In 1866, a year in which 1,102 people were killed and 1,334 injured on roads in
London, Knight proposed a signalling system to regulate horse-drawn traffic and reduce the number of road accidents. Knight's invention was operated by a policeman and used a
semaphore system based on
railway signalling during the day, and red and green gas-powered lamps at night. The world's first traffic light was installed on 9 December 1868 in London near
Westminster Bridge, at the intersection of Great George Street and Bridge Street,
London SW1. However, in 1869, a gas leak caused one of the lights to explode, badly injuring the policeman operating it, and the system fell out of favour and was removed as a result. Traffic lights did not appear again in the
United Kingdom until 1929, when the first electric signals were introduced in London. A memorial plaque to Knight's invention can be seen at 12 Bridge Street, Westminster, the corner building close to where the original traffic lights were erected. Minister for Roads and Road Safety
Baroness Hayman unveiled the plaque on 4 March 1998. == See also ==