In-service testing has begun on ten 5000-series prototype rail cars by the US's Chicago Transit Authority (CTA).
The rail cars will be tried on all of the CTA’s eight rail lines through to the end of 2010.
The operator is expected to finalise the remaining 396 rail car orders after the successful running of the cars.
Bombardier Transportation was awarded a $603.6m contract to manufacture the 406 rail cars.
The cars are expected to replace the CTA's oldest rail cars such as the 2200-series Budd cars, bought in 1969-70, and the 2400-series Boeing-Vertol cars, purchased in 1976-78.
The cars are expected to offer seven networked security cameras, a new aisle-facing seating configuration, glow-in-the-dark safety signs and sensitive door sensors.
The seating configuration is also expected to have 38 seats and space for two wheelchair positions, and added support poles and hand straps for standing customers.