Complex sentence: The Queen Subway plan was cancelled in 1974 in favour of new lines in North York, however plans from Toronto and Ontario now necessitate its construction within the next 20 years to relieve pressure from the growing ridership on the Yonge subway line.
Split into simpler sentences: The Queen Subway plan was cancelled in 1974 in favour of new lines in North York. However,, plans from Toronto and Ontario now necessitate its construction within the next 20 years to relieve pressure from the growing ridership on the Yonge subway line.