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May 05, 2023

Why DC and Baltimore are different colors from space

PhotographyNews/AnalysisBy DW Rowlands (Contributor) March 2, 2022 10 This

PhotographyNews/AnalysisBy DW Rowlands (Contributor) March 2, 2022 10

This article was first published on September 21, 2020. After news in January that DC has selected a contractor to replace 75,000 streetlights with energy efficient LEDs — as well as controversy around the proposed P3 — we wanted to share this piece with you again.

On July 15, the crew of the International Space Station posted a nighttime photo of our region from space on Twitter, likening Washington, DC and Baltimore to "two galaxies swirling near each other." This photo gives us the opportunity to make a number of observations about the region.

DC and Baltimore City are different colors at night

The first thing that stands out when one looks at the ISS crew's photo nighttime lighting in our region is that the Washington region looks orange while the Baltimore region looks white. If they actually were galaxies, this would imply that Washington was significantly older and made up of mature stars fusing helium instead of hydrogen, or else that it was significantly further away and retreating at a high velocity. What is actually going on, however, is something more mundane: a difference in the District's and Baltimore City's street lighting choices.

Baltimore recently completed a program, called Bmore Bright, to replace all of the city's street lights with modern LED street lights, which are more energy efficient and have longer lifespans than the various types of high-energy discharge lamps that have historically been used for street lighting.

While the District is currently in the planning phases of a similar project, only 5% of the street lights in DC are currently LEDs, while 86% are high-pressure sodium high-energy discharge lamps. While LED street lights are designed to replicate the color distribution of sunlight, and so appear white, high-pressure sodium lamps have a distinctly orange glow, giving the District its orange appearance in the photo.

The District's consistent use of high-pressure sodium lamps also helps the DC-Maryland border stand out fairly clearly in the map: the close-in Maryland suburbs are lit with a variety of types of street lights, unlike the District's consistent orange glow. Likewise, in Baltimore, the Seagirt Marine Terminal and Mid-Atlantic Terminal port facilities stand out because their orange sodium-lamp illumination contrasts sharply with the city's white LED streetlights.

The Sparrows Point warehouse facilities facilities, on the bay side of the Baltimore Beltway Francis Scott Key Bridge, on the other hand, glow blue-white, suggesting that they are illuminated with LED, metal-halide, or mercury-vapor lamps.

A view of Chicago from space, taken 5 August 2016. by NASA / International Space Station Expedition 47 Crew licensed under Creative Commons.

This visualization of borders from street light colors is possible elsewhere in the county as well. In the photo above, the borders of the city of Chicago are clearly visible because Chicago also used orange sodium-vapor street lights when the photo was taken in 2016, while its suburbs did not.

Baltimore and Washington aren't "twin cities" the way Dallas-Ft. Worth are

In the Twitter thread where the photo was originally posted, several people commented on Washington and Baltimore being "twin cities" or made comparisons to Dallas-Fort Worth. However, while the Washington and Baltimore suburbs do somewhat blend together with lines of continuous development in the US-1/I-95 and— to a lesser degree— Baltimore-Washington Parkway corridors, they are still visually very distinct in the view from space.

In comparison, Dallas and Fort Worth — with downtown cores 30 miles apart, not much less than the 35 miles that separate downtown Baltimore from downtown DC — really do blur together into one continuous area of development when viewed from space, as in the photo below.

While downtown Dallas is identifiable as the bright core in the lower right of the image and downtown Fort Worth is visible as a smaller bright core in the lower left, with the commercial core of Arlington, Texas in between them, it is hard to identify a clear boundary between what is Dallas and what is Fort Worth, and the only dark areas are several lakes and the parkland along the Trinity River, which connects the two cities.

A view of Dallas-Fort Worth from space, taken 3 January 2020. by NASA / International Space Station Expedition 61 Crew licensed under Creative Commons.

To help give a clearer view of the relative scales of our region and several of the US's largest metropolitan regions, I created an image showing the views of Baltimore-Washington, Dallas-Fort Worth, Los Angeles, and New York from space, all at the same scale and with all images rotated with north at the top.

In this image, we can see that the Dallas-Fort Worth region, which has roughly the same population as the Baltimore-Washington region, is also similar in size to our region, but with much more consistent density across a continuous area, while the density in our region is concentrated in the cores of the District and Baltimore, along with a few linear suburban corridors.

Clockwise from upper left, Baltimore-Washington, Dallas-Fort Worth, New York, and Los Angeles from space at the same scale. by the author.

New York, on the other hand, can fit its densest areas — New York City, Newark, Hudson County in New Jersey, and southern Westchester and eastern Nassau Counties in New York — in the space between the District and Baltimore, even though those areas combined have a significantly larger population than our region.

Meanwhile, the core regions of the Los Angeles metro area — the Los Angeles basin proper, the San Gabriel and San Fernando Valleys, and the northern portion of Orange County — with a smaller population than the core portion of the New York metro area, sprawl out over a significantly larger region.

The structure of the Baltimore-Washington region from space

This photo of our region gives a good view of the general structure of development — especially commercial development, which is generally more brightly-lit and where street lighting is less obscured by trees — in our region. While a number of well-lit suburban corridors extend from Baltimore, none are as prominent as the Rockville Pike/I-270 corridor that extends almost directly from the District to the top of the photo.

A view of the Washington (left) and Baltimore (right) regions from space, taken 15 September 2020. by NASA / International Space Station Expedition 63 Crew licensed under Creative Commons.

Other notably long corridors that extend outward from Washington include the Branch Avenue corridor to Waldorf visible in the lower left of the image and the Richmond Highway and the Beltway corridors in Fairfax County at the center left.

The Dulles Toll Road, which extends from the bright cluster of Tysons through Reston to an orange blotch that appears to be Dulles International Airport at the upper-left of the image is somewhat less identifiable, in part because the low-density development in the Difficult Run watershed produces a gap in illumination between Tysons and Reston.

The only traditional urban core besides Baltimore and Washington visible in the image is Annapolis, in the lower center: Frederick, which is at the northern end of the I-270 corridor, is just beyond the top edge of the image near the center. While the I-270 corridor from Washington to Frederick is very visible and the Governor Ritchie Highway corridor between Baltimore and Annapolis can be made out, the I-70/US Route 40 corridor between Baltimore and Frederick, like the US Route 50 corridor between Washington and Annapolis, goes through largely undeveloped areas and is not visible.

Interestingly, several different visible corridors link Baltimore and Washington. To the south, the Robert Crain Highway corridor through Gambrills and Crofton links the southern suburbs of Baltimore to Bowie and Upper Marlboro in Washington's eastern surburbs. North of this is a very dark patch, consisting of the research farmland of the USDA Beltsville Agricultural Research Center and the forests of the Patuxent National Wildlife Refuge.

The main connection between Baltimore and Washington, however, consists of four closely-spaced and roughly parallel roads: from north to south Columbia Pike, I-95, US Route 1, and the Baltimore-Washington Parkway link the two metro areas. Of these four, only two are clearly visible in the image. Columbia Pike can be made out as a series of patches of light that appear to correspond to development at White Oak, Briggs-Chaney, and Burtonsville in Montgomery County and Scaggsville, Columbia, and Ellicott City in Howard County. The US Route 1 corridor is more consistently illuminated between Baltimore and Washington, with a downward-pointing corridor of light along Laurel-Fort Meade Road connecting it to the orange patch of sodium vapor lamps at Fort Meade.

A close-up view of Washington

A close-up view of the District and its inner suburbs shows DC as four concentric rings with different lighting patterns. At the very center, the National Mall and the undeveloped land around the White House form a dark corridor shaped like an inverted letter "T."

They are surrounded, however, by the brightest (and least orange) part of the District: the commercial core of Downtown, Capitol Hill, Foggy Bottom, and the Federal offices in Southwest near L’Enfant Plaza. This, in turn, is surrounded by a shell of less-brightly lit residential areas, roughly corresponding to the boundaries of the L’Enfant City but stretching almost to Silver Spring along 16th Street and Georgia Avenue.

Finally, the residential areas west of Rock Creek Park, the residential and industrial areas in Northeast, and the residential areas east of the Anacostia make up a fourth, even less-well-illuminated shell.

A close-up of DC and its inner suburbs from space. by Close-up of a portion of an image taken by NASA / International Space Station Expedition 63 Crew licensed under Creative Commons.

While the suburbs are less-consistently illuminated, a number of bright cores are recognizable within them, connected by well-lit arterial roads. In Montgomery County, Bethesda, White Flint, and the Montgomery Mall area all stand out north of the very-recognizable Wisconsin and Connecticut Avenue corridors in the District, while downtown Silver Spring is probably Montgomery County's single brightest cluster.

In Prince George's County, on the other hand, roughly continuous commercial development along the Beltway is fairly visible (in Montgomery County, much of the Beltway runs through parkland), but the Baltimore Avenue corridor through College Park, the University of Maryland, and Beltsville is quite visible, as is University Boulevard from the University of Maryland to Langley Park. Further south, development along US-50, Pennsylvania Avenue, and Branch Avenue stand out, as does National Harbor.

In Northern Virginia, Tysons (near the top left of the image, with Dunn Loring-Merrifield just south/left of it) is, unsurprisingly, the region's brightest suburban cluster. Development along Richmond Highway, starting with Crystal City and continuing past National Airport and Alexandria to the Richmond Highway corridor in Fairfax County is also quite prominent. The route of the Beltway, with Virginia Route 7 and Duke Street/Little River Turnpike within it is also quite recognizable, as is, to a lesser degree, development along I-395.

A close-up view of Baltimore

A close-up view of Baltimore at the same scale shows a smaller brightly-illuminated core and a spiderweb-like network of bright development along radial roads. The brightest of these, running toward the upper-right corner of the photo, is the Towson-Timonium-Lutherville corridor along York Road and I-83 in Baltimore County north of the city.

A close-up of Baltimore and its inner suburbs from space. by Close-up of a portion of an image taken by NASA / International Space Station Expedition 63 Crew licensed under Creative Commons.

A number of major corridors run northeast, toward the right side of the image, but the brightest area is the White Marsh area along the I-95/US-40 corridor. At the top of the photo, two bright corridors are visible: the brighter is the Reisterstown Road and I-795 corridor while the dimmer is the Liberty Road corridor. The lower-left of the photo, in the direction towards Washington, has less visible radial orientation, perhaps because radial roads in this area have to cross parkland and the valleys of Gwynn Falls and the Patapsco River. The bright orange blotch in this area appears to be development around Baltimore-Washington International Thurgood Marshall Airport.

What else do you see?

Do you see other interesting features of our region in these images? Please let us know in the comments!

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DW Rowlands is a human geographer and Prince George's County native, currently living in College Park. She is a senior research assistant at the Bass Center for Transformative Placemaking in the Metropolitan Policy Program at the Brookings Institution. More of her writing on transportation-related and other topics can be found on her website.