Northern Line - Ride Quality (3)

MQT on 2015-03-25
Session date: 
March 25, 2015
Question By: 
Andrew Dismore
Labour Group
Asked Of: 
The Mayor


Is the Northern Line computerised drive system able to anticipate the needs of the next section of track, or is acceleration and deceleration purely calculated on the current instant of time and its 'actual against desired' speeds? Is this the missing factor, that train drivers unconsciously provided, and that your new system cannot?

Do you accept the ride is unacceptably jerky?


Answer for Northern Line - Ride Quality (3)

Answer for Northern Line - Ride Quality (3)

Answered By: 
The Mayor

The new Transmission Based Train Control (TBTC) signalling system scans ahead of the train and issues a target point to which the train drives, calculating the required speed as it goes.  Drivers would have done a similar action when driving to the old colour light signalling system where they were effectively given a permitted destination to drive to, and then would have driven up to line speed to that point. Trains are now able to utilise their full performance potential and are able to accelerate at nearly twice the rate (1.3m/s/s). Line speed limits in many areas have been uplifted and the TBTC system can cope with more frequent changes in speed limit to maximum performance.

The trains are operating within the Jerk Limits specified within London Underground's standards. TfL will continue to monitor performance on the line and make adjustments as required.