Services were operated with 6 cars off-peak and 8 cars during peak hours until 1971, when trains were reformed as fixed 7-car trains, and some 6-car trains for the Edgware Road branch. The CO/CP and R Stock were replaced in the late 1970s by new trains with unpainted aluminium bodies. A shorter train was needed on the Edgware Road branch due to the platform lengths so more of the C stock units, then already in use on the Circle and Hammersmith and City lines, were built. The rest of the District line could use longer trains and new D Stock trains were introduced between 1979 and 1983. One person operation of the trains was proposed in 1972, but due to conflict with the trade unions was not introduced on the District line until 1985. In 2003, the infrastructure of the District line was partly privatised in a public–private partnership, managed by the Metronet consortium. Metronet went into administration in 2007 and the local government body Transport for London took over responsibilities.