Simplify the following text for a Grade 10 native English-speaking person.
Original: The Electrostar family , which also includes Classes 357 , 375 , 376 , and 378 , is the most numerous type of EMU built in the post-privatisation period of Britain 's railways .
Simplified: The Electrostar family , which also includes Classes 357 , 375 and 376 , is the most numerous type of EMU built in the post-privatisation period of Britain 's railways .