Siemens has begun the construction of the first Class 707 Desiro City trains, built for South West Trains (SWT) in the UK.
The main body has been created and assembled.
The new fleet of trains are part of a £210m contract signed by SWT in last September with Siemens and Angel Trains.
The 30 new five-carriage trains will improve passenger facilities and increase space to accommodate 18,000 more passengers on some of the busiest services in the country.
South West Trains engineering director Christian Roth said: "The introduction of the brand new Class 707 Desiro City trains is an absolutely crucial part of our plans to provide the biggest increase in capacity on this network for decades.
"When delivered, these new trains will provide a major increase in spaces for passengers, as well as much improved facilities, including better accessibility and free Wi-Fi."
The trains are being assembled at Siemens’ Krefeld facility in Germany, with the first unit expected to be built by the end of February 2016.
Testing of the first train will start in May 2016 before being delivered by Angel Trains to SWT Wimbledon depot. The SWT staff will be trained on the systems, before the service begins.
Passenger service on these new trains, between London Waterloo and Windsor, is scheduled to start in June 2017.
According to Siemens, the new fleet is expected to be delivered by the end of 2017.
Siemens Rail Systems managing director Steve Scrimshaw said: "We are now turning the designs into reality and drawing closer to the next key milestone, the first complete train running around our test track before the ultimate goal, delivering new, spacious and comfortable trains that really improve the passenger experience."
The second-generation Desiro City trains are similar in style to the Class 700 units.
Image: The main body of the Class 707 Desiro City train created and assembled. Photo: courtesy of Siemens.