Greater Anglia has begun training its drivers to operate the new trains that will be used on its route from Cambridge to London Liverpool Street.
The entire fleet on the route, which goes via Bishop's Stortford and Harlow, will be replaced over the course of this year.
Around 250 drivers need to be trained on the five-carriage units; most have already spent time in a simulator getting used to the controls, and the next stage of training will focus on how the trains handle in reality as well as emergency situations.
Andrew Goodrum, Greater Anglia’s business readiness director, said: "The start of training for our driving instructor colleagues who work on the west Anglia route is the next stage in our new trains introduction programme.
"Feedback from our instructors has been overwhelmingly positive - they see these new trains as a huge step-up and are proud to be playing a key role in getting them into passenger service."
The electric units have already been introduced on routes to Southend, Braintree and Southminster in Essex.
Eventually, the 133 sets will operate all of Greater Anglia's commuter services into London from Essex, Suffolk and Cambridgeshire.