For the construction phase, monitoring of performance was undertaken through milestone achievement. As part of the payment mechanism, this approach served as an effective indicator of performance during the construction phase. These milestones were monitored by the Procuring Authority and Project Company, as well as an independent certifier.

There were approximately 1,000 milestones on the project, covering over 25,000 individual activities, which made ongoing performance monitoring a challenge. There were 12 key milestones, which were spaced 4-5 months apart and were used as an indicator of integrated progress. They were also useful for judging how the civil works were progressing compared to the rolling stock and systems delivery. On completion, both parties would inspect the delivered works with an independent certifier who is the only party authorised to certify compliance and progress of the work and issue a payment certificate to the construction contractor for the completed works.

In the operations phase, there are 25 measurable criteria against which performance of the Project Company is monitored each month, with potential deductions to be applied in case of failure to meet the standards. The performance criteria are monitored by the Project Company and reported to the Procuring Authority on a monthly basis. The monitoring and recording system is as automated as possible and manual interventions are minimised, and the payment mechanism prescribes deductions to unavailability of service or poor performance.

One KPI is a social development criterion, which sets a range of monthly targets related to training and employment of male and female historically disadvantaged individuals and has related non-compliance payment deductions. This reflects the government's objective to create jobs and improve social mobility of disadvantaged populations.