Simplify the following text for a Grade 12 native English-speaking person.
Original: The Class 377 Electrostars are electric multiple units built by Bombardier Transportation ( previously ADtranz ) at their Derby Works , from 2001-present .
Simplified: The Class 377 Electrostar is an electric multiple unit type built by Bombardier Transportation ( previously ADtranz ) at their Derby Works , from 2001 to present .