by RenegadeMonster
I'm pretty sure they have managed 3 trains in 10 minutes At Salem when they were running off schedule due to a train being behind schedule. Two in one direction and the other in the opposing direction.
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BostonUrbEx wrote:I never suggested scrubbing GLX today. I'd say it should have been planned differently from the start, decades ago!This is even more disingenuous! The "Beyond Lechmere Northwest Corridor Study Major Investment Analysis" from 2005 quite literally scored LRT, BRT, and commuter rail modes against each other and crunched all the demand numbers in the appendices showing point-blank where native Somerville ridership does and doesn't get dispersed downtown. The existence of magical 1998 alternate-universe NSRL ribbon-cutting does not flip the travel patterns on their head from the Central Subway to the Waterfront/South Station. The CTPS data reaffirmed 100 years of established travel patterns on this corridor: they pour into Lechmere and go to Haymarket, GC, Park, and the stations along Boylston St. in huge numbers in addition to North Station. They even re-crunched the numbers based on presence of the Urban Ring changing the spread of linked trips around Cambridge, and it simply reaffirmed the original conclusion.
I'm not convinced. Salem has inbounds scheduled within 10 minutes of each other while utilizing diesel locomotive-hauled sets, a track/signal system that could be improved, and all on a single track pinch point. There is a point in the day where Salem sees trains every ~8 minutes (including both directions, but remember this is single track, so with opposing moves that's even more impressive). Not to mention, the discussion at hand involved quad-track.And this factoid artfully tapdances around the key-most point I made. Mainline rail can absolutely pack headways close. It cannot, because of the more heterogeneous traffic profile (that gets MUCH more diverse post-NSRL when scaled to the Lowell Line), guarantee that every Urban Rail local throughout a given shift sticks as close to the advertised headway as a closed metro/tram system can. A longer-distance train is going to get more schedule padding on a slot, and will clip and shift the margins of that MU schedule by a couple minutes a couple times an hour. That puts schedule consistency outside the margin of error a metro/tram system would be able to hold.
RenegadeMonster wrote:I'm pretty sure they have managed 3 trains in 10 minutes At Salem when they were running off schedule due to a train being behind schedule. Two in one direction and the other in the opposing direction.OK. Now take that one isolated example, even it up so inbound frequencies direct-match outbound frequencies around the tunnel and that single-track platform, and hold to that headway for every trip for 3 straight hours of each peak period 5 days a week. Hold that frequency for inside-128 locals through every slot that has to take a Newburyport/Rockport terminating in the outskirts of Essex County, every skip-stop trip, every train meet with the Western Route at Reading Jct., and traffic priority at Tower 1 and FX interlockings.
BandA wrote:Does heavier railroad equipment have longer stopping distance than trolleys?Uhh, yes. Absolutely. And it's not even close.
BandA wrote:I asked the T a couple of years ago why the GLX wasn't attached to the Orange Line instead of Green. Would have been simpler & the rolling stock is cheaper, higher capacity & lower dwell. They responded that the GLX was already planned & permitted so it was too late to change.Meanwhile I've asked that same question and been told that it would dilute Oak Grove frequencies too much.
Bramdeisroberts wrote:Other than that, you're right about the GLX being better as the OLX. For the price of the stations that the Time is already building, there's no reason why it SHOULDN'T be serving 6-car heavy rail trainsets that as you said eviscerate an LRV when it comes to speed, capacity, and dwell times. Furthermore, 3rd rail electrification is cheaper to install than catenary, and aligning an OL spur from between Community College and Sullivan to the NH route via the yards would be easier than relocating Lechmere, etc, with the added benefit of not setting off the NIMBYs in Brickbottom.Somerville has recovered from just as bad of a reputation as the other end of the Orange Line. That is seriously not a concern.
The only reason I can think of for why it ended up being green vs orange was again the NIMBY factor. The Orange Line has always had a certain, uh, reputation given the sorts of rougher neighborhoods that its southern end historically traveled through. If you're selling a rapid transit extension to a somewhat skeptical community that is already going to completely transform neighborhoods when it adds $100k+ of value to each and every home within a couple miles of it on the day it opens, it helps when you can sell it on connecting those communities to happy, friendly things like The Public Garden, the MFA, Back Bay, Newton, and Coolidge Corner, rather than Ruggles, Roxbury Crossing, and Jackson Square.
BandA wrote:Isn't the Green Line Central Subway just as overcrowded as the Orange Line?Yes, but in a way that the GLX complements. The existing Green Line mainly brings passengers in to downtown from the west, the GLX will mainly bring passengers in to downtown from the north (RR east?). Basically instead of turning around downtown and running mostly empty back west, Green Line trolleys will instead head up to Somerville to pick up more passengers. This doesn't significantly increase the load on the Central Subway, and in fact might actually ease the load somewhat, by reducing dwell time eaten up by terminating trains downtown (as I understand it, B trains will still terminate at Park or GC, but D trains will run to Medford). The fewer trains that have to dump all their passengers and turn around, the more trains you can squeeze through.
BandA wrote:Actually, you could route it through Science Park, if a crossover can be built at North Station or Haymarket. You'd have to study the layouts.Malden, North Station and Wellington are the #3, #4, and #7 highest ridership stations on the Orange Line and all have over 10K weekday boardings per the 2014 Blue Book. Branching service south of these locations (such as between North Station and Haymarket as you suggest) results in degradation of service to these stations through longer headways. For example, if the minimum OL headway through the Washington Street tunnel/Southwest Corridor is 5 minutes (estimating here, I don't have the actual # handy), then the minimum headway that could serve the Oak Grove branch is 10 minutes if the branch split is 50/50. Given these constraints, the only way to get a lower headway for Oak Grove is to make weight the split in favor of Oak Grove service, which in turn lengthens headways in the GLX corridor.
This is probably moot, something they can do in 20 years when they replace the Type 9s or have a shortage of trolley equipment.
Isn't the Green Line Central Subway just as overcrowded as the Orange Line?
GLX Impact on NH Route (Lowell Line)Thanks to the admin for the reminder. As one who rides the NH Route daily, it's going to be interesting to document here.
Postby Diverging Route » Mon Oct 27, 2014 7:12 am
This weekend the first visible impact of the Green Line Extension occurred on the NH Route (Lowell Line). So I thought I'd start a new thread to document progress and changes - which will be numerous over the next five+ years.
Nighttime Construction Advisory
GLX Early Work Continues Along the Lowell Commuter Rail Line
Work continues along the railroad [Lowell Line] right-of-way in the vicinity of the Colby St and Burget Avenue neighborhoods in Medford.
On Friday, November 10th, work crews will enter the right-of-way adjacent to College Avenue and will continue working through the start of service Monday morning, November 13th. The purpose of this work is to complete the cut-over of track along the retaining wall north of the College Avenue Bridge. Construction activities will require the use of heavy equipment such as front-end loaders, back hoes, dump trucks, generators, air compressors, and construction lighting.
The GLX Team apologizes for any inconvenience this work may cause, and has instructed work crews to minimize impacts to the community. Similar work hours and activities are anticipated for the weekend beginning Friday, November 17th through Monday morning November 20th.
Arlington wrote:OK everybody! We're back to the exact topic of this thread: the GLX's construction work's physical and operational impact on the Lowell Line, with news about the next two weekends' worth of work from MassDOT.Not exactly true. If you read the statement, there are two weekends planned. The MBTA has not released any information regarding busing next weekend at this point nor does this release indicate anything (although admittedly it looks like a neighborhood noise advisory). Based on your picture on the previous page of the thread and the fact the release talks about two consecutive weekends, my guess is that they are throwing the mainline track to line up to the new crossovers, one track each weekend. This would allow service to continue on the track not being worked.
As on recent weekends, the operational impact on the Lowell Line will be bustituted all weekend while crews swarm over the right of way in the area around Tufts U/College Ave. The physical impact is that by Monday the cut-over of the Lowell Line the new interlocking will be complete: