The trials were carried out on the fast tracks between Reading and Didcot and were managed by infrastructure manager Network Rail. Two test runs were made at speeds up to 200km/h. Electrification of this section has been completed first to enable it to be used to test the 25kV 50Hz power supply system, catenary and the trains.
An inaugural trip with a bi-mode set was made from Reading to London Paddington on June 30.
Network Rail is currently electrifying the entire line between Heathrow Airport junction and Bristol, Cardiff, Oxford and Newbury, and it says the first services with IEP under electric traction are scheduled to begin in 2019. However, Great Western Railway plans to start introducing the trains in diesel mode next year on services from London to Oxford, Bristol and Swansea, and the fleet will also replace HSTs on services to Cheltenham, Worcester and Hereford.