Gardiner was Metro chairman from 1953 until the end of 1961. During his tenure, Metro built numerous infrastructure projects, including the opening of the first subway line, start of construction of the second subway line, water and sewage treatment facilities, rental housing for the aged and the Gardiner Expressway, named after Gardiner. Metro also amalgamated the various police forces into one in 1956. It was a period of rapid development of the suburban municipalities of Metro. The population of Metropolitan Toronto increased from one million to 1.6million by the time he left office.