Re: I-90 Interchange Improvement Project (Allston)
How insanely expensive would it be to have the track drop below grade for the Mass Ave crossing?
We've been through this umpteen times before. It can't be done.
-- You don't have enough running room to drop the tracks 17 ft. in elevation between Main St. and Mass Ave. at RR grades when safe braking distance around crossings and that curve right underneath the air rights property is factored in.
-- You can't start the incline anywhere else because the Red Line tunnel crosses under Main. Trying to slip under Red would create a tunnel so deep it would have to start between Medford St. and Cambridge St., be much more expensive than regular subway cut-and-cover because RR cars are so much taller than LRT and HRT, and be impossible to ventilate the diesel fumes without the Kendall platforms turning into the Back Bay platforms.
-- No exceptions. The line carries freights and T/Amtrak non-revenue push-pulls several times a day without time separation, and is part of the common-carrier rail network. Therefore construction has to comply with ALL the rules of the common-carrier rail network. The DMU's, being FRA-compliants, likewise have to comply with all those rules all of the time.
You could probably eliminate every single crossing except Main on LRT with the much steeper grades trolleys can climb. Overpass, like they'd certainly do on Mass Ave. in any BRT/LRT UR configuration, or just graft the trolleys or buses onto a regular road light cycle at Main and Broadway. So if it's THAT big a deal to have no crossings...get the real thing done and converted to trolleys. 20 more pages of Crazy Transit Pitches trying to find some precision tactical nuclear strike at unlimited billions that makes DMU's work is a waste of time.
F-Line, you make it sound like DMUs on the Grand Junction will bring about Armageddon in Cambridge traffic. Maybe so if there were massive slow-moving trainsets every 15 minutes... but, unless my picture of a DMU is mistaken, I visualize a small trainset moving like a trolley across a street, without the need for gates or bells. Probably just a new signalized 'intersection.' Am I wrong? For example, does the FRA require the gates and bells when a DMU crosses at grade?
If it just requires a traffic light, I don't see the harm here. Cambridge has done all sorts of new traffic signals on Mass Ave in the last 5 or 6 years. Some have hurt and others have helped, but each of the changes have been quickly absorbed. Each of those changes were a lot more impactful than a single light turning red every 15 minutes would be.
Incorrect. FRA-compliant DMU's ≠ trolleys. To run them through here the gates would have to go down the same way they do in advance of a freight train. Signal preemption can give Mass Ave. a longer green to clear a queue
after the gates go back up, like they were planning to do with Worcester-North Station service. But it doesn't stop the gates from going down for exactly the same amount of time before/after a train passes. You have to get those tracks off the FRA network to stick an actual light cycle onto the ROW, and that's only doable with LRT or BRT.
They did all this traffic modeling in the first study.
-- Speeds on the tracks have a low ceiling because of the sharp curves, and particularly the sharp curves coming off the Worcester Line and Fitchburg Line junctions. And the poor sightlines at the Main St. crossing. Probably not topping 35 MPH track speed on the longest straightaway, and slower at the bend in the middle. You could repair the line to HSR maintenance standards and this wouldn't change...the GJ is basically an elongated version of the New London Station area on the NEC with much worse traffic on the crossings.
-- Any vehicle that's running nonstop off BU Bridge will hit Mass Ave. at the same (low) top track speed. So for purposes of the Worcester-North Station study done around nonstops the push-pull math for gate time at Mass Ave. is the best-case and unchanged from what it would be if the DMU were making the nonstop, if an EMU were making the nonstop, if an Acela were making the nonstop. Just multiply # of gate events by the study math to tally up the lower bound of disruption for all-day service (it's real ugly).
-- Add a station stop near Kendall and the any-train is going to be much slower crossing Binney, Broadway, Main, and Mass Ave. vs. an any-vehicle nonstop. Obviously a DMU would do better in/out of a dead station stop than a push-pull, but it'll still be considerably worse than a nonstop. An M8 or Silverliner EMU can't accelerate
that fast to avoid a lengthening of the gate disruption at Mass Ave. Stop vs. nonstop is the difference-maker, not vehicle type. This is the outer performance limit of a retrofitted RR being a viable solution over real LRT/BRT conversion.
Yeah, but street running LRT isn't, and that's basically what this would be. We're not talking about mile-long freight trains here.
DMU lines in other cities cross major streets:
Austin:
https://www.google.com/maps/place/N+Lamar+Blvd+%26+Airport+Blvd,+Austin,+TX+78752/@30.337741,-97.7189608,797m/data=!3m1!1e3!4m2!3m1!1s0x8644ca3633f6b3a3:0xb5022defdcbad184
Beaverton, OR:
https://www.google.com/maps/place/SW+Canyon+Rd+%26+SW+Lombard+Ave,+Beaverton,+OR+97005/@45.4888705,-122.8012561,648m/data=!3m2!1e3!4b1!4m2!3m1!1s0x54950ea09365661d:0x2b6cd5c0020a1f2
Trenton:
https://www.google.com/maps/place/S+Broad+St+%26+Elmer+St,+Trenton,+NJ+08611/@40.2095236,-74.7551249,706m/data=!3m2!1e3!4b1!4m2!3m1!1s0x89c159bf17b46beb:0xd086cea8d4ff2f9b
Spurious comparison. The FRA-compliant DMU's are like a heavier and slightly clumsier M8 or Silverliner EMU, not one of those RiverLINE or Austin DLRV's. The RiverLINE does deviate off its RR ROW and run short segments on modified streetcar trackage with turning radii way too tight for a RR car. That's one of the reason why those types of DMU's have been much more successful so far than FRA-compliants: there's more bleed-through into LRV-like behavior and mix-and-match. That's the upside of the FRA exemption. The downside is...you can only apply it places where you don't have to intermix. And it's a spectrum of tradeoffs even wholly within the FRA-exempt category, where there's a balance between lower-capacity cars that can do more of the street turning radii vs. higher-capacity cars that do less.
Those examples don't work here. Worcester Line and North Station are shared commuter rail traffic. The Grand Junction has multiple daily push-pull equipment moves and a freight round trip. And the BET/North Station area has all-day freight. There isn't a single place on MBTA commuter rail or its non-revenue spurs where time exemption is feasible. So all those DLRV's and all hybridization of LRV-like behavior are off the table. If it doesn't work without bending it to more LRV-like behavior such as holding the gate timings to different standards for only one vehicle...it's over. Queue-clearing times at the crossings were well-established for the max track speed of any vehicle running nonstop. Add frequencies, add queue-clearings. Add stops, add extra time for each queue-clearing no matter what vehicle you're running. There's no loophole for fudging those differences with FRA-compliants if it remains an FRA railroad running in mixed RR traffic. It is what it is.
