See I knew I would learn a couple of new things if I just let the discussion happen and come back to this thread like a few days later after some announcements were made in the press

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Just because I am posting this on the heels of other people comparing our proposed project to Montreal's REM transit project I will start with that... Montreal's proposed REM project is definitely an exciting one! Especially considering that they will be using similar, if not, identical technology to our Skytrain system. BUT if you really analyze the proposed project, you can see that a significant portion of that network will be at ground-level
but grade-separated. Also, you will notice that the portions of it that are underground, are not going through major neighbourhoods (to my knowledge) like the Broadway corridor AND that the underground portions aren't proposed to go long distances. I illustrate these points to say that because the Montreal REM system is mostly at ground level and/or elevated that it will be cheaper and easier to construct than our major underground system that we want down Broadway. I would compare the beginning of their REM system to the beginning of our Skytrain system; we started off the Expo line similarly by using formerly used freight-train tunnels and making it elevated to cut costs. Now I do think that having the REM system operating by 2020 is unrealistic at this point for Montreal but that's another post

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It's definitely not fair to compare Vancouver's transit system to the mega-metropolises like London or New York. But what we can do is learn from them on
how they approached construction for underground lines under major neighbourhoods. Because I am sure that one of these larger cities has constructed a major underground line through a densely populated neighbourhood. In fact, I think that centuries ago, London did construct one of its many lines (underground) that went through a major neighbourhood. And what they did was construct a temporary elevated road for vehicles while work was done underground. Someone may correct me if I am wrong here but I am 100% confident that there were projects similar to the Broadway extension that were considered successful. Bottom-line: We are not doing something unique in this world with this proposal.
The Broadway corridor itself is a major east-west connecting road. No matter what, there is going to be disruption on that street whether the extension is elevated or underground. Ideally I would like to see this extension done right the first time, and done right to UBC. I imagine that the construction will be an incredible disruption to the Broadway neighbourhood and as opposed to disrupting life multiple times, I say that we should just bite the bullet and get it over with. Because God knows, there is more than enough demand for Skytrain service
all the way to UBC today; and who knows what that demand will be like in 5-10 years?
And this brings me onto my next point; life will still go on before, during, and after construction. Someone else pointed this out before but I would like to repeat that we won't know what demands Vancouver will face in the next 10 years or what the challenges will be. I can guarantee, however, the longer we wait the more expensive this project will become. And with that will come more demands for infrastructure of all types. But one transportation project that has always stayed imminent in our minds when we think of the future, is the Millennium line extension down to UBC. And now is the time to get the shovels in the ground!