Centenary of London's first three-colour traffic lights

The first three-colour traffic lights were introduced in London on 3 August 1926 as a trial. This marked a shift from earlier, less reliable systems to the red, amber, and green sequence used in modern road management. The Ministry of Transport ordered eight units for the trial, which were supplied by the Westinghouse Brake and Saxby Signal Co, according to ianVisits.

Implementation at Piccadilly

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The trial was concentrated on Piccadilly, specifically at the junctions with Berkeley Street, Dover Street, Albemarle Street, Old Bond Street, Arlington Street, and St James Street. Rather than directing motorists directly, the initial system was designed to instruct policemen on duty. A policeman in a cabin would operate a railway-style lever frame to change the lights, which then signalled to the officers at the junctions what actions to take. This method was intended to streamline the work of traffic marshals, as reported by ianVisits.

The Ministry of Transport expected the electric lights to save approximately £1,400 a year in police costs. This figure was intended to offset the expense of hiring traffic police to stand in the roads throughout the day. The trial faced delays because officials initially feared there would not be enough traffic during the August Bank Holiday to assess the system's effectiveness.

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Operational challenges

But I expect that the most successful will be to allow at intervals, a clear run up to Piccadilly

An official, as reported by the Morning Post

The system encountered early difficulties. Because the lights were meant for the policemen rather than the drivers, motorists occasionally drove through red lights if the officer failed to notice the signal change. By April of the following year, officials admitted that the system would be improved by adopting the French method. This involved raising the lights higher to control traffic directly, rather than using them as instructions for police officers.