Complex sentence: The local stopping service is operated by Northern Rail and is supplemented by frequent InterCity services between Leeds, Wakefield and either Doncaster or Sheffield operated by operators East Coast, East Midlands Trains and CrossCountry.
Split into simpler sentences: The local stopping service is operated by Northern Rail; it is supplemented by frequent InterCity services between Leeds, Wakefield and either Doncaster or Sheffield. Long distance services using this line as part of longer journeys are run by East Coast, East Midlands Trains and CrossCountry.