Complex sentence: The initial order signed in 2006 called for the delivery of 234 cars, making for 39-six-car fixed trains, this allowed the TTC to retire the older H4 and H5 series trains and replaced them with the new TR series trains.
Split into simpler sentences: The initial order signed in 2006 called for the delivery of 234 cars, making for 39-six-car fixed trains. This allowed the TTC to retire the older H4 and H5 series trains and replace them with the new TR series trains.