Human Factors Assessment of Automatic vs Manual Train Operation
London Underground
Background
As part of the modernisation of the Underground network, new signalling and train systems were being installed on the Piccadilly Line. However this upgrade did not extend beyond South Harrow towards Uxbridge and it was planned to continue to use manual train operation, with lineside signalling and Trainstop protection, in this section of the route. The operation would require Train Operators to manually switch from Automatic Train Operation to manual operation from the starter signal at South Harrow (Westbound) and therefore manually operate trains that have been previously operated in ATO mode for some time in the preceding sections of route with a potential increase in human/driver error.
Project
To prove that this proposal was safe a quantified human factors risk based comparison of current fully manual operations versus the proposed future dual ATO operation and manual operation was delivered by CCD.
Implementation
The work assessed and compared human error rates in relation to the operation of both ATO and manual operation for train operations in the future, versus current error rates in relation to driving only in manual mode. The scope of work covered the impact of dual mode operation (and the associated impact of changes of mode) on human error rates in relation to safety critical tasks (such as the observation of lineside signals, platform tasks and SPADS). Over 100 potential human errors were identified with eight tasks having significant safety consequences. Human error quantification was delivered using the HEART methodology which assessed there to be 9 events with a realistic and probable chance of error which would require mitigation before the proposed system was safe under the ALARP principle.
Outcomes
On this project, CCD was able to assess the proposed solution in a formal manner, involving all stakeholders, to deliver a quantified and robust analysis. This gave the client a clear and prioritised direction on where their actions and focus should be to improve the system development to a level that would be accepted by the safety authorities.