What is the nickname of Glasgow's underground transport system?

The Glasgow Subway is an underground metro line in Glasgow, Scotland. Opened on 14 December 1896, it is the third-oldest underground metro system in the world after the London Underground and the Budapest Metro. It is the only heavy rail underground metro system in the United Kingdom outside London, and also the only one in the United Kingdom which operates completely underground. It is also one of the very few railways in the world with a track running gauge of 4 ft (1,219 mm). Formerly a cable railway, the Subway was later electrified, but its twin circular lines were never expanded. The line was originally known as the Glasgow District Subway, but was later renamed Glasgow Subway Railway.

The origin of the Subway's supposed, but seldom used outside the press, nickname, "The Clockwork Orange" (coined from the title of the book and film A Clockwork Orange) is subject to dispute. Some believe that it was originally coined by the media of the period, whilst others credit it to the then chairman of British Rail, Sir Peter Parker, who was quoted in a late 1970s publicity video of the new trains as saying "so these are the original Clockwork Orange". Most of its carriages were painted orange the corporate colour of Greater Glasgow Passenger Transport Executive at the time. Most of the units have since been replaced with a new colour scheme of carmine and cream with a thin orange band, which will be implemented progressively throughout the fleet as cars are refurbished.