Let's stipulate:
1) "Greater Alewife" is everything in Cambridge from Mass Ave to Fresh Pond and from Sherman St (Danehy Park) to Brighton St (Belmont Line)
I'll field this one since I stared out at Danehy from my back window for 9 years.
No...up to Sherman is pretty clearly North Cambridge with more of a Mass Ave. affinity. This has to do with Danehy being the former town dump creating a firm and smelly wall between the neighborhood and Alewife until it was capped in the mid-80's. And also has to do with the apartment blocks on upper Rindge Ave. being low-income and prejudices therein. Field St. behind the former Armory and Rindge west of the cemetery at start of the apartment blocks are where the neighborhood identity starts to flip. And it's a very weak flip, mind you, since there historically has been so little residential near Alewife.
Belmont has absolute-zero affinity with that area. Wetlands have them 100% separated to this day from Acorn Park and Cambridge Park. You can even see the city line without ever seeing a line on a map in the way the street grid north of Concord Ave. breaks hard at the border with 100% residential on the Belmont side and 100% commercial/industrial (formerly all-industrial) on the West Cambridge side. The bike path is not an identity-changer in itself; the distinctions at the border and isolation-by-wetlands of each side are still sharp.
2) Assume Green has come out from Union via Porter and will continue on to "Greater Alewife" and that Porter is "by then" a "Super Station" where GLX2, RL, & Fitchburg RER meet
...and buses. Don't forget about the 77/77A and 96 are monster-ridership routes.
"Greater Alewife" will
not be part of the Union-Porter base build because it would (1) require an expensive treatment of the Sherman St. grade crossing that really would be far too much work for a +1 to the Parkway, and (2) it jumps the gun on exactly which extension--Watertown or Waltham--would come first.
The Sherman crossing is a legit nightmare; the best (from other threads) I could come up with was trolley duck-under but CR staying at grade because changing the level for both modes at once may be impossible (yes, I've stood on it and stared for collective hours over the years I lived down the street trying to figure this one out). As for extension demand, it's far more likely that
Watertown is going to crest before Belmont/Waltham given the building boom around Arsenal. So even if someday both branches ultimately become likely, the project pecking order any sets of data are going to point to is H2O #1, Waltham #2. Therefore, stub-out at the Parkway is not a good idea. You'll get a stop behind the Mall anyway if Watertown gets built, so "Greater Alewife" won't be starving for new transit touches. It's only about which touch gets scheduled first.
Keep in mind as well: that 1000 ft. separation from the Red station + buses referenced a page ago re: CR station demand is still in effect with Green. While the 6-min. frequencies of a Green branch would merit the stop in a way that 15-min. Fitchburg Urban Rail frequencies almost certainly would not...it's still not going to be a world-beater on ridership because of the gaping disconnect from the multimodal station and the off-center placement from the Cambridgepark office buildings. It's a necessary stop on the route to Waltham, but it is most definitely not a big 'get' on ridership at all and shouldn't be overvalued.
3) That Greater Alewife should have a station for each of the 3 services taht were/will be at Porter, but, given Porter as a hub, a transfer station isn't strictly needed.
No. CR frequencies, even at Urban Rail, aren't going to be good enough to beat: exit CR @ Porter --> escalator --> 2 stops on Red --> exit Red @ Alewife. Not when majority of the commuting jobs are fewer footsteps from the Red entrance than they are to the CR entrance with its steep hillsides and/or switchback ramps. You can time the savings in footsteps via Porter and come out ahead at those frequencies. Now, if some businessperson wants to give a charitable donation to building that CR platform few would waste the footsteps getting to, that's their problem. But as before, I doubt after taking a survey of their own employees on which station is an easier commute that they'll find a CR stop to be money ever worth spending.
Green, being rapid transit, needs to keep somewhat representative station spacing so an extension to Waltham is obviously going to stop at the Parkway...poor integration and all. 6-or-better min. headways are enough to stay competitive with the footstep math, but as noted...it will not be a barnburner on ridership, just an "OK enough" nip at the fringe. It'll still be down a steep, steep hill via a lot of footsteps on ADA-graded ramps to get from the parkway to trackside, and there's no sugarcoating that it'll be kind of a pain in the ass.
4) That, if you demolish the Alewife garage and rebuild it "better" you are also freer to line up services with their 40-year-plan outer terminus.
I have no idea what this means. But if you're hot to demolish a garage that's not at end-of-life, there better be some very compelling data points snapping to that "40-year-plan" (whatever that is). I don't think "Let's talk about nuking that bastard!" precedes talk of the demographic trending in any way/shape/form. And what is a "better" garage, anyway, when it's the wetlands that are shaping the constipated road access here and a 1970 highway cancellation that dumps an expressway onto city streets beckoning some sort of Pn'R presence to play goalie on those cars? Is Route 2 somehow not going to be terminating at Alewife in another 40 years?
5) Let's also note that if we do RER/Regional Rail right, the Fitchburg should end up having frequent service to Waltham.
So you've got 3 lines to play with, and roughly 5 corridors to put them on:
- Rt3/Lowell St to Burlington (via a turn northward at Arlington Center)
- Mass Ave / Minuteman Bikeway to Hanscom
- Rt2 to Rt128
- Fitchburg Line to Waltham
- Bike path to Mt Auburn & Watertown
And by "Corridor" I mean "generally following the established alignment" but "don't hold me to exactly within the state-owned ROW"
Seems to me the Crazy Pitch should be
1) Fitchburg should be electrified and get service every 10 minutes via Beaver Brook, Waltham, Brandeis to a new Park and Ride terminus on the Waltham-Weston line.
15 mins. They can't turn MU's around quite that fast with all the mandatory FRA tests for changing ends.
Also, you DO need to weight the state-owned corridors more heavily because private property is such a real nightmare to engage. Your realistic corridors are:
- Fitchburg Line, Union Sq. to West Cambridge (ex- Tracks 3 & 4 berth northerly side + short Porter subway, portal on southerly side)
- Watertown Branch landbank, West Cambridge to School St., Watertown + TBD (street-running?) to Watertown Sq.
- Lexington Branch landbank, Thorndike Field to Arlington Center (tunnel to Arlington HS)
- Lexington Branch landbank, Arlington Center-Hanscom AFB
- Eversource power line ROW, Hanscom AFB-Burlington Mall
- Fitchburg Line, West Cambridge to Route 128 (ex- Tracks 3 & 4 + widening of 1955 Waverley grade separation, southerly side, to Clematis Brook; complete displacement of Fitchburg CR Clematis Brook-Route 128
- Central Mass landbank, Clematis Brook to Route 128 (relocation of Fitchburg CR around Waltham Ctr. displacement)
It's not even reliable for a Crazy Transit Pitches thinkpiece to posit that the same towns that threw up a successful highway revolt against Route 3 are going to allow property-takings or years of destructive digging on the exact same corridor. Absolutely, positively forget about Lowell St. being a "corridor". I've never even heard a fantasy Burlington reach that attempted to break off any sooner than Lexington Center.
2) That Red should go out whichever "not Fitchburg" is densest
The tunnel already goes 1/3 mile out of the 1-1/2 miles to Arlington Center, so that's pretty self-explanatory. Arlington, while lower in total population than Waltham, has unbroken density out to Arlington Heights while the Fitchburg corridor is chopped up by large tracts of wetlands between density concentrations. Multimodally that gives Arlington more uniformly-heavy patronized buses to plug in and amplify the ridership effects. Then amplify further when some of the Alewife routes to Belmont, etc. get reorganized out of AH terminal to trim the route duplication. Waltham, while a big bus terminal, has a pronounced directional skew south into Newton and northwest crawling 128 because east-west the grid is heavily shaped by the wetland tracts.
If you're looking for what'll produce the most new transit riders immediately, it's Arlington where the rapid transit extension immediately creates a much more inviting bus network that can then be revamped/enhanced to superlatives. Waltham is simply going to require more preliminary multimodal development--and time--to achieve similar effect because its feeders' geographical skew is what it is.
3) Green go out whichever is next dense after the Red gets its pick
Which would be Waltham, per above on which is a faster reach for stimulating ridership from feeder sources.
But, hate to be beating a dead horse here: Red
already points to Arlington, Green
already points to Watertown and Waltham. Which line to where is not a debate that would ever be held in the real world, because risk assessments are part of project scoring. Blowing up a garage or section of tunneling intruding on the property + utilities + possibly building of a private abutter, or taking on an ironclad requirement to eliminate all grade crossings when some project to be brutal are all huge risk factor demerits. Going off a state-owned ROW in a desperate reach for...
something personally preferred?...is a significant risk factor and red flag.