Should be noted that the majority of optimization benefits that can work for OL, can be added to Line 1 in the future. Signaling can be upgraded, train layout can be improved when it's time to procure new trains, etc. OL can have those advantages at the start, but the Yonge line can get them as well, somewhat later but at a reasonable cost.
Another point worth noting is that a higher speed, by itself, does not lead to a higher capacity. Capacity is the product of trains-per-hour and riders-per-train. The latter depends on the train size and layout, and doesn't depend on the speed. Trains-per-hour is 3600 divided by the minimal allowed headway in seconds. With a higher speed, trains have to stay further apart to run safely, but the train covers that higher distance faster because of the speed. Thus the headway, expressed in seconds, remains the same.
The Yonge line might have some permanent operational disadvantages due to the legacy features, such as the tight station spacing in downtown, or the tight curve from the Yonge alignment to Union. Those could be making it difficult to maintain the optimal headway, and thus reduce the capacity somewhat. But by how much? Probably no more than 10%.
stevemunro.ca
