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Demographics


A city can be diverse but its neighborhoods may still not be. (And DC scores poorly on both measures.)

How do you measure a city's diversity? If a city has a lot of different racial and ethnic groups in their own segregated sections, is that diverse?

A blog called priceonomics recently ranked major American cities on diversity by looking at the percentage of major racial and ethnic groups within the city's limits. The District of Columbia came in 21st, slightly less diverse than Oklahoma City.


Photo by Eric Hews, erichews.com posted with permission.

However, while this analysis is useful, it it doesn't reveal whether the neighborhoods in each city are themselves diverse, or whether the city boundary just encompasses some all-black areas, other all-white areas, and so on.

If we modify this methodology to measure the average diversity of a city's neighborhoods, rather than of the city as a whole, we are able to quantify how integrated these place are. On this new measure, the District performs even worse.

A neighborhood-level calculation changes the results

Consider Chicago. With roughly equal-sized black, white, and Latino populations, the Windy City ranks as the fifth most diverse city in the country on the priceonomics scale. However, if we instead use priceonomics' same methodology (it took the percentage of black, white, Asian, Latino, and other people in the city, then used a Herfindahl-Hirschman Index to combine those numbers into a single score) for each of Chicago's individual census tracts, then take the weighted average, Chicago suddenly drops to 38th out of 45.

Chicago, as a whole, is diverse, but its neighborhoods are not. The average Chicago census tract is less diverse than a typical tract in Portland or Colorado Springs, both relatively homogeneous cities that scored near the bottom in the original citywide index. Both are close to 70% white, but the non-white population isn't all clumped in a small non-white area.


Chicago's diverse population is largely segregated. Sacramento is diverse, and so are its neighborhoods.

Here are the scores for all of the cities in the analysis. You can click on a column in this table to sort it. Click on the name of any city in this table to see a map of that city's Census tracts and their diversity levels.

NameNew rankDiversity index
(neighborhood)
Original rankDiversity index (citywide)Rank change
Sacramento10.32477820.2493451
Oakland20.36768210.234220-1
Long Beach30.40482440.2853671
Fresno40.419840150.33261611
San Jose50.41991260.2959631
San Francisco60.42005080.3118102
Las Vegas70.439887170.33810610
San Diego80.46835190.3127091
Fort Worth90.478435130.3246714
Albuquerque100.482462270.39906417
Charlotte110.495846160.3369055
Boston120.49635170.310615-5
Austin130.500739190.3712116
Oklahoma City140.502493200.3743756
Virginia Beach150.510308330.45543618
Raleigh160.512390220.3810926
Houston170.518201100.313724-7
Tucson180.518248260.3990558
New York190.52082730.260531-16
Jacksonville200.524788250.3985755
Los Angeles210.526386180.339228-3
Dallas220.531520120.321215-10
Denver230.536938240.3874161
Nashville240.538537290.4088575
Seattle250.545698370.47687612
Mesa260.553278380.49269412
Phoenix270.556085230.384986-4
Indianapolis280.565431310.4226303
Columbus290.565687320.4305333
Colorado Springs300.565902410.52823311
Portland310.569062430.53941712
San Antonio320.574919350.4746363
Kansas City330.579408280.399368-5
Milwaukee340.589951110.320661-23
Philadelphia350.599411140.331147-21
Washington360.611801210.378045-15
Omaha370.613333390.5010412
Chicago380.63299350.290745-33
Louisville390.656964400.5181451
Memphis400.670075340.474338-6
Atlanta410.670933300.416675-11
Baltimore420.681552360.475331-6
El Paso430.706141440.6633451
Miami440.732796420.536259-2
Detroit450.795764450.6741850
Note: Priceonomics used the 2013 1-year American Community Survey estimates for their analysis. This analysis uses the 5-year estimates, because it is available at both the Place and Census Tract levels. As a result, the citywide index scores may vary slightly from the data presented by Priceonomics.

California cities dominate the adjusted rankings, accounting for the top six spots: Sacramento, Oakland, Long Beach, Fresno, San Jose, and San Francisco. Virginia Beach moved up 18 slots, representing the largest jump of any one city.

DC, on the other hand, drops into the bottom quartile, neck and neck with Omaha. Like Chicago (well, not quite as bad as Chicago), the District's citywide diversity doesn't extend to diversity within most of its neighborhoods.


The diversity of each census tract in DC.

How citywide diversity relates to neighborhood diversity

There is a correlation between diversity in a city and diversity within its neighborhoods, although places like Chicago and DC remind us that it is not necessarily as strong relationship. Here's a scatter plot comparing the citywide and neighborhood average diversity indices for each of the 45 cities:


Diversity within neighborhoods compared to overall city diversity, with the most integrated and most segregated cities labeled.

Cities above the trend line have less diverse census tracts than the city's overall diversity would suggest. These are therefore relatively segregated. Chicago and DC fall into this category.

Miami is among the least diverse cities on the entire list (remember that according to this methodology, "diversity" only considers 5 distinct groups, lumping together, for example, everyone who identifies as Hispanic/Latino), but on a neighborhood level it's even more segregated still.

Cities below the trend line have neighborhoods that are more diverse than comparable cities at their level of citywide diversity. This group includes Sacramento, which is both diverse and integrated, as well as Portland, which is not diverse, but relatively well-integrated.

Diversity and integration are both important, and the District has a long way to go on both measures. What do you notice?

Cross-posted at R.U. Seriousing Me?

Transit


How to tell the difference between streetcars and light rail

There is much confusion over what separates streetcars from light rail. That's because there's no single easy way to tell, and many systems are hybrids. To tell the difference, one has to simultaneously look at the tracks, train vehicles, and stations.


San Francisco's Muni Metro runs both in a dedicated subway and on the street in mixed traffic.
Is it a streetcar or light rail system? Photos by Matt Johnson and SFbay on Flickr.

It's hard to tell the difference because streetcars and light rail are really the same technology, but with different operating characteristics that serve different types of trips.

The difference, in a nutshell

Theoretically light rail is a streetcar that, like a subway or el, goes faster in order to serve trips over a longer distance. But what does that mean in practice?

There are several features of tracks, vehicles, and stations that both streetcars and light rail sometimes have, but which are generally more common on light rail. Thus, although there's no single separating test that can tell the two apart with 100% accuracy, it's usually possible to tell the difference by looking at several factors simultaneously.


Image by the author.

Let's look at each of those factors, one by one.

Lanes and tracks

It's a common misconception that streetcars always run in mixed traffic with cars, while light rail has its own dedicated track space. That's often true, and it's such a convenient and easy-to-understand definition that I've been guilty of using it myself. But it's wrong.

There are too many exceptions to that rule to rely on it completely. Sometimes (though rarely) light rail lines run in mixed-traffic, and there are plenty of streetcars with their own right-of-way. Some streetcars even have subways.

Compare Sacramento's mixed-traffic light rail with Philadelphia's streetcar subway, for instance:


Left: Sacramento light rail in mixed traffic. Photo by Flastic on Wikipedia.
Right: Philadelphia streetcar in a subway. Photo by John Smatlak on Flickr.

In fact, practically every mixed-traffic streetcar has at least a short section of dedicated track. That's true in Atlanta, Seattle, Tucson, even DC. Those streetcar lines don't suddenly become "light rail" for one block just because they have a dedicated lane somewhere. It's just not that simple.

And some streetcars have long stretches with dedicated lanes. Toronto's massive streetcar network has several dedicated transitways, and DC is planning one on K Street.


Left: K Street transitway. Image from DC Streetcar.
Right: Toronto's Saint Clair transitway. Photo by Sean Marshall on Flickr.

There are too many streetcars with dedicated lanes for that to be a reliable indicator on its own. Too many lines that mix dedicated and non-dedicated sections. Certainly it's an important data point; certainly it's one factor that can help tell the difference. But it's not enough.

An even simpler definition might be to call anything with tracks in the street a streetcar, and anything with tracks elsewhere light rail.

But that's not reliable either, as Portland and New Orleans illustrate:


Left: Portland light rail. Photo by BeyondDC.
Right: New Orleans streetcar. Photo by karmacamilleeon on Flickr.

Salt Lake City muddies the water still further. Its "light rail" mostly runs in the street, while its "streetcar" runs in an old freight train right of way, almost completely off-street.


Left: Salt Lake City light rail. Photo by VXLA on Flickr.
Right: Salt Lake City streetcar. Photo by Paul Kimo McGregor on Flickr.

Vehicles and trains

If tracks on their own aren't enough to tell the difference, what about vehicles?

It's tempting to think of streetcars as "lighter" light rail, which implies smaller vehicles. Sometimes that's true; a single DC streetcar is 66 feet long, compared to a single Norfolk light rail car, which is over 90 feet long.

But not all streetcars are short. Toronto's newest streetcars are 99 feet long.


Toronto streetcar. Photo by Canadian Pacific on Flickr.

In fact, many light rail and streetcar lines use the exact same vehicles. For example, Tacoma calls its Link line light rail, and uses the same train model as streetcars in Portland, DC, and Seattle, while Atlanta's streetcar uses the same train model as light rail in San Diego, Norfolk, and Charlotte. And Salt Lake City uses the same train model for both its streetcar and light rail services.


Left: Tacoma light rail. Photo by Marcel Marchon on Flickr.
Right: Portland streetcar. Photo by Matt Johnson on Flickr.


Left: San Diego light rail. Photo by BeyondDC.
Right: Atlanta streetcar. Photo by Matt Johnson on Flickr.

And although streetcars often run as single railcars while light rail often runs with trains made up of multiple railcars, there are exceptions to that too.

San Francisco's Muni Metro and Boston's Green Line definitely blur the line between streetcar & light rail, perhaps more than any other systems in North America. Some might hesitate to call them streetcars. But they both run trains in mixed-traffic with cars, and some of those trains have multiple railcars.

Meanwhile, many light rail systems frequently run single-car trains, especially during off-peak hours.


Left: Norfolk light rail with a single car. Photo by BeyondDC.
Right: San Francisco streetcar with two cars. Photo by Stephen Rees on Flickr.

Stations offer some help, but no guarantee

Light rail typically has bigger stations, while streetcars typically have smaller ones. A big station can sometimes be a good clue that you're likely dealing with light rail.

For example, look at Charlotte and Portland:


Left: Charlotte light rail. Photo by BeyondDC.
Right: Portland streetcar. Photo by BeyondDC.

But that's only a general guideline, not a hard rule. Just like tracks and vehicles, there are many exceptions. Light rail often has small stops, and streetcar stations can sometimes get pretty big (especially when they're in a subway).

This light rail stop in Norfolk is smaller than this streetcar stop in Philadelphia, for example:


Left: Norfolk light rail. Photo by BeyondDC.
Right: Philadelphia streetcar. Photo by BeyondDC.

Stop spacing and route length

Probably the most reliable way to tell streetcars apart from light rail is to look at where the stations are located. Light rail lines typically have stops further apart from each other, on lines covering a longer distance.

This chart explains the difference:


Image from Jarrett Walker.

This is the definition transit expert Jarrett Walker favors, and if you have to pick just one or two factors to consider, stop spacing and route length are the best.

But even this is no sure way to categorize all lines as either streetcars or light rail. It might be easy to tell the difference between something with stops one block apart (theoretically streetcar) versus stops two miles apart (theoretically light rail), but what if the stops are 1/4 mile apart? Or what if the gaps aren't consistent? There's no clear place to draw the line.

Furthermore, Walker's graphic itself illustrates exceptions to the rule. The top line shows a light rail route with stops close together downtown, the third line shows a streetcar with some sections that have far-apart stations, and the fourth line shows a very long streetcar.

There are certainly plenty of real-life examples of those exceptions. Before Arlington, VA cancelled its Columbia Pike streetcar, DC and Arlington were considering linking their streetcars with a bridge over the Potomac River. Had that happened, there might have been a mile-and-a-half between stops.

Certainly station spacing and route length provide a convenient general rule, but only that. There's no hard boundary where everything to one side is streetcar, and everything to the other is light rail.

To really know the difference, look at everything

There are seven factors that light rail usually has, but that streetcars only sometimes share: Dedicated lanes, off-street tracks, bigger vehicles, multi-car trains, longer routes, bigger stations, and long distances between stations.

No single one of them provides a foolproof litmus test, because sometimes streetcars have each of them, and sometimes light rail doesn't. But if you look at all seven together and determine which direction the majority of a line's characteristics point, over the majority of its route, then you can usually sort most lines into one category or the other.

For example, DC's H Street line fits neatly into the streetcar category, because it runs in the street almost totally in mixed traffic, with small vehicles on single-car trains, along a short route that has frequent, small stations. Even if DDOT builds the K Street transitway and a dedicated-lane streetcar on Georgia Avenue, the majority of the seven factors will still point to streetcar.

On the other end of the spectrum, Seattle's Central route is squarely light rail. It has a dedicated right-of-way that's often off-street, uses large 95 foot-long vehicles that are usually coupled into multi-car trains, along a long route with infrequent stations.


Left: Seattle light rail. Photo by Atomic Taco on Flickr.
Right: DC streetcar. Photo by BeyondDC.

But even then not every system is crystal clear. San Francisco's Muni Metro, Philadelphia and Boston's Green Lines, and Pittsburgh's T, for example, all have some segments that look like classic streetcars, but also some segments that look like classic light rail. These networks defy any characterization, except as hybrids.

It's a feature, not a bug

The fact that it's hard to tell the difference is precisely why so many cities are building light rail / streetcar lines. The technology is flexible to whatever service characteristics a city might need.

You can use it to build a regional subway like Seattle, or you can use it for a short neighborhood circulator like DC's H Street, or anything in-between. And perhaps even more importantly, you can use it to mix and match multiple characteristics on the same line, without forcing riders to transfer.

That's why many of the most successful light rail / streetcar systems are the hardest ones to categorize as either / or. They match the infrastructure investment to the needs of the corridor, on a case-by-case basis, and thus have some sections that look like light rail, and others that look like streetcar.

That's not muddied. That's smart. That's matching the investment to the need, which is after all more important than a line's name.

Cross-posted at BeyondDC.

Bicycling


Photographic proof bikes and streetcars work together

Despite the fact that streetcar tracks can be hazards to cyclists, bikes and streetcars are great allies.


Amsterdam bikes and tram. All photos by Dan Malouff.

They both help produce more livable, walkable, less car-dependent streets. It's no coincidence that the same cities are often leaders in both categories. In the US, Portland has both the highest bike mode share and the largest modern streetcar network. In Europe, Amsterdam is even more impressive as both a streetcar city and a bike city.

With that in mind, here's a collection of photos from Amsterdam showing bikes and streetcars living together.

Of course, it doesn't just happen. It's easy for bikes and streetcars in Amsterdam to avoid one another, and to interact safely, because each one has clearly delineated, high-quality infrastructure.

Chalk it up as one more reason to build good bike lanes.

Cross-posted at BeyondDC.

Bicycling


94% of cyclists (in Portland) stop at red lights

A new study in Portland finds that 94% of bicyclists stop at red lights there.


Photo by Tejvan Pettinger on Flickr.

Is that just Portland? A 2012 analysis of DC cycletracks found 60% of riders stopped at red lights on the 15th Street cycletrack.

BikePortland quotes an expert who speculates that because so many people bike, it creates some peer pressure not to go through the lights.

Portland also has very short light cycles, and I wonder if that contributes. If you wait, you don't have to wait very long. It also means that while there might be more time when nobody can go while the lights change ("intersection-clearing time"), there may be less time when one side has a green but no vehicles are actually trying to go through—the time cyclists most often go through a red light.

The DC cycletrack analysis recommended retiming the lights as one way to cut down on red light running. If cyclists leave one intersection as the light turns green, but then the next one turns red just as they arrive, they're more likely not to wait than if it'll only be a short wait.

This follows a general principle: the more the road system (lanes, signal timing, etc.) is designed with cyclists in mind as well as drivers, the more people will obey the markings and signals.

As another example, the study says that 4% of the Portland riders started going into the intersection before the light turned green. People often do that to get some distance from cars which might be unexpectedly turning right, or whose drivers might be looking in another direction as they start into the intersection.

DC has recently added many leading pedestrian intervals, where the pedestrian walk sign goes on before cars have a green, and also changed the law to let cyclists start going when the walk sign changes. There hasn't been a study, but it seems very likely that far more cyclists are waiting until their legal chance to go now that the time they feel is safe, and the time when it's legal, match more closely.

As BikePortland notes, Chicago recently announced that red light compliance rose from 31-81% when it put in dedicated bike signals, but the Portland study found they made no difference. Could the shorter light phases and/or the greater numbers of cyclists in Portland mean that people felt safer in Chicago with the signals, but already felt safe enough in Portland without?

So when someone says "we shouldn't build more bike lanes until bicyclists follow the laws," besides the obvious retort that 36-77% of drivers speed yet we still build roads, building the bike lane to make legal riding safe is actually one of the best ways to get bicyclists to follow those laws.

Public Spaces


Can NoMa turn dank underpasses into lively public spaces?

Can the mostly-empty space beneath the railroad tracks approaching Union Station become active spaces that enhance the NoMa neighborhood? The NoMa Business Improvement District (BID) hopes so. Some other cities have been able to activate underpasses; can these show the way?


An idea for the L Street underpass from the NoMa BID public realm design plan.

The BID launched a design competition to find "an artist, team of artists, designer or architect" to "beautify, enliven and activate" the spaces under the tracks on Florida Avenue and K, L, and M Streets NE with a "sensory experience."

"We want to turn those spaces into places that people want to come visit because they are so attractive and cool," says Robin Eve-Jasper, president of NoMa BID.

Funding comes from the $50 million Mayor Gray recently authorized to help NoMa combat its dearth of parks. The DC Council still must approve the spending, but Eve-Jasper says that she expects this to happen by the end of May. Responses from design teams are due by May 9, with a plan to present proposals to the public in September and select a final design in October.

Underpasses get little activity today

Pedestrians currently use the underpasses as little more than empty zones to cross from one side of the tracks to the other.

M Street is the most active of the four, as it is the main access route to the NoMa-Gallaudet Metro station and the Metropolitan Branch Trail (MBT) for residents who live on the east side of the tracks. It also contains a Capital Bikeshare station on its northern sidewalk.

Neighborhood residents headed to NoMa's main activity center at the corner of M and First Street NE, where there is a Harris Teeter supermarket, other stores and offices, also use the M Street underpass.


M Street NE underpass looking west.

Cars dominate the Florida Ave and K Street underpasses, which dedicate six and four lanes to car traffic, respectively. Both streets have narrow sidewalks and see significantly less pedestrian traffic than M Street.


Florida Avenue underpass looking east.


K Street underpass looking west.

The L Street underpass is the least used of the four, according to my observations. It has wide sidewalks and only two lanes for cars—like M Street—but lacks easy access to the Metro or the MBT, and the activity center of its sibling a block north.


L Street underpass looking east. Photo by author.

Other cities have activated underpasses

Highway underpasses have become public space in a number of other cities. Many include basketball courts, bike trails, skate parks and play areas for children.

Underpass Park in Toronto, located under the western end of the Eastern Avenue overpass near the Don River, is a widely-cited example. A recent Architectural Record report found the park's basketball courts and skate park popular among area residents, but the children's area was less so.

The article also noted that an art installation called Mirage, which includes reflective panels that add light to the underpass, does provide some illumination but adds that more mirrors would have brightened the space.


Underpass Park, Toronto. Photo by Rick Harris on Flickr.

Other examples include Burnside Skatepark in Portland, Oregon and I-5 Colonnade Mountain Bike Park in Seattle, both of which are under overpasses.

The underpasses in NoMa lack the height and depth of many of these spaces. This makes it difficult to fit amenities like basketball courts or skate parks, though a linear children's play area could fit on either L or M Streets.

Chicago's Hyde Park neighborhood may offer some of the closest examples to the spaces in NoMa. A number of underpasses under a Metra rail line through the neighborhood sport murals by local artists and some even have corner shops built into their corners.


Underpass mural in Chicago's Hyde Park neighborhood. Photo by Marc Monaghan on Flickr.

Asked what NoMa BID envisions for the four spaces, Eve-Jasper says that she is leaving that up to the architects and designers to decide. What do you think would work best in the underpasses?

Parking


Politics, not good sense, drive Portland parking minimums

Opponents of DC's zoning update are touting news that Portland, Oregon is re-instituting parking minimums. They claim the Portland case proves eliminating minimums doesn't work. But it actually shows how sometimes leaders bow to political pressure and resident fears, even for a bad (popular) solution instead of a better (less understood) one.


SE Divison Street in Portland. Photo by Matt Kowal on Flickr.

Portland removed parking minimums in many neighborhoods with high-frequency bus lines in the 1980s. Recently, residents in the Richmond neighborhood pushed to reinstate some parking minimums after plans came to light for a new 81-unit building without off-street parking.

Many neighbors were frightened that the new building could make parking on street more difficult. It's an election year, and candidates wanted to cultivate votes from active residents in the area. They gave those residents what they wanted. Unfortunately for Portland, those residents skipped over a much better policy tool: on-street parking permits.

As Dick VanderHart explains in the Portland Mercury, the neighborhood has a vibrant nightlife which attracted new visitors to the area. Those visitors compete with residents for parking. Curbside parking is free at all times.

Residents can request residential permits to limit visitor parking and overnight parking. Last year, the city created a "mini" parking district program so individual neighborhoods can create new small parking districts, but so far, none have requested one.

Perhaps that's because it's not really hard to park there. In a Bureau of Planning and Sustainability (BPS) survey, most residents said that they usually park on the street 1-2 blocks from their homes and most spend little time looking for parking.

It isn't clear that a parking problem exists in Portland today. Plus, building more off-street parking will not do anything about visitors patronizing the new bars and cafes in the area. That's especially true as long as parking is free on every street in the area. No matter how much garage parking new buildings have, many people will find it more convenient and cheaper to park on the street until the city limits on-street parking or charges for it.

This closely parallels issues in DC. In many neighborhoods, it's becoming more difficult to park. We have parking minimums, but they clearly aren't preventing this. The solution is not to cling tenaciously to parking minimums, but to set up a better system that actually manages on-street spaces.

The Portland zoning code didn't fail. Instead, the residents didn't or couldn't use other parking management tools. We don't know yet if switching the code back will improve matters for unhappy residents—the vote just happened last week—but it's unlikely.

The new Portland policy require one space per 5 units for buildings with 30-40 units, one per 4 for buildings of 41-50 units, and one per 3 for buildings over 51 units. If the developer puts in bike parking and car sharing, they can relieve some of the requirement.

Perhaps because of the impending election, Portland's council may have acted hastily. The city was also working on other policies to deal with parking through basic transportation demand management measures, but that proposal was not finished in time for the council vote.

Opponents have been complaining most strongly about the DC proposal to exempt residential buildings of up to 10 units from parking requirements citywide. Portland still exempts buildings up to 3 times that size.

Plus, while many tout Portland as a transit mecca for its pioneering streetcars and other policies, the percentage of trips by transit here is triple that of Portland, which has no subway at all. TriMet has cut service in recent years, while WMATA has not. DC neighborhoods whose residents consider their transit fairly meager still have a lot of transit by the standards of many parts of Portland.

Portland's parking experience is not proof that parking minimums are necessary. Instead, it shows that politics can get in the way of good parking policy. Just because politicians in one city had a knee-jerk but nonsensical reaction to a certain neighborhood's complaints does not mean DC should do the same.

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.

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