Simplify the following text for a Grade 14 native English-speaking person.
Original: However , they also have significant differences , such as fully longitudinal seating similar to that used on London Underground rolling stock to give more standing room , which is necessary for the high passenger volume metro-style services expected to be run on London Overground .
Simplified: Primarily , the Class 378 will feature fully longitudinal seating similar to that used on London Underground rolling stock , which is necessary for the high passenger volume services expected to be run on London Overground .