Again...WHY is that preferable to the at-grade UR build that can do up to 3-minute LRT headways through the uneliminable grade crossings? Everyone has their preferences, but this is a project with hundreds of pages of Major Investment Study benchmarked for TWO different modes that could meet the service thresholds. It isn't begging for questions on how to HRT it, unless the HRT tie-in somehow pipes a ridership source orders of magnitude above and beyond what Green-hooked LRT or a BRT line would. The Study is extremely detailed on exactly where the ridership patterns into Kendall are coming from, so it's very unlikely they left a Blue source unturned under a rock that would slug something cosmically different from what the official study did. Therefore, when an alt is proposed that invites an order of magnitude more complexity (and yes, this is way more complex because an El is more expensive than at-grade, very different for stakeholder input, and still has one unsolved blocker in how to get across Main St. with the air rights overhead and Red tunnel passing underneath)...the justifications for it have to point to something hard and concrete on the demand side that's hugely better for inviting all that extra . And definitely better enough to triumph over the added risks.I've always liked the idea of sending the Blue Line across the river after MGH, then taking the Grand Junction, though I usually have imagined it as an above ground solution. Really, the ROW seems perfect for an elevated HRT line, which would then leave the possibility for also using it for the urban ring. Let the HRT continue out to West Station and Harvard, while the Green Line loops back inbound at the BU bridge.
If it can't answer that basic question, then we're not really debating Transit Pitches. That's the minimum-most standard we hold the Crazy Transit Pitches thread to, afterall...what's the mobility hook? It's one thing to try something on an unstudied corridor with a testable theory and hash it out as a thinking exercise...but this most definitely isn't an unstudied or under-studied corridor.