Complex sentence: One hundred and ten Class 450 four-car units for commuter services entered service in 2003, and forty-five Class 444 five-car units for long-distance inter-city services entered service in 2004.
Split into simpler sentences: One hundred and ten Class 450 four-car units for commuter services which entered service in 2003. Forty five Class 444 five-car units for long-distance inter-city services entered service in 2004.