Transport for London has tested a new computer-based signalling and control system on the London Underground, which is expected to ensure faster and reliable services. The new signalling system has been developed by Thales and is due to enable the trains to run closer and offer a more frequent service to the Circle, District, Hammersmith & City and Metropolitan lines. It is also expected to reduce signalling problems along certain sections of the Circle and Hammersmith & City lines and assist in providing accurate real-time information for customers on these networks. All four lines are expected to begin using the system by 2023.