It sort of does, because the easiest UR build would've been to plunk LRT/BRT on the existing bridge and move the Eastern back 100 ft. south to a straighter/shorter fixed bridge on the old Draw 7 alignment (since RR must land on the Everett shores on south half of ROW to accommodate the Everett Jct. freight turnouts). This footbridge gets in the envelope. Not fatally, but somewhat problematically. But not sure it's worth worrying about because (as in previous post) these grades are a lot steeper than they truly need to be to accomplish the job--and the grade is direct-exacerbated by the curve. So I somewhat doubt this is anything close to a final design since there are multiple different ways of doing this with less punishing rise.I dearly wish we were building a bike-ped-lightrail bridge (like Portland Oregon built).
I guess this one at least doesn't rule out F-Line's idea of a GL/UR bridge on the upstream side.
FWIW...the renders accurately depict how over-provisioned the '89 rail bridge is for spacing. Wide, wide track spacing and big fat emergency sidewalks the whole length of each side of the span. Most of that overprovisioning back in the original build was for Pan Am freights, because the utter gimp power they ran to Everett was so stall-prone over the peak grade that everything got overbuilt contingent on a crew being stranded near the tip of the navigational channel, having to put the whole train in emergency brake, and getting out to inspect on-foot before restarting. 3 decades ago it was their wet-noodle power 50-year-old GP9's that were the stall risk; today their GP40's assigned to Boston are intrinsically much brawnier, but just as old and decrepit at 48+ yrs. and liable to crap out by looking at it funny. Any company that ran like they gave a crap about finishing a schedule they started wouldn't be stocking such gimp power for a run through the middle of the commuter rail nerve center, and this wouldn't be a problem to begin with. But PAR, as we know, is not just any company. Fortunately/unfortunately they DO have a huge new influx of way newer/brawnier early-90's era CSX hand-me-down GE Dash 8's spreading through their power ranks. Only problem for Boston is that their biggest biz partners Norfolk Southern and CSX put the gun to their head to demand the non-gimp newer stuff on their big-revenue joint runs before anyone else gets the spoils, so Boston locals are still gerrymander-stocked with the oldest rolling ruins.
Were it not for that you'd be able to pack the tracks closer, and probably mash the two side sidewalks into one single-side double-wide bike/ped-worthy sidewalk separated from tracks by chain-link fence and have the path without needing to build any new spans. That, in a nutshell, is the logic of the LRT repurposing of the '89 span...you get a bonus path at no cost since the LRT tracks would be packed much closer, and making CR be the mode that changes spans sends it to over a more appropriately graded alignment for slightly faster RUR trips and no need for overwrought engine-stall precautions. It would be a good idea to at least *ask* if assessment is possible on re-packing the bridge, just on low odds that they get lucky on a favorable assessment and might be able to gain 'good enough' side path on a re-packed '89 span to gain the functional ped link without needing to build anything new. I'm fairly sure the answer is still going to be "No" because of the I.O.U.'s that Pan Am was given 3 decades ago for stall protection measures in the trade-over from the old draw to the replacement span. For all the years I've been following Mystic footpath talk (way, way pre-Encore) I can't recall any time the T was ever asked about those sidewalks on the span and how much overspacing was truly necessary vs. just a PAR-being-PAR hedge. Realism has to prevail, but asking point-blank wouldn't hurt on just the 0.5% odds of getting a lucky answer and maybe not having to build any new structures to accomplish this.
EDIT: To illustrate what I mean, the 1996-construction Neponset River CR bridge (itself a fixed-for-drawbridge replacement for the former draw span that burned down in the late-60's) has a slightly sub-28 ft. shoulder-to-shoulder width, while the 1989 Mystic Bridge is 33 ft. shoulder-to-shoulder due to the sidewalks. Both are officially-exempted from 1.5% max new-construction RR grades at 3% for Neponset and Somerville-side Mystic and 3% + fraction for Everett-side Mystic because they were both fixed-for-moving span replacements. Though CSX doesn't run any regularly-scheduled freight over their Neponset rights (then again, they also don't pussyfoot with woefully-maintained gimp power all places in MA where they do run). Main difference between spans is that the Neponset is arrow-straight with navigational peak near the center, while Mystic has the pronounced curve on the Somerville side and off-center navigational peak closer to the Somerville side. Not sure if the curve location exerts any role in the over-spread provisioning, or if you can simply chalk that up to a "Pan Am being Pan Am" provision.
So while you would not be taking any sort of luxurious-width path accommodations on a re-packed Mystic span with sidewalk fence-separated from RR it's dimensionally within the realm of feasibility to do on the as-is span if the advocates want to ask the point-blank question and fashion something sooner than any new span that by its wholly-new nature is going to be pricey. I suppose if you're going to be squeezing a 5 to at most 6 ft. width continuous sidewalk that you'd also be looking to dress up the length of the bridge with regularly spaced bulb-outs grafted on as structural overhangs so there's frequent-enough pausing/passing/lookout spots. But that's not a big production to swing because those wouldn't be load-bearing structures by any means.
Hey...can't hurt to ask. What's the worst that could possibly happen: "Can't do it because of X, and this bridge is different than Neponset's spacing because of Y & Z." Fair enough...move on to the next set of footbridge renders.