South of River St., the Bayview extension and the LRT could be stacked on top of GO, with GO in a flood-proof tunnel, like the RER along the Seine, with a walking/bike path along the river.
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The Bayview extension could be elevated to run flush with Gerrard, Dundas, and Queen, like the boulevard in Sarajevo beside the River - with a long LRT/GO/TTC station between Dundas & Queen. 
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Since the DRL is going to go under Eastern Avenue, the LRT could branch west at Dundas, Queen (or to enter a portal and merge with the DRL) and King, while GO continues to Union.
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Surface running on Dundas, Queen and King takes pressure off Union.  That means nested gauges.  Easier to get rid of TTC gauge.
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It could move 40,000 riders/hour.
It would take so much pressure off the Yonge line.
It could run all the way to Richmond Hill.
It would cost nothing compared to the DRL.
It could be in service at least a decade before the DRL.
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It could be so beautiful.
So incredibly, stunningly, beautiful.