 Trains are generally formed of a single unit (4 cars) or two units (8 cars) working in multiple during off-peak times, and strengthened to two or three units (12 cars) during the morning and evening peak times.71 of the 74 units are required to run the current normal timetable.Five units were loaned to sister National Express operator National Express East Anglia (then branded 'one' Railway) for a period ending in 2006 to accommodate the transfer of three Class 321/3 units to Silverlink (themselves to cover for Class 321/4 units hired to Central Trains).