The trains are part of a 3.4 billion pound contract that was awarded to Bombardier by Metronet. The contract was to supply new trains featuring Automatic Train Operation and signalling for the Victoria and sub-surface lines. When it is finished this upgrade should make the lines and trains more reliable. There should also be an 8% decrease in journey times between stations, and a 16% overall decrease in journey times. This decrease is partly because the new trains have better performance than the 1967 tube stock that they are replacing. The new trains have a higher top speed of , a faster maximum acceleration of 1.3 m/s, a normal service deceleration of 1.14 m/s, and an emergency brake deceleration of 1.4 m/s. This is the same as the 1992 tube stock.