The British Rail 4-TC multiple units were unpowered fixed formation 4 carriage set (fitted with driving cabs at each end) converted by BR at York Works from locomotive-hauled Mark 1 carriages in 1966-1967 and 1974. The units built on experience gained from the prototype 6TC unit. They were initially classified as Class 442 and numbered in the 300 and 400 series. This was later changed to Class 491, under which they spent the majority of their working lives. Shortly before withdrawal they were reclassified Class 438 and the units were renumbered to 8001-8034.