Adhesion Prediction Tool Replacement

This notice is issued by TfL to notify the market of our intention to carry out market engagement and a potential future tender which may commence in March 2026.

The total contract value is unknown at this time we are embark on this market engagement process. This process does not commit TfL or potential suppliers to any spend.

The specification has yet to be developed, however the findings from this market engagement process will inform the final specification.

Scope:

To transport the high number of passengers required in a modern city constrained by legacy tunnels and platform lengths needs more frequent trains which in turn requires higher acceleration and brake rates. However, to prevent wheel spin under acceleration or wheel slide under braking requires a minimum level of adhesion (friction) at the wheel rail interface.

Adhesion Controllers Condition Assessment Tool (ACCAT) has been employed over the last 20+ years on the Central line and approaching 6 years on the Sub Surface Railway.

Using the underlying logic, the ACCAT processes weather data provided by a 3rd party and several other inputs to predict the available rail adhesion and outputs recommendations in the following three categories:

1. The operation of railhead treatment trains, thus improving the level of adhesion available to trains.
2. Brake rate reduction, thus reducing the adhesion required to stop the train. It also recommends when an imposed brake rate reduction can be removed
3. Severe weather warnings

TfL is interested in the innovation software development solutions offered by the market for the development of a custom adhesion prediction tool.