Simplify the following text for a Grade 6 native English-speaking person.
Original: Fifty-three 9-car units were originally built for Virgin Trains from 2001 to 2004 for operation on the West Coast Main Line ( WCML ) , with a further four trains and 62 cars built during 2010-11 .
Simplified: Fifty-three 9-car units were built for Virgin Trains from 2001 to 2004 .