Your correspondent Peter Smith (NCE 28 July) raises the issue of the length of trains assumed in the design for Crossrail.
We are planning services based on 10 car trains, each 20m long. This is compatible with the length of platforms available and under construction at Heathrow Airport. Heathrow Express has recently upgraded to nine cars each of 23m, not 10 cars as your correspondent suggests.
The platforms at the new underground stations in central London will have a total length of 240m with only 200m fitted out initially. This is to allow for future lengthening of trains to 12 cars. Clearly platform extensions would be impossible to construct once the railway is in operation.
When most Crossrail trains are extended to 12 cars it will be necessary to continue to run 10 car trains to Heathrow Airport.
The length of individual cars is not really an issue on a heavily trafficked railway such as Crossrail. The need to keep dwell time in stations to a minimum requires many doors, evenly spaced along the side of the train, and adequate provision for circulation inside.
The previous design for Crossrail was based on 23m length cars. The system would have initially been constructed for eight car trains with passive provision for future extension to 12 cars.
Keith Berryman, head of operations and development, Cross London Rail Links Limited, 1 Butler Place, London SW1H 0PT