Cookies on the Crossrail website

We use cookies to ensure we give you the best experience on our website. If you continue, we'll assume that you are happy to receive all cookies on the Crossrail website.

Find out why we use cookies and how to manage your settings.

Trial Running Explained

Trial Running marks a key point in the Elizabeth line’s transition to an operational railway overseen and maintained by Transport for London and is a critical step forward into passenger services. The railway is still on track to open in the first half of 2022.

It will see multiple trains operating in the central tunnels, and along the Great Western Main Line and Great Eastern Main Line to fully test the timetable, whilst the final works to the stations are completed.

The extensive commissioning of the railway commences with the Trial Running phase and involves integrated trials of the railway to demonstrate that the Elizabeth line is safe and reliable, and that it meets the capacity and performance requirements needed to move to the final commissioning stage.


During Trial Running, Crossrail will be building up the numbers of trains operating in the 42km of new rail tunnels that have been built beneath London. Multiple trains will operate in the tunnels and along the Great Western Main Line and Great Eastern Main Line to demonstrate how the infrastructure and operating software performs.

The initial phase of Trial Running will see a limited number of trains in operation in the central tunnels between Paddington and Abbey Wood to allow the infrastructure manager, Transport for London, to undertake a number of activities to achieve full readiness. The number of trains will gradually increase to enable further activities such as timetable operation, timetable demonstrations and integration testing to be undertaken.

Trial Running Slide 1

Outstanding works have been scheduled into the programme and will take place during the Trial Running period. These works include a combination of project maintenance, snagging and enhancements and some testing and commissioning activity.

There will also be four software upgrades that will take place during Trial Running when the programme will be suspended to facilitate the testing and commissioning of signalling and control systems software configurations.

Trial Running Slide 2


Trial Running Slide 3

Trial Running will demonstrate that the railway is capable of reliably meeting passenger capacity and performance requirements.

Trial Running is critical to increasing train mileage in the central section and supporting the reliability growth of the railway and demonstrate that the Elizabeth line can run at performance levels necessary to move into the next phase of the programme.

During Trial Running, we will run the system under timetable conditions to flush out any remaining software bugs or issues. This is so that we can fix them and demonstrate increasing reliability whilst running an increasing number of trains in the central operating section.

Once Trial Running has completed, a final phase known as Trial Operations will commence, which will involve over 150 scenarios in which volunteers will help validate the emergency evacuation processes in our trains, tunnels, shafts and stations.