Eglinton LRT: speed and demand
Secondly, if they do achieve that 30-31 kph speed from Don Mills to Pearson - on one hand it is nice, but on the other, it can create a problem.
The ridership projections (5,400 pphpd per this display panels; 7,000 - 8,000 pphpd per other estimates) are, most likely, based on the assumption that Eglinton LRT will be somewhat slower than Bloor subway. If so, passengers for whom Elginton Crosstown is the shortest route will use it; but many other passengers, including those traveling from the north to downtown, will mostly stay in their buses until they reach Bloor subway. In that case, Bloor subway will continue to carry more people than Eglinton LRT.
However, demand in Eglinton corridor will obviously be very dependent on the speed. If the LRT in the west is as fast as subway, many people will switch to using it instead of Bloor subway. In fact, demand in Bloor and Eglinton corridors will likely be very similar. If so, we have to assume that about half of Bloor's peak demand (24,000 pphpd) will shift to Eglinton, and then we are at 12,000 pphpd already. Adding the ridership growth due to population growth and increase of the transit modal share, we can easily reach 15,000 or 18,000 pphpd.
If so, handling that demand with LRT technology might be difficult. Currently, TTC is planning 3-car (about 500 people) trains on 3-min headways (20 trains per hour), that means capacity of 10,000 pphpd. To get more than that, they would probably have to run short-turns in the tunneled section, for a combined 1.5 min headways there. And even then, there may be issues with the load balance between the short-turn and the long-haul branches ...
So, it almost sounds like, either build subway, or make LRT a little slower so it does not divert too many riders from Bloor : )