The concept of a broken up Green Line has been bandied about before. The South Portion would connect onto 7th Ave (which would be terrible for the current network, but would get the Green Line downtown the cheapest way). This would require the same cars as the current system. Then the North portion would be built separately, which is where the low floor trains were essentially for, and what would have the different options for downtown and not have the problem of needing to integrate with the south portion.This quote is hidden because you are ignoring this member. Show Quote
The biggest problem with such an option is adding even more congestion onto 7th Ave. Frequencies would need to be reduced on both Red and Blue Lines and in order to maintain capacity with the lower frequencies a lot of cars would need to be purchased to get everything to 4 car trains (in addition to the purchase of the cars for the south line as well; so hundreds of millions of dollars and a reduction in service for the two current lines). The way around this would be to put the Red Line underground which would result in the biggest service improvement across all of transit, reducing travel times and providing the largest capacity increase. Then it would just be the lower capacity Blue and Green south lines on 7th. Would be a very good option, improving the highest ridership line and leaving lots of room for future growth, but it isn't going to save any money, because you're just replacing a low-ridership tunnel option with a high ridership tunnel option (which is a good trade, really). Without that alternate tunnel option, such a plan is a pretty terrible one.
Where the terminus of the north line would go would be the biggest question mark for potential ridership for that leg. Not getting to the Stampede Grounds and event centre would limit it, but the transit option would still exist with a transfer, which isn't as big a deal as needing to walk. But not needing to directly integrate with a tunnel or at-grade option makes an elevated option more feasible. If the requirement of not needing to interfere with current vehicle traffic is removed, it can even be done somewhat cheaply.