Dollis Valley Viaduct

MQT on 2017-06-22
Session date: 
June 22, 2017
Question By: 
Andrew Dismore
Labour Group
Asked Of: 
The Mayor


The Dollis Valley Viaduct was built originally to accommodate a double track. However, a present the single track for tube trains is laid down the centre of the viaduct. What is the width of the viaduct; what width would be needed to accommodate double track; would it be possible from an engineering viewpoint to double track the line to Mill Hill East , given the fast growing population in the area; if not why not; and what would  be the cost of doing so?


Answer for Dollis Valley Viaduct

Answer for Dollis Valley Viaduct

Answered By: 
The Mayor

Transport for London (TfL) continuously reviews the Northern line timetable to ensure that services benefit the greatest number of customers. Trains to and from Mill Hill East Tube station currently run approximately every 12 minutes during peak time. This meets the current demand at the station and the forecast demand in the future.

TfL has previously investigated doubling the track at Mill Hill East however the total costs were prohibitive. While technically feasible, it would cost approximately £45m to replace the bridge, carry out the necessary re-signalling works, and install a second platform at Mill Hill East station.