto–York Spadina subway extension in December 17, 2017,