This image is on page 20 of the attached.
https://www.mbta.com/uploadedfiles/About_the_T/T_Projects/T_Projects_List/Executive_Summary.pdf
The only portal width dimension I can find for Silver Line Phase III is for the Columbus Ave portal. It is listed at 34ft wide.
https://www.google.com/maps/@42.3757547,-71.1188835,177m/data=!3m1!1e3?hl=en
https://www.google.com/maps/@42.373...h5Cfbiuj_D3WunPC2u2A!2e0!7i13312!8i6656?hl=en
The Harvard Square bus portals also are less than 50ft. For what its worth the Silver Line Way portal at D street scales to about 45ft on Google Earth.
It's 50 ft. But if you want to play scaling games on Google Earth you better be prepared for Ave de Lafayette to have a fudge factor that subtracts 5 feet too.
It is also...like a broken record...utterly irrelevant to feasibility. Once more, for emphasis:
City of Boston Fire Prevention Code said:
Section 7.09 — Access for Fire Department Apparatus and Personnel
(b) Approved hard-surface, all-weather, access fire lanes, not less than 20 feet in width, for use of Fire Department apparatus, shall be provided to within 25 feet of any building or other structure at the site.
You can check Livablestreets for corroboration of the fire code, as they have a long write-up about the mechanics of doing bike-friendly and ped-friendly infrastructure in Boston that attains full design compatibility with the word-for-word above cited emergency response regs. That blurb of legalese quoted here is not some eye-of-beholder verbiage one can interpret any way they please. It is a very specific and well-enumerated part of the design for any building-street interface and any civilly engineered public infrastructure touches.
No portal location whatsoever allows for fire dept. access within 25 ft. of 11 Ave de Lafayette or the emergency egress on the tower within the maximum allowable 6% grades for a BRT incline. None.
No permit...game over.
ADA sidewalks must
each be no less than 5 feet wide when they are placed 2 or more feet from a curb or barrier. (source: AASHTO and FHWA regs...multiple wikis online enumerating this with diagrams). ADA sidewalks directly abutting a curb or barrier must be
no less than 6 feet wide.
As this will be an abutting-barrier situation with immovable building egresses on both sides of the street, you do not have 6 feet on both sides of the road to provide ADA-compliant building access.
No permit...game over.
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Harvard bus portal was built as trolley tunnel in 1912, converted to dual-use busway in 1938, and reconfigured at the north portal in the late-70's with air rights cover-over at the south portal late-80's. Its width is grandfathered to 100 years ago, lacking the emergency tunnel egresses and car-blocking protections required today for the Silver Line. It is a completely irrelevant comparison.
Again...these portal safety specs were fully explained not 5 posts ago.
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Columbus Ave. portal was rejected. It was the preferred alternative for neighborhood groups, but got thumbs-downed on engineering feasibility. Maximally steep grades combined with minimally narrow width required to fit it within that block induced a schedule-killing speed penalty. As this is exactly what you are facing on Ave de Lafayette to try to skirt the legal no-go's, 34 ft. wide @ 6% steep is not an aspirational reference or possible escape hatch for AdL. It's a great big flaming red flag that you're wasting your time with something that paid project engineers have already determined has project-wrecking infeasibility and makes for bad-performing transit.
"Charles Street Modified" with a portal at the Tremont/Marginal traffic island was the last candidate left standing at time of cancellation. The same alignment that's an arrow-straight shot from the covered-over Pleasant St. trolley portal via the widest, least-impactful street corner to tunnel to. Go figure.
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Not one of these AdL rebuttals addresses the two very real and ironclad legal blockers to a construction permit. The design either solves those two issues head-on and in totality, or there is no build. No amount of fussing around the edges re-presenting the same plan of 0.0001% feasibility odds gussied up with slightly different periphery factoids gets any closer to earning that construction permit. It still whiffs on the permit by a mile.
Either there's a radical design/alignment change making a quantum leap into total legal compliance here, or continuing to septuple-down on Ave de Lafayette out of stubbornness just ends up proving the definition of insanity through repetition.