Simplify the following text for a Grade 11 native English-speaking person.
Original: Thirty of these units , designated Class 350\/1s , were built for use by Central Trains and Silverlink on regional express services and services on the southern section of the West Coast Main Line .
Simplified: Thirty of these units , known as Class 350\/1s , were built for use by Central Trains and Silverlink on regional express services and Central Citylink services on the southern section of the West Coast Main Line .