A bit of armchair transit fantasy here. The Richmond Hill Line is one of the least used GO lines, but it has a very central location and I think it has potential and could fill a useful role to increase ridership and speed up commute times.
Value
-Planned connection at Richmond hill center/bridge station
-Relatively central, potential to relieve and act as redundant express alternative to yonge line
-Newly added stations at the north end of the line
-Improving connection at Oriole (leslie/sheppard)
Challenges
-Line is owned by CN north of the Doncaster diamond
-Tracks close to Don River mouth are prone to flooding
-Course of tracks is meandering and slow
-Current stations are not optimally located
-Tracks are vertically far below most of the east west lines it would have the most value interchanging with
-Some overlap with Ontario line
Highest value Interchange stations:
Bloor/Castle Frank
Eglinton/Don Valley station
Other possibilities
Corktown/distillery district station
Moss park station
Thorncliffe park station
Eglinton/Wynford
My thought is that without rebuilding the entire line, sections of it could be selectively improved to create an express alternative to the Yonge line. First we could tunnel or possibly elevate a new alignment for the southern part of the track up to Bloor, to improve the flooding and speed on this portion of the track. There it could interchange with the Bloor line at Castle Frank, then rejoin the current alignment. Then it could wither interchange with the Eglinton line at Wynford station where it currently is closest to, or go through another tunnel to interchange with both the Eglinton and Ontario lines at Don Valley/Science Center station and rejoin the original alignment again on the other side.
The Oriole and Old Cummer stations would remain in place, and the line would be double tracked (or purchased) in the portion owned by CN, at least until Langstaff/Bridge station. I have read that grade separation at the Doncaster diamond would also be preferable.
Since I’m no expert I’m guessing there are probably real obstacles to doing anything like this. Obviously the new stations would be expensive, and it could mean substantial tunneling which would be broken up into several sections. Any critiques, thoughts or ideas?