My local train service runs two types of trains: double-decker (with 2/2 seats) and single-decker (with 3/2 seats). The single-level trains cannot comfortably

My local train service runs two types of trains: double-decker (with 2/2 seats) and single-decker (with 3/2 seats). The single-level trains cannot comfortably hold three average-size adults, so they effectively have half the capacity.