The reliability of this fleet has been outstanding, being consistently between 30,000 and 70,000 miles per casualty. Since they work on a commuter service with numerous stops it represents a major achievement to be the UK’s most reliable EMU. Built by Adtranz (now Bombardier) in Derby, the units are constructed of huck-bolted aluminium extrusions with steel cabs, similar to Turbostars, but 20 metres long rather than 23. Electrical Equipment is from Vastereas in Sweden, a factory renowned for many years for advanced traction equipment supply. Air conditioning, PIS system, air suspension and MITRAC train management system are all fitted, making this a highly advanced train. Availability is also excellent, with 96% being the target , consistently achieved. The interior uses Chapman seats in 2 x 3 configuration, with some bay seating an tables at the outer ends. The safety case allows running with all types of track circuit in the UK, although some tests would be required to clear new areas.