The organization of Indian railways into regional zones began in 1951, when the Southern (14 April 1951), Central (5 November 1951), and Western (5 November 1951) zones were created. Fans and lights were mandated for all compartments in all passenger classes in 1951, and sleeping accommodations were introduced in coaches. In 1956, the first fully air-conditioned train was introduced between Howrah and Delhi (Presently known as Poorva Express). Ten years later, the first containerised freight service began between Mumbai and Ahmedabad. In 1974, Indian Railways endured a 20 day strike, which damaged the nation's economy.