Re: I-90 Interchange Improvement Project (Allston)
Allright, at Harrys suggestion I've removed all connections to the existing street grid. While I personally believe the streets should be extended, that's a battle for another day, and would be better served after some discussion/education. Babcock still needs to be extended through to Western Ave for traffic flow.
I've added some more bike and park connection benefits to try to get the parks/bike people liking this idea. Strong allies for a difficult proposal. Most notably are cycle tracks on Cambridge St, but I also added the Grand Junction path idea as well as a stronger visualization of the connection at Pleasant Street.
I also (hopefully) made the graphics more clear and concise. At others suggestions I reconfigured the interchange so there are less grade changes on the steep curves, I also think it will be easier to build. The CR over the Pike has been reduced from four tracks to two, and I made the CR yard a very apparent not likely option, with labeling as such. Also, while driving on Lincoln Street the other day, I realized if it was to be extended it would make infinitely more sense to do so as an underpass beneath Cambridge Street than somehow rising up to meet it at grade. This would require the bridge reconstruction project to be merged into this one, but that should have been happening from day one anyway.
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I now understand what you were doing with 19B and Babcock St. Though I am very skeptical that BU will embrace turning Babcock St into a major connector street. I would think BU views that area around Babcock and Ashford as its last contiguous chunk of developable land. (All Boston schools (except for Harvard and Allston) are land-poor.).
Babcock as I have it proposed is one way southbound, and only the traffic bound for Allston or Brookline would get off there (I didn't highlight it, but I would suggest a left turn restriction at Comm Ave to keep people from using this exit for Fenway access).
With 19A, its not enough to say 'its not worse than what's there presently', because it is worse. You have re-routed west-bound Storrow / Soldiers Field Rd away from the river, and it appears the only reason for doing so is to create park space.
I've addressed this before, but just to clarify, opening up land for an expanded park along the river is just a really great benefit. It takes a lot of room on this diagram because I am trying to get the bike/parks/NIMBYS on my side for this, and more parkland is a great way to show a real tangible benefit.
The reason for rerouting SFR away from the river is to reduce the massive clusterfuck that has been created by having everyone going to or from Arlington, Cambridge, Allston, Brighton, Brookline, East Watertown, and god knows where via the Pike have to use a tiny section of Cambridge Street. It causes the intersection by the double tree to be a disaster 20 hours a day. It causes retarded amounts of cars to cram through Allston's Union Square, Linden St, Harvard Ave, etc.
The only way to alleviate this is to distribute all the traffic instead of concentrating it at one point. So your two options are to build a gigantic spidering system of ramps, exits, and interchanges (inner belt, part 2), or use existing infrastructure. Soldiers Field Road west of Cambridge Street is humorously under capacity, and is perfectly poised to do this. But with it crammed right against the river there is no way to build an interchange with the Pike while still allowing through traffic from SFR to Storrow.
So, by using the existing alignment of the exit 18 ramps, plus a small easement through Genzymes parking lots, you fix all these issues, PLUS get 500% more parkland along the Charles River, a massive upgrade to the bike path, and less traffic in, around and through Allston.
That is worth the money.
Its unnecessary from a traffic flow standpoint, and it greatly complicates the 19A flow regime because of 19A's cross-lane flow (crossing Soldier's Field westbound traffic) from a left entrance to a right exit.
But not all cars will be doing this, as per my previous point. Only cars bound for Allston proper and Central Square will be taking Exit 1 off of SFR. The rest will stay on SFR further north/west. You are confusing the current configuration of ALL traffic (Allston, Brighton, Arlington, Cambridge, Storrow, SFR, East Watertown, etc) dumping off here, with only a fraction of that volume.
I freely admit this is not a 100% perfect configuration from a traffic engineering standpoint. But that's the whole point. Only being concerned with throughput is the reason this project is happening in the first place, it created a disaster for everyone not on the interstate. My proposal is a balance between the needs of highway users with those of the local road network, development potential, and parkland reclamation.
From an analysis standpoint, your scheme would benefit greatly from elevation profiles, at least for the major alignments. My belief is that the reconstruction of the Allston interchange will need to comply with current Federal standards for interstate highways, standards which may be quite different from when the Pike was designed more than half a century ago.
Getting paid for this would greatly benefit me having the time and resources to create them. Unfortunately, my computer has heat issues and I am neglecting my personal and professional work to get this done. I've been consulting the standards and attempting to apply them wherever possible. The lane widths are all correct, and the grades are vastly improved this iteration thanks to our previous discussion. The curvature of the ramps is restrictive, but less so than the brand new interchange they built by North Station.
The entire eastern end of your proposed configuration seems to be driven by the Grand Junction railroad, and facilitating x number of train movements a day over the Grand Junction. So to create a wye for the Grand Junction, the Mass Pike needs to be put 20? feet below its existing grade between Mountfort and Commonwealth, which crudely looks to be about a new 10 percent grade.
And because of the now depressed elevation of the Pike under and just west of Commonwealth Ave, eastbound Storrow would need to begin climbing in grade from about your Babcock St extended to where it diverges away from the Pike. Exit 20 is eliminated, because the Pike has to be so depressed immediately west of the BU bridge to allow for the wye, and for eastbound Storrow to cross above it.
Why do you need four railroad tracks from what is essentially Buick St. west?
It was a typo, there were actually only 3 tracks, and now there are two.The wye was an experiment I forgot to take out, I don't think it would have worked anyway. Although, the Pike is already below grade at Comm Ave, it rises after that. I'm just keeping it down.
Do you intend the Cambridge St and Western Ave bridges over the Charles to be two-way?
They aren't now, and changing that would royally screw up the entire traffic flow pattern from the river to Central Square, as well as the street rebuilding project they are just finishing up. This is why the one way pair ofBabbock Street and Stadium Way running from Western to Cambridge is so imperative, they supplement Pleasant St for cross-traffic. Currently the frontage road in front of Genzyme is a disaster because it is the only practical way to go from one one-way bridge to the other after N. Harvard St.
