Professor Sir Colin Douglas Buchanan (22 August 1907 – 6 December 2001) was a Scottish town planner. He became Britain's most famous planner following the publication of Traffic in Towns in 1963, which presented a comprehensive view of the issues surrounding the growth of personal car ownership and urban traffic in the UK.
Buchanan was born in 1907 in Simla, India, a descendant of a long line of Scottish civil engineers. He was educated at Berkhamsted School in Hertfordshire, before studying engineering at Imperial College, London. His first work was on bridges and roads for the Public Works Department in Sudan. Returning to the UK he then worked on regional planning studies, joined the Town Planning Institute, and in 1935 joined the Ministry of Transport where he worked on trunk road schemes and road safety.
After serving in the Royal Engineers during World War II and attaining the rank of Lieutenant-Colonel, he left to join the new Ministry of Town and Country Planning, overseeing planning enquiries into slum clearance and reconciling traffic, planning, and environmental policies.
In 1960 the Minister of Transport, Ernest Marples, appointed Buchanan to head a working group in the Ministry of Transport. In 1963 the group produced the influential Buchanan Report, which proposed how British towns could be redesigned to accommodate growing motor car use. Car numbers in the UK were expected to quadruple over the coming decades. In 1964 Penguin Books published Traffic in Towns, which was a concise version of the 1963 Buchanan Report. Buchanan's policy recommendations were widely accepted and became a blueprint for urban redevelopment until the end of the century.