the british rail class 303 is a type of electric multiple unit. they are also known as "blue train" units. they were introduced in 1960 for the electrification of the north clyde and the cathcart circle lines in strathclyde. at first they were classified as am3 units before the introduction of the tops classification system. they were the dominant emu on the glasgow suburban railway network for over 25 years. the final units were withdrawn from service in 2002.