So, you're proposing that for this trip, which takes under 30 minutes under current T schedules even accounting for the extra stops and not counting the improved acceleration and dwell times of DMU vehicles, you will not only need to backstop both ends of the line (and hence assume that EVERY SINGLE TRAIN will be late, since a 15-minute headway can be done by 4 pairs in motion at all times), but that backstop will need to itself be backstopped because not only is every train going to be late but delays will routinely exceed 15 minutes? Sorry, dude, that's a really generous assumption to give yourself. I'm not saying that every train will be on-time, but there's simply no reason that the inbound train can't either pick up passengers, turn around, and go, or cover the next headway its late. Commuter rail passengers do have the expectation that their train will sit on the platform for a half-hour before it leaves, but their expectations would have to change.
Oh, quit twisting my words. You are so evangelical about this a factual debate is almost impossible around here on the pros/cons of DMU's. Every damn time this gets discussed you get hot under the collar at other posters for raising legitimate doubts about the near- and mid-term prospects for DMU's. Can you please acknowledge that there ARE pros/cons and a serious stall in the advancement of U.S. DMU acceptance--and hence, purchase scale from unit cost--that significantly muddies the water on available options?
I am saying it is not clear-cut enough and not advancing fast enough to be clear-cut that you can say "book it...done" and write off other alternatives like electrification as too expensive or too far-future. It makes too many assumptions that the DMU market is going to immediately move
fast, when it shows few signs of that sort of momentum coming this-decade. Or busting out of its niche of single starter lines and airport dinkys. If you are so sure of your math, show us the math that proves the economics are going to snap into gear on the short-term timeframe. The available evidence and momentum does not allow for accepting that on assumption. And if you can't accept on assumption backed with evidence that it's going to be a this-decade certainty for fitting the economics...why are you so certain that an electrification option won't fit your timetable? We don't know what the timetable is!
If you don't want the possibility of putting up with crappy push-pulls for the next dozen years because the economics of something better isn't improving, why narrow the search for options? I'm not saying electrification is slam-dunk either. But putting nearly all your eggs in the DMU basket today and discounting all options is not smart when DMU's aren't evolving fast enough to market acceptance.
If you are disputing the fact that DMU's aren't ready today...educate us on that math because current conditions sure don't show it without a whole lot of wishful thinking.
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Re: the headway comment and delays...
That is not what I said at all. SS-BBY is capped at restricted speed for every vehicle because of all the crossing traffic...that being by-definition what "yard limits" are. And it doesn't improve until you're almost out of the Back Bay tunnel. Yes, it is going to take the
exact same 6 minutes to get between the terminal and BBY as it does today, and since speeds don't rise much until the tunnel portal the max possible savings to Yawkey is seconds, not minutes. It's 11 minutes from SS to arrival at Yawkey today. The best you are going to do under DMU's is closing all doors at Yawkey and being ready to depart at...the same 11 minutes. Your max potential time savings are the on-platform dwell. That gives you 20 minutes to cover 6 more stops with dwells.
There is no way you can cover that and make the next headway with so few vehicles. I don't even think 3 in motion covers it. Look at the Mattapan Line...2.6 miles and 6 intermediate stops between terminals at 5 minute peak headways running no more than 1 vehicle per track at any any given time (i.e. avg. 2 in motion, a third usually staffed and idling at Mattapan in the queue, and sometimes more in motion at hours when terminal crowding increases dwells). So...4 out of a 10-car fleet in active use for minimum-most service at its stated daytime headway on the shortest rail line of any kind on the system using the fastest-accelerating cars of any rail service on the system. And a trip takes...15 minutes?
You think 11 miles and 7 intermediate stations including high-dwell time Back Bay with a permanent and unimprovable travel time through heavily-trafficked yard limits using DMU's instead of a trolley will be achievable in 30 or less using the exact same number of trainsets? No. Not even close. And that's before we even get to the seating capacity issue and need for 2 coupled pairs as a rush hour baseline. Yes, you are absolutely beyond the limits of your fleet figures shorting it that much and will have to cover run-as-directeds with push-pull. Every day, several times a day. Regardless of on-time performance rate for the schedule. Variable dwell times will do that. And let's not forget...there are at least 3 overlapping services on this route: Worcester expresses, Framingham locals, and Riverside DMU's. Plus Amtrak at 10 Inland Regionals per day 2025 goal, a Lake Shore Limited, and a likely Boston-flank Vermonter in the future. Your schedule can't have such little equipment give to deal with the variability of a heavy-use line. Either pony up and buy the fleet that'll make that happen at considerably inferior price, or you must run headways that can accommodate a push-pull set at any moment to backstop the variability.
The math doesn't work without it. And also, since you seem to be under the impression that it takes like 5 minutes for a push-pull to get to freakin' 10 MPH between SS and BBY I'm not sure how you can justify a no-margin DMU schedule with multiple overlapping Framingham/Worcester push-pulls slotting between every 2-3 schedule slots. Of course, the difference between push-pull and DMU acceleration up to 10 MPH is so microscopic it isn't a consideration...the difference in vehicles is all about the 10-50 MPH acceleration. But let's run with your math here for argument's sake...it doesn't bloody add up with mixed equipment and a locked travel time for all services out to BBY.
Those numbers are accurate, but note the important role "seat only" plays in that sentence. The Sprinter trains you're about to mention achieve higher capacity in part by allowing people to stand. In any case, SMART's DMUs, like many others, have the advertised ability to trail 2 or 3 coaches behind them. Theoretically, the T could use existing bi-level coaches between the married pair of DMUs, or simply put a DMU on the front and train coaches behind. The acceleration and emissions benefits are muted somewhat in that scenario (which is what Tri-Rail in Miami does routinely), but they're still significant. Plus, your engine car is carrying passengers, upping your capacity.
Show me the DMU model available for current purchase that lets you use off-shelf coaches. Right now the only FRA-compliant models only allow you to buy custom lightweight DMU trailers from the manufacturer. Because those vehicles do not have the power to pull anything more. It is the same restriction that requires EMU's like the Silverliner and M7/M8 to only be compatible with Silverliner or M7/M8 dead trailers. They can only pull a push-pull coach at restricted speed in an emergency. Tri-Rail does NOT use generic coaches for its DMU line. It uses Colorado Railcar DMU's with Colorado Railcar unpowered bi-level DMU trailers designed only to trainline with its DMU's. It's all custom. Their push-pull fleet is a large contingent of Bombardier bi-levels 100% identical to our Kawasaki bi-levels...and those are total no-go with the DMUs' horsepower. You pay the unicorn-vehicle premium for the mode in any vehicle configuration. There is nothing available for purchase this decade that lets them use an off-shelf Rotem or Kawasaki CR coach.
Maybe there will be in the future...there is a neat EMU concept NJ Transit is considering from Bombardier that would allow 2 off-shelf coaches to be pulled by 1 single-ended bi-level power car (stuffed into an off-shelf Bombardier bi-level coach shell) at only slight acceleration penalty (still better than DMU) with loss of only 20 seats in the power car. And that can certainly spawn its own DMU variant if it proves successful. But even that easier-to-build EMU is years away, and given the sluggish adoption rate for FRA-compliant DMU's this pivots right back to the timetable question. Prrove with evidence the option is gonna be there on the timetable they want to implement it, or concede that this is not so simple and the preferred alternatives list has not narrowed at all.
Whoa, now this line goes to Framingham? I haven't proposed it going to Framingham. I think maybe 2 pages ago someone asked if Framingham was a realistic destination for a "Fairmouted" Line, and now you're grabbing that and running with it to inflate your demand. Assuming Framingham as your destination also conveniently eliminates the issue of platform geometry at Riverside, where there simply may not be room within the current station for a full CR platform.
Also not what I said, but feel free to twist away. I am saying that your probable ridership for a full-developed Riverside corridor is equal to Framingham's current ridership. The number of stops will be similar. And given the fact that this will be hard-pressed to keep 30 mins. or less with station dwells and that SS-BBY penalty your schedule's not going to be worlds of difference faster. It's 45 mins. today to Framingham skipping the Newton stops on slow 60 MPH track. If that track gets uprated to 80 MPH in a couple years so they can meet the PTC mandate it's probably more like 37-40 minutes to Framingham on a push-pull that skips all between BBY-Wellesley Farms. Nothing that covers Riverside-inbound will ever top 60 MPH because the station spacing is too close. That would be the same even on an EMU.
So the Framingham actuals are with virtual certainty going to converge on all fronts with your Riverside estimates.
This decade. Meaning...you better be prepared to backstop this thing with enough equipment to cover similar loads and a very tight schedule for covering the stated headways. The vehicle requirements are going to end up close to double what you're quoting. And that is rooted in math you can crunch today.
Anyway, I won't claim that single married pairs of DMUs can serve all of this demand, but I don't think we really know what the demand would be, given that the Newton stations haven't seen competent service in 60 years. Density would suggest higher demand than along the less-dense Riverside Green Line, but frankly density in that neighborhood suggests that we should be burying HRT underneath the ROW. The point of DMU service is to provide rapid transit headways and appearances in locations where rapid transit itself is unfeasible, not to replicate the capacity of a subway.
Burying is going to be very hard here because of the Charles basin. We've detailed at length the problems downtown. It's either Back Bay landfill or Charles silt until Newton Corner. Saturated, flood-prone mush much more expensive to engineer than the cleared ROW and Pike canyon would indicate. It's very different from building a Riverbank subway on the Storrow roadpack essentially above-ground with the tunnel roof covered in grass. Very different from burying the B or E reservation under a full contingent of city street storm drains abutted by bone-dry, flood-controlled basements. The chance to put an HRT line on the B&A died when the Pike took Tracks 3 & 4.
Otherwise the ridership IS there. It was there in 1945 when they proposed just that. You only have to look at the bus coverage on this corridor to see that. The criscrossing lines at some of these stops are some of the busiest on the whole system (and it is killer that a major bus hub like Newton Corner has no stop today because it would outslug all 3 other Newton stops...today). It is buttressed with multiple Pike express buses. And the 57 and 70 are carrying disproportionate load being all things to both flanks of the corridor from lack of rapid transit options (artificial lack, in the 57's case). Follow the bus routes. They are the surest sign of any for unmet demand, and every rapid transit or quasi rapid transit line that sorely needs to be built (GLX, Blue-Lynn, Orange-Rozzie, UR, E restoration) has its path traced by above-normal clusterings of busy bus routes.
So what are you arguing against, now? You've expanded the range of your argument to assume that the T would have to buy inflated numbers of DMU vehicles for each of 4 or 5 lines simultaneously, in a single order, without phasing or testing the concept. You're comparing DMU service, which the T could roll out in 2 years if they chose to release an RFP tomorrow, to electrification, which there's no evidence the T is planning to do anywhere other than the NEC and will take 25-30 years to build, at fairly astronomical cost given it involves replacing EVERY LOCOMOTIVE THE T OWNS. You're arguing that buying the rolling stock to cover these headways costs a bunch no matter what mode we choose, so we might as well buy more locomotives (remember, DMUs can trail coaches) which are unsuited for the service, cost more to maintain, more to fuel, and cause more damage to the environment when their power is wasted pulling 4-car consists? And all because 3 decades down the line we might electrify the system and make all the current engines obsolete anyway?
And you are putting a whole lot of words in my mouth. Which is why this debate
never goes anywhere when the current state of DMU-land is discussed.
Dial the evangelism back a notch.
I'm not going to argue EMUs are bad. They're excellent technology. If in 50 years that's what's running on these lines - awesome. But they aren't going to provide the service these corridors deserve in a reasonable timeframe, which means this simply isn't the either/or you think it is.
And all I'm saying is what's the Plan B if DMU's are nowhere near ready by end of this decade? Push-pull forever? Do an egregious overpay that's gonna scale exceedingly poorly at that unit cost to the fleet they need? Wait however long you think it'll take to string up wires?
What is it...other than assumption the DMU market is going to snap into gear with momentum that shows no signs of near-term materializing? You seem to think something's gonna break soon. So what is it? Substantiate.
