Seems with a likely permanent decrease in commuter rail ridership, single unit DMUs could be an alternative on some lines to the 6 car mostly empty norm, at least off peak? With the post covid "work from home" model likely usurping cubicles, DMUs could be an energy and money saver when social distancing is over.
Railroad Forums
Not happening anytime soon. As it has been discussed many times, they need at least 4 cars to be able to operate at normal speeds and brake properly. With fewer cars, they would need to operate at a reduced speed in order to properly brake. There is no shred of evidence anywhere indicating that they are purchasing dmu’s and when they proposed it a while back, it got scrapped. Also it is not cheap to swap cars in the yard. They would have to take the train out of service from south station to readville, swap the cars to their desired consists, perform brake tests every time, and then bring it to south station to start its revenue run with whatever trip it gets assigned to. It’s cheaper to run the sets as it is with opening whatever cars is needed to serve the customers as well as maintaining safe social distancing.
Long, long ago they used to run RDC's. As a young child, waiting for my mother and grandmother to finish shopping at Calvert's in Needham Heights (where Trader Joe's is today), I stood on the corner and watched as a single RDC crossed West Street, stopped, unloaded its passengers, and then retreated the way it came.
If they could do it back then, why not now? And why should the braking distance of a string of four cars be any different than that of a single car? Four times the mass and four times the braking force should stop in exactly the same distance, no?
If they could do it back then, why not now? And why should the braking distance of a string of four cars be any different than that of a single car? Four times the mass and four times the braking force should stop in exactly the same distance, no?
MU's (either E of D) can absolutely operate in shorter (1-3 car) consists, as has often been done with RDCs or various styles of EMUs on electrified lines. SEPTA for one still regularly operates 2 car married pair EMU by themselves. Is it possible that modifications to the signal system, or special design features be added to the MUs, to properly operate the signals, provide for proper braking, etc? Yes, but that's what design and engineering are for. Also, keep in mind that it's quite possible that a modern DMU might have very different braking systems versus a standard push-pull consist operating today.
It would be interesting to know if the brake tests and PTC tests needed for a set of xMUs when cars are added/dropped is much different than what is needed for changing ends at a terminal. Don't know if it's still practice, but I recall watching SEPTA crews routinely add/drop EMUs to make shorter consists for off-peak. The use of multiple-unit couplers makes the mechanical/electrical/air process very quick.
tl:dr - Lengthening/shortening xMU consists is a whole different animal from making/breaking push-pull consists.
It would be interesting to know if the brake tests and PTC tests needed for a set of xMUs when cars are added/dropped is much different than what is needed for changing ends at a terminal. Don't know if it's still practice, but I recall watching SEPTA crews routinely add/drop EMUs to make shorter consists for off-peak. The use of multiple-unit couplers makes the mechanical/electrical/air process very quick.
tl:dr - Lengthening/shortening xMU consists is a whole different animal from making/breaking push-pull consists.
Wondering if I'll see the Western Route double-tracking finished before I retire...
Photo: Melbourne W7 No. 1019 on Route 78, Bridge & Church Streets, Richmond, Victoria. 10/21/2010
Photo: Melbourne W7 No. 1019 on Route 78, Bridge & Church Streets, Richmond, Victoria. 10/21/2010
As someone who has lived many years of their life in place where DMU's with formations from one to ten cars run at speeds up to 100mph, with a safety record far exceeding any US railroad, I'm utterly baffled by the braking comment.
I know US passenger railroads are largely still stuck in the 1950's, but this "4 cars for braking" strikes me as a ridiculous comment.
I know US passenger railroads are largely still stuck in the 1950's, but this "4 cars for braking" strikes me as a ridiculous comment.
To my point
https://en.wikipedia.org/wiki/British_Rail_Class_197
They're even operated by Keolis. And could easily be assembled in Mass, the same way they are in Wales right now.
https://en.wikipedia.org/wiki/British_Rail_Class_197
They're even operated by Keolis. And could easily be assembled in Mass, the same way they are in Wales right now.
I seem to recall that one of the primary issues was needing DMUs that meet FRA specifications - and I recall only one US company that was even attempting to make them (Colorado), which produced only a small number for Florida I think - something like just 2 three-car sets. They shut down and the assets acquired by US Railcar, but don't know if they've actually produced any MUs since.
First Law of Public Transportation: You can never be early, but you can always be late.
Locomotive-hauled trains need at least 4 cars so that the braking force of the coaches can slow the locomotive. Note that this minimum consist length is a function of how the signal system is set up; New Mexico Rail Runner happily operates with 2-car trains much of the day. With DMUs, the braking force is the same regardless of how many units are coupled together; the problem then becomes how long does the train need to be to shunt the signal system.
"The destination of this train is [BEEP BEEP]" -announcement on an Ashmont train.
The only train manufacturer building DMUs in America today that is Buy America compliant is Stadler Rail in Salt Lake City.
Their FLIRT train has "alternate" FRA compliance. Worldwide, Stadler has sold over 1,500 trains (as of June 2018)
Presently Trinity Metro runs them on their TexRail service, operating it on shared tracks with freight trains using a time separation schedule but will operated them with FRA compliant passenger trains over the share tracks without locking out turnouts. It shares tracks with the Trinity Railway Express (TRE) FRA compliant trains in Fort Worth/ But it has built flyovers to avoid busy freight train tracks where time separation schedule could not work. And while Amtrak trains also visit downtown Fort Worth, the Amtrak trains and TexRail trains do not share the same tracks. With different floor heights between the various trains, the platforms height need to be different, hence using different tracks. DART plans to use the same trains with its Silver LIne, and so will the Arrow trains in the Inland Empire in Southern California with just two cars per train. Additionally, the last FLIRT trains being delivered to Arrow will have hydrogen capability in the power unit instead of diesel engines.
The DMU version of the FLIRT train can be a 2, 3, or 4 car version with a power unit installed between two of the cars in for all practical purposed permanently coupled or attached train set. the UK's Class 755 trains are very similar, the Class 745 is a 10 car EMU trainset without a diesel power unit. The DMU Class 745 trains run just like an EMU under a catenary. The East Anglia service thought they could easily separate the 10 car train set into two 5 car train sets for maintenance, but changes their opinion quickly after trying. They enlarged their maintenance building eventually to accommodate all 10 cars.
I'm not that familiar with MBTA commuter services where a DMU might make sense. But anytime you run short passenger trains on freight lines, careful attention is needed for proper shunting of any wayside signals. DCTA and CapMetro run 1 car Stadler GTWs, and both had shunting problems activating Various wayside signals correctly. But they are the masters of the railroad being used, so after significant effort they have been able to fix the shunting problem issues. That is something most freight operators will not do, they will instead insist upon a minimum number of axels in a train to ensure proper shunting of signals. So, short DMU trains in my humble opinion will only work on rail corridors owned by the transit agency providing the service. And at best, coupling two DMU trains together you could end up with an 8 car train set running in a multiple unit set.
https://en.wikipedia.org/wiki/TEXRail
https://en.wikipedia.org/wiki/Silver_Li ... d_Transit)
https://en.wikipedia.org/wiki/Arrow_(commuter_rail)
https://en.wikipedia.org/wiki/British_Rail_Class_755
https://en.wikipedia.org/wiki/Stadler_FLIRT
Countries where Stadler has sold FLIRT trains to include: Algeria, Azerbaijan, Belarus, Canada, Czech Republic, Estonia, Finland, Germany, Hungary, Italy, Netherlands, Norway, Poland, Portugal, Serbia, Slovenia, Sweden, Switzerland, United Kingdom, United States.
Although DMU and H powered versions are fairly recent.
Their FLIRT train has "alternate" FRA compliance. Worldwide, Stadler has sold over 1,500 trains (as of June 2018)
Presently Trinity Metro runs them on their TexRail service, operating it on shared tracks with freight trains using a time separation schedule but will operated them with FRA compliant passenger trains over the share tracks without locking out turnouts. It shares tracks with the Trinity Railway Express (TRE) FRA compliant trains in Fort Worth/ But it has built flyovers to avoid busy freight train tracks where time separation schedule could not work. And while Amtrak trains also visit downtown Fort Worth, the Amtrak trains and TexRail trains do not share the same tracks. With different floor heights between the various trains, the platforms height need to be different, hence using different tracks. DART plans to use the same trains with its Silver LIne, and so will the Arrow trains in the Inland Empire in Southern California with just two cars per train. Additionally, the last FLIRT trains being delivered to Arrow will have hydrogen capability in the power unit instead of diesel engines.
The DMU version of the FLIRT train can be a 2, 3, or 4 car version with a power unit installed between two of the cars in for all practical purposed permanently coupled or attached train set. the UK's Class 755 trains are very similar, the Class 745 is a 10 car EMU trainset without a diesel power unit. The DMU Class 745 trains run just like an EMU under a catenary. The East Anglia service thought they could easily separate the 10 car train set into two 5 car train sets for maintenance, but changes their opinion quickly after trying. They enlarged their maintenance building eventually to accommodate all 10 cars.
I'm not that familiar with MBTA commuter services where a DMU might make sense. But anytime you run short passenger trains on freight lines, careful attention is needed for proper shunting of any wayside signals. DCTA and CapMetro run 1 car Stadler GTWs, and both had shunting problems activating Various wayside signals correctly. But they are the masters of the railroad being used, so after significant effort they have been able to fix the shunting problem issues. That is something most freight operators will not do, they will instead insist upon a minimum number of axels in a train to ensure proper shunting of signals. So, short DMU trains in my humble opinion will only work on rail corridors owned by the transit agency providing the service. And at best, coupling two DMU trains together you could end up with an 8 car train set running in a multiple unit set.
https://en.wikipedia.org/wiki/TEXRail
https://en.wikipedia.org/wiki/Silver_Li ... d_Transit)
https://en.wikipedia.org/wiki/Arrow_(commuter_rail)
https://en.wikipedia.org/wiki/British_Rail_Class_755
https://en.wikipedia.org/wiki/Stadler_FLIRT
Countries where Stadler has sold FLIRT trains to include: Algeria, Azerbaijan, Belarus, Canada, Czech Republic, Estonia, Finland, Germany, Hungary, Italy, Netherlands, Norway, Poland, Portugal, Serbia, Slovenia, Sweden, Switzerland, United Kingdom, United States.
Although DMU and H powered versions are fairly recent.
Many moons ago and technology has evolved. That said, when the B&M, and NH etc incorporated RDC's into their freight heavy ROW's, what adjustments in signal and brake systems did they alter and if they did, is there anything that could be applied to DMU integration into modern railroads?
One other set of initials was left out -- NYC. Practice had become to run single RDCs in local service on the B&A. One such single-RDC local had sanded itself to a stop at Palmer. The sand separated the wheels from the rails so no shunt. A freight didn't get a Stop and ran into the RDC with 1 or more fatalities. The full deets are somewhere in the ICC archives for the mid-to-late 50s. 2-unit trains became the new practice, as was pulling ahead from a sanded-stop point to assure shunting.
To follow up on some other points, adjusting train size to suit off-peak demands means labor -- even with mass-transit-style coupler/mu boxes. It also means storage yards are needed. Mass-transit-style couplers/mu boxes also need similarly-equipped protection/recovery power.
The more complex an item is, the more failure-prone components that item has. The B&M's experience with its aging Budd fleet should be more than ample warning about seeing the answer to all problems in a new technology.
To follow up on some other points, adjusting train size to suit off-peak demands means labor -- even with mass-transit-style coupler/mu boxes. It also means storage yards are needed. Mass-transit-style couplers/mu boxes also need similarly-equipped protection/recovery power.
The more complex an item is, the more failure-prone components that item has. The B&M's experience with its aging Budd fleet should be more than ample warning about seeing the answer to all problems in a new technology.
"A gray crossover is definitely not company transportation."
In the joint MassDOT/MBTA FMCB meeting earlier this week, spring service changes were brought up, and there was some discussion of adding MUs, and it was brought up that consists will be shortened when the schedule changes occur in April. Obviously any MUs would be a longer range change.
jaymac wrote: ↑Thu Feb 25, 2021 10:51 am One other set of initials was left out -- NYC. Practice had become to run single RDCs in local service on the B&A. One such single-RDC local had sanded itself to a stop at Palmer. The sand separated the wheels from the rails so no shunt. A freight didn't get a Stop and ran into the RDC with 1 or more fatalities. The full deets are somewhere in the ICC archives for the mid-to-late 50s.I looked this up and found a PDF here: https://www.jonroma.net/media/rail/acci ... c/3547.pdf
Interestingly, the specification for sander output was to output 3 pounds, 1.4 ounces of sand over 3 minutes, but the accident RDC released 74 lbs, 3 ounces over 3 minutes in post-accident testing.
That incident cause the end of single RDC trains, IIRC. I know the B&M put a stop to them.
Rockingham Racer wrote: ↑Thu Feb 25, 2021 1:51 pm That incident cause the end of single RDC trains, IIRC. I know the B&M put a stop to them.The New Haven, PC, and Metro-North definitely kept running single RDCs well after that, so it wasn't a universal change.