I have no data facts, but it seems obvious that the city badly needs a high quality, relatively speedy (ie faster than auto on increasingly congested roads) transit line well north of Eglinton, linking the far end of Scarborough to Etobicoke and beyond, and directly competing with the 401 in particular
The options boil down to
- extend the Sheppard line - because it is a sunk cost, and hence a cheap starting point, with considerable upside if extended in both directions so it is truly integrated to other lines
- plan a whole new line on some different route, duplicating Line 4 across the Yonge-DVP segment
- downgrade the existing Line 4 to some less expensive technology and extend at either end, likely either on or above ground
I'm guessing that the cost of duplicating the Yonge-DVP segment, using some technology other than subway, would match or exceed the savings if Sheppard is extended utilising the currently built line.
And I can't see other technologies, as good as they may be in some applications, meeting the need when the full bridge-across-top-of-city are considered.
One might argue for a line way up at the 407 - I would say yes, we need that also, and perhaps it ought to be closer to GO technology with fewer stops and much wider stop spacing, and higher top speeds - to really compete with highways 401 and 407.
So I can't object to just extending Line 4 as a vanilla TTC subway, and this seems to have less risk even if it's not the highest passenger counts of the subway system. (There was a time when the University line didn't run at nights or on weekends - funny how the ridership did turn up later). it's a pragmatic solution, and while others may be able to envision newer or more elegant modes, it's a devil we know well.
Both doable for less than the price of a 401 tunnel, I would add.
- Paul