The Bombardier CR4000 is a 76% low floor model of the Bombardier Flexity Swift series of tram operated by Tramlink in London. They are based on and very similar in appearance to the K4000 used on the low-platform routes of the Cologne Stadtbahn network. Built between 1998 and 2000, the trams entered service in the spring of 2000.

The Bombardier Flexity Swift is a series of urban and inter-urban tram, light rail and light metro vehicles manufactured by Bombardier Transportation. It is part of the Bombardier Flexity family of rail vehicles, and like the others, Flexity Swift vehicles can be customized to suit the needs and requirements of customers including legacy designs from its acquisition of Adtranz.