Greater Greater Washington

Transit


DMU trains are the DC region's missing transit mode

In the DC region we have Metro and commuter rail trains, with light rail, streetcars, and BRT all in the works. And of course, regular buses. But one common mode we don't have is DMU trains, which bridge the gap between light rail and commuter rail.


DMU train in San Diego. Photo by mrpeachum on flickr.

DMU stands for Diesel Multiple Unit. DMU trains are intended to operate on routes that look like commuter rail, but at almost light rail frequency. They go over long distances, with infrequent stations, usually on or adjacent to freight tracks. But instead of coming only at rush hour, trains come all day long, as often as every 15-20 minutes.

That's a great service model for suburban corridors that need something better than rush-hour MARC or VRE service, but are too far away for light rail and don't have the density to justify the costs of Metrorail.

DMUs, and their electric cousin EMUs, are used in Philadelphia, New Jersey, Portland, San Diego, Dallas, and Austin. They're proposed in even more cities.

One big advantage of DMUs over traditional commuter trains is that DMUs can operate on-street, like light rail. That makes integrating them with downtown areas much easier, because it frees DMUs to go anywhere, rather than only to a city's main rail hub.


Austin DMU on-street. Photo by paulkimo90 on flickr.

All MARC and VRE trains to DC must go to Union Station, because all the long distance tracks through DC go to Union Station. Not only does that constrain route planning, it's also a limit on capacity, because there are only so many platforms at Union Station. But a DMU could go anywhere.

There are not currently any plans for DMU lines in the DC region, but there could be. DMU would be a great solution for Maryland's proposed Charles County corridor or Fairfax's Route 28. Officials are looking at light rail for those corridors, but they're far out in the suburbs and wouldn't have very frequent stops, so DMU might be more appropriate.

In the long term it might also make sense to convert some of MARC and VRE's existing lines to DMU, or to supplement them with more DMU trains. That would give them more operational flexibility, and could increase service. But MARC and VRE are established as traditional commuter rail, and may be uncomfortable with anything else.

MARC and VRE also have to use tracks owned by freight companies. DMUs can be used in mixed company with freight, although that requires federal approval. But if the freight lines are already using their tracks to capacity, which is common in the DC area, then there's no room for more trains no matter what they look like.

DMU isn't Metro, and it isn't light rail. DMU trains can't do all the things those modes can do. It's not an appropriate mode where frequent stops are necessary. But for long corridors with infrequent stops and moderate capacity needs, it's ideal. We should keep in mind as we continue to advocate for new transit lines.

Cross-posted at BeyondDC.

Dan Malouff is a professional transportation planner for the Arlington County Department of Transportation. He has a degree in Urban Planning from the University of Colorado, and lives a car-free lifestyle in Northwest Washington. His posts are his own opinions and do not represent the views of his employer in any way. He runs the blog BeyondDC and also contributes to the Washington Post Local Opinions blog. 

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Totally. Stadler, which makes a DMU train called a FLIRT, expects to be able to run unmodified versions (i.e., without federal approval) within a couple of years mixed with freight. These cost a bit less than $2 million apiece, which is actually a bit less than what Metro is paying for its 7000-series cars.

Since much of the cost of rail transit is the tracks and purchasing the right-of-way, reactivating preexisting rights-of-way and abandoned tracks with DMUs could be a very cheap way to expand our rail network.

You forgot to mention, too, that DMUs can operate at top speeds of 125MPH (though would probably be limited to 79MPH around DC) and have pretty good acceleration/deceleration profiles.

by David Edmondson on Apr 9, 2013 12:37 pm • linkreport

I think that this characterization of DMUs is not quite right. DMUs are diesel self-propelled cars that can be coupled together to operate as one train. Maryland DoT used to operate DMUs on the Camden and Brunswick lines. These were commuter trains providing service similar to MARC's current service but with shorter trains owing to lower patronage at the time. The New Jersey line between Trenton and Camden uses DMUs that are essentially light rail but operate on a railroad line that (as far as I know) stills sees freight service when the DMUs aren't running. Depending on the design, DMUs can be light rail, commuter rail, even intercity. I don't think they're a distinct mode of transportation.

by Steve Dunham on Apr 9, 2013 12:49 pm • linkreport

There is minimal freight traffic on the VRE Manassas Line between Old Town Manassas and Alexandria (Connection to CSX).

If it was not for the VRE, Norfolk Southern would discontinue one of the tracks.

If a four track system were build between L'Enfant and Alexandria (Two Passengers/Two Frieght/Upgrade to the Long Bridge) there could significantly more capacity for an increase in service frequencies.

by jcp on Apr 9, 2013 12:51 pm • linkreport

Does Philadelphia have DMUs? I'm pretty sure they have EMUs (electric self-propelled).

DMUs can be used on freight lines but there has to be either time separation (they run during different set periods of the day) or separation using PTC.

eBART will use DMUs but on a little bit more upgraded corridor that could be reconstructed for BART heavy rail in the future. I don't think it will have street-running segments.

@Steve Dunham
The FTA's National Transit Database has created a new mode, Hybrid Rail, that encompasses these systems that use DMUs on rail corridors.

by MLD on Apr 9, 2013 12:57 pm • linkreport

Sounds like the old interurban railway. (1, 2)

by David R. on Apr 9, 2013 1:02 pm • linkreport

I have long proposed linking IAD with Manassas by rail so I would be interested to see how DMU would work on 28. Once you get to Manassas it is smooth sailing in either direction but it isn't clear how to get there. You can only take the 28 right of way so far so you would either need to run through park land or completely overhaul 28 south of 66. I don't see either approach being very popular.

by movement on Apr 9, 2013 1:09 pm • linkreport

DMUs would be great, and cheaper to run on the Camden Line, if additional tracks were added to free up space with CSX/ Until then we'll have to get by with slow ride that does not benefit commuters heading to Baltimore for work!

by CB on Apr 9, 2013 1:10 pm • linkreport

Drawbacks: DMU doesn't work underground, which would be likely in the DC core.

@MLD - SEPTA has EMU, no DMU but as Steve mentioned, NJTransit does on its Riverline from Camden to Trenton.

by Randall M. on Apr 9, 2013 1:23 pm • linkreport

Randall M,
Why don't DMUs work underground? I imagine ventilation must be part of the problem, but doesn't MARC run diesel engines through the tunnels up to Penn Station, and VRE and Amtrak through the tunnels up to Union Station?

by Mike B on Apr 9, 2013 1:25 pm • linkreport

@Mike B,
True, we do have diesel in the tunnels under 1st Street NE and Virginia Avenue SE / SW. I think the key is that they are relatively short distances.

That said, let's not forget the diesel isn't exactly environmentally neutral although the benefits of removing automobiles may make it worth it.

http://en.wikipedia.org/wiki/Diesel_locomotive#Environmental_impact

by Randall M. on Apr 9, 2013 1:43 pm • linkreport

@Randall M
Diesel Does indeed work underground. Diesel locomotives work in the Howard Street Tunnel, which is the longest under-city freight tunnel in the US. I am not sure what advantages DMU would have over DSU other than space savings in length of the train.

by Richard Bourne on Apr 9, 2013 3:31 pm • linkreport

I am not sure what advantages DMU would have over DSU other than space savings in length of the train.

Speed, acceleration, efficiency.

You can run transit service with DMUs, not just railroad service that wants to be transit-like.

by Alex B. on Apr 9, 2013 3:39 pm • linkreport

DMU's aren't a specific form of rail transit, they're just a type of equipment (like EMU's). SEPTA (Philadelphia) does not operate any DMU's, but relies exclusively on EMU's. (Even if they wanted to they couldn't because of emissions restrictions in the Center City tunnel)

Most DMU's in this country (including all of your examples) are utilized either on low-volume light rail or commuter rail lines, either to supplement existing, higher capacity service (eg. NJT River Line, San Diego Sprinter)or as a "poor mans" option to introduce transit in urban areas with none (eg. Austin).

That said, the Southern MD LR line is a decent candidate for DMU vehicles (depending on ridership estimates), but would still be considered light rail. DMU's aren't practical for high-volume light rail lines though (eg. the Purple Line) because the motive power equipment eats up a lot of passenger space compared to electrically-powered vehicles.

MARC, along with other commuter railroads in the Northeast such as Metro-North and NJ Transit, used to run Budd DMU's on certain lines but that option clearly isn't practical anymore. In addition, the current European-style DMU's being sold here cannot be mixed with freight (without a special FRA exemption), which would never happen on the CSX lines in MD/DC.

The vast majority of the major metropolitan areas in the Northern and Western parts of the country don't use DMU vehicles precisely because of these and other limitations.

by King Terrapin on Apr 9, 2013 3:50 pm • linkreport

There are so many corridors that would benefit from such services. Definitely the Brunswick Line and Camden Line, as their service is predominately for DC-based commuters with little reverse service. I think it would also be a good alternative to connect Annapolis, Fairfax, Southern Maryland, extant parts of Loudoun County, Columbia, and maybe even a quicker, more direct connection to Frederick. I also think it would be a big hit in Baltimore and Norfolk.

Is there any reason DMU would be better than EMU other than capital overhead for infrastructure?

by Dave Murphy on Apr 9, 2013 4:09 pm • linkreport

@king terrapin
True, DMU should lead to EMU if capacity becomes a problem. But there is talk at Stadler that the upcoming Tier 1 FRA crash rules change would allow off-the-shelf DMUs to run with freight, which would open up the CSX lines.

by David Edmondson on Apr 9, 2013 4:09 pm • linkreport

I would imagine that having DMU would be a maintenance nightmare. Each unit has to have engine work done and while it is being done it cannot be used as a simple rail car without decreasing the speed. Having the dedicated engines will allow you to swap out things much easier.

Speed is limited by the power compared to the weight, not the type of power being provided.

also the 79 mile per hour speed limit is due to signaling in the US not innate speed problems.

by Richard Bourne on Apr 9, 2013 4:11 pm • linkreport

DMUs accelerate and decelerate faster which means they are more efficient than locomotive-hauled trains for servicing closely-spaced stops. E.g. on the Portland line there are 5 stations along 15 miles, you would never want to run a locomotive-hauled train along that.

I would imagine that having DMU would be a maintenance nightmare. Each unit has to have engine work done and while it is being done it cannot be used as a simple rail car without decreasing the speed. Having the dedicated engines will allow you to swap out things much easier.

I'm not sure how this is different from any other transit vehicle - while you are working on it you can't use it. You just take it out and use a spare in your trainset if you want.

by MLD on Apr 9, 2013 5:04 pm • linkreport

I would imagine that having DMU would be a maintenance nightmare.

Actually, we've already been down this road before. They used to be exceedingly common in the US. A combination of the major railroads leaving the people moving business (they were the primary operators) and equipment age put an end to it. I don't think they'd have operated them, in one form or another, for a good sixty years if they'd been maintenance problems. Railroads are ruthless when it comes to sidelining equipment that's got a bad reputation.

by Another Nick on Apr 9, 2013 5:21 pm • linkreport

DMUs seem to work best in areas were there are lots of old or under used freight lines in a relatively suburban setting and with transit entities that don't want to spend a lot to bring rail transit. The NJT Riverline is a good example.

I'm not saying DMUs can't work in the DC area. The Virginia and Maryland exurbs would work great there. However, I'm not sure it would work in congested areas. It seems that most transportation organizations don't see DMUs as a efficient mode for intermediate distances and rather go with light rail.

@MLD
I think Richard's point was that EMUs, say most of SEPTA's regional rail fleet, have rolling stock that serve a duel purpose of propulsion and passenger accommodation. You can work on one two-car pair without loosing an entire trainset.

With most DMUs, you have trainsets that can't be run separately. This will probably be a problem for the new 7000 series, which I believe have 4-car trainsets and are not compatible with non 7000 series trains.

by Randall M. on Apr 9, 2013 5:59 pm • linkreport

DMUs seem to work best in areas were there are lots of old or under used freight lines in a relatively suburban setting and with transit entities that don't want to spend a lot to bring rail transit. The NJT Riverline is a good example.

The other advantage is that DMUs allow you to run a transit-like service. The Riverline is a good case, where instead of running regular commuter rail (full trains) infrequently, they run shorter DMUs much more frequently. The Riverline runs every 15 minutes at the peak and every 30 off-peak.

That's all on a 34 mile long line, with only 20 vehicles!

Given the rolling stock requirements to operate traditional AM-in, PM-out commuter rail, and you'd need a lot more cars than that and find a place to lay them over during the mid-day.

by Alex B. on Apr 9, 2013 6:33 pm • linkreport

MARC's amazing Budd DMU's

by King Terrapin on Apr 9, 2013 6:36 pm • linkreport

With the DMU's you could always go the route London took when they first created the underground gaps in the tunnels to accommodate the steam engines the same principal could be used for diesel trains so it is not impossible.

BTW the Metro does not have frequent stops on all portions specifically the Blue Line in VA, and Orange line east of the Anacostia and the Red Line in DC north of Union Station

by kk on Apr 9, 2013 10:54 pm • linkreport

"The other advantage is that DMUs allow you to run a transit-like service. The Riverline is a good case, where instead of running regular commuter rail (full trains) infrequently, they run shorter DMUs much more frequently. The Riverline runs every 15 minutes at the peak and every 30 off-peak."

The Riverline was built on the cheap, and has already reached capacity. It probably should have been full-fledged (NY-style) commuter rail to begin with, as it needs longer trains (and more equipment) and longer platforms.

The problem is that DC has a non-functioning commuter rail system, in that MARC and VRE are pretty much rush hour only services. Stamford and White Plains, for example, have better than 30-minute frequencies for most of the day, seven days a week, using traditional EMUs. In fact, Metro-North used to use Budd DMUs on their quieter branch lines, but had to go to locomotive-hauled trains after Budd left the business and no builder of FRA mandated equipment was left.

DMUs are still not the fast accelerators EMUs are, and are best placed in areas with expectations for low service and low capacity, where locomotive-hauled trains or electrification are too expensive.

by Walter on Apr 10, 2013 1:17 am • linkreport

The old Baltimore and Potomac lines from Bowie to Waldorf, Popes Creek, and Chalk Point would be obvious places to try this, since the coal trains are few and very regular.

The passenger demand appears to be very light in that corridor as people living there usually want to go to DC rather than Baltimore. But this would allow a southern extension of any line from Branch Avenue to Waldorf.

Moreover, if the Orange Line is extended to Bowie before the Southern Maryland light rail line gets underway, then using the existing rail lines with DMUs to connect Waldorf to the Orange Line may start to become a preferred option.

by JimT on Apr 10, 2013 8:36 am • linkreport

An item on DMUs I'm not familiar with: if new track construction is necessary, how robust of a track does one need to run DMUs, compared to LRT?

by Froggie on Apr 10, 2013 9:49 am • linkreport

DMU's would be a great option.Washington-Baltimore to Gettysburg-Hanover or DC to Hagerstown Cumberland Parkersburg what about DC to Harper's Ferry csx/ns to Front Royal on to Roanoke. Norfolk to Raleigh - Charlotte.Atlanta -Chattanooga-Nashville or Knoxville. A good way to start service fast and cheaply rather than diesel we should look to natural gas...nothing new here Europe uses this technology and has for years...buy or least off the shelf...

by Tom Minetree on Apr 10, 2013 11:10 am • linkreport

Actually the concept is for something like the German S-bahn or the Paris RER - a regular frequency regional service. Whether it is electric or diesel is not the point - though these services are in most cases electric because of faster acceleration and no fumes in tunnels. These things work best when lines do NOT terminate in the center, but rather run through. For example, a through service from Baltimore to Richmond via Union Station. That would require station modifications, but S-bahn and RER use high-level platforms at practically all stations - for speed of loading and convenience of pax.

by Dan Gamber on Apr 10, 2013 12:06 pm • linkreport

The Budd cars formerly used in Baltimore (and still used in Dallas) are essentially just commuter rail with self-propelled cars, just as SEPTA's and NJ Transit's EMUs closely resemble Marc's electric locomotive-drawn trains. The new concept could more accurately be called DLRT (Diesel Light Rail Transit), and shows promise in markets where the density doesn't justify the capital investment for electrification (yet), and the slower acceleration and fumes are not a problem. But another problem with the high-frequncy small-train model is the labor cost. The primary driver of transit cost is the driver. Also, no reason the cars could not be maintained at night, as most transit vehicles are.

by Greg Hinchliffe on Apr 10, 2013 7:53 pm • linkreport

@Walter

I wouldn't consider MARC & VRE "non-functioning." First of all you can't directly compare the commuter rail services in New York to since the 22m resident Metro Area is far larger and more dense than DC's (or anywhere else in this country). Secondly, the reason neither service has operated on the weekend (although MARC is trying to change that) is because, unlike every other major metropolitan area the vast majority of commuters work for the federal government and don't work on weekends/holidays.

Also, on the Penn Line MARC operates at least hourly service all day long. Honestly, the frequencies on the Penn Line (at least between Balt and DC) are perfectly fine, except for maybe the addition of a train or two to extend service to midnight and later. The critical improvement here for this line is to add weekend service, which Amtrak doesn't want to do. Similarly CSX won't let MARC run more midday trains (or rush hour trains for that matter) on the Camden and Brunswick Lines or bidirectional service on the Brunswick Line, which is severely hindering the growth of both.

@ Greg Hinchliffe

"The Budd cars formerly used in Baltimore (and still used in Dallas) are essentially just commuter rail with self-propelled cars, just as SEPTA's and NJ Transit's EMUs closely resemble Marc's electric locomotive-drawn trains. The new concept could more accurately be called DLRT (Diesel Light Rail Transit), and shows promise in markets where the density doesn't justify the capital investment for electrification (yet), and the slower acceleration and fumes are not a problem."

ditto. Well said.

by King Terrapin on Apr 11, 2013 12:57 pm • linkreport

Honestly, the frequencies on the Penn Line (at least between Balt and DC) are perfectly fine,

It's too bad that we set the bar so low.

And this kind of thinking is part of the problem:

Secondly, the reason neither service has operated on the weekend (although MARC is trying to change that) is because, unlike every other major metropolitan area the vast majority of commuters work for the federal government and don't work on weekends/holidays.

This is why we should frame MARC/VRE as regional rail rapid transit, not 'commuter rail,' because then people get the mindset that it is only useful for traditional commutes - and a subset of those at that.

by Alex B. on Apr 11, 2013 1:02 pm • linkreport

because, unlike every other major metropolitan area the vast majority of commuters work for the federal government and don't work on weekends/holidays.

Is this really even that true? It's at least self fulfilling, in Burke most people who take the VRE probably work a straight 9-5 tip but that's because that's the only service that exists. If the blue line went to Burke instead of Springfield you'd probably see all the people who need metro to work on weekends living in Burke instead.

by drumz on Apr 11, 2013 1:09 pm • linkreport

The NJT RiverLine is a Light Rail DMU: http://en.wikipedia.org/wiki/River_Line_(New_Jersey_Transit)

by NS on Apr 11, 2013 3:36 pm • linkreport

@ Alex B.

You can't change MARC/VRE into "rapid transit" unless you want to rip up the tracks, add a new Metro line and call it "MARC" or "VRE." By definition MARC/VRE is traditional commuter/regional rail. Rapid transit doesn't work over long distances. For instance it doesn't make any sense to build a Metro line to Martinsburg, WV or Perryville, MD (the terminuses of the Brunswick and Penn lines).

As Walter mentioned you can have higher frequency commuter rail, as is the case in the New York systems, but you need the densities and ridership to support it. Right now, MARC's priorities for the Penn Line should be to expand BWI airport station to 3 platforms and to add weekend service (possibly by having MD's Congressional delegation putting some political pressure on Amtrak).

by King Terrapin on Apr 11, 2013 6:31 pm • linkreport

You can't change MARC/VRE into "rapid transit" unless you want to rip up the tracks, add a new Metro line and call it "MARC" or "VRE." By definition MARC/VRE is traditional commuter/regional rail.

What? Yes, we absoltely can. I'm not saying it won't require investment, but the first thing is to break folks like yourself out of that box.

There is absoltely no reason your definition needs to be that way. It's a completely artificial distinction.

Rapid transit doesn't work over long distances. For instance it doesn't make any sense to build a Metro line to Martinsburg, WV or Perryville, MD (the terminuses of the Brunswick and Penn lines).

First, rapid transit can indeed work well over long distances. Metro covers some pretty long distances, after all.

Did I suggest turning the entirety of the MARC system into rapid transit? No, of course not. But those far extensions of the network account for a small portion of the total ridership. The core of a merged S-Bahn, RER-style network would extend to, say, Manassas and Woodbridge and Frederick and Baltimore, with your 'traditional' commuter service extending beyond as needed.

As Walter mentioned you can have higher frequency commuter rail, as is the case in the New York systems, but you need the densities and ridership to support it.

And lots of places already have that kind of density. Others have land uses ripe for redevelopment and increased intensity. No need to do the chicken-egg thing, make the service improvements now.

The rapid transit approach avoids the need for large, expensive storage at Union Station since you would make use of through-running trains (allowing you to store them at the ends where land is cheaper).

by Alex B. on Apr 11, 2013 6:49 pm • linkreport

Beware of DMU. It is very costly. Light Rail costs an average of $ 240 per car hour, but DMU is from $ 550 per hour in Oceanside and Camden to $ 1,200 in Portland and Austin. That is unaffordable. It is also slower than electric making
more hourly costs. It can not serve subway stations as it would asphixiate pass-engers. It can not serve VRE as CSXT will not allow off-peak service and peak service is less costly with big cars and locomotives. MARC's Penn Line can well use electric MUs faster and cheaper than dMU but MARC says locomotives are less costly with four-car trains which they think they need. E d T e n n y s o n

by Ed Tennyson on Apr 12, 2013 12:00 am • linkreport

DMU's can be very helpful in establishing or extending rail service quickly. US Railcar makes an FRA certified DMU that works without waivers on existing freight track. New DMUs use more efficient, less polluting EPA tier 4 engines. Compared a locomotive hauled train set, they are very quiet and save fuel. We are now working on a CNG version. Great Blog!

by Ted Schaefer on Apr 12, 2013 10:24 am • linkreport

Yeah, Austin is a misleading example - the train we got has a very wide turning radius and can't, as a matter of fact, operate in the street like light rail would. It's running on a freight rail corridor - no new in-street track was added, because it would not have been able to navigate any of our downtown corners (even a long LRT train could have done so).

Likewise, take a google maps tour of Camden to look at their similar "sell to people like it's light rail but stick them with a diesel monstrosity" service and note how many blocks they cut across diagonally to "operate in the street like light rail would". Compare/contrast to Houston.

by M1EK on Apr 17, 2013 5:13 pm • linkreport

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