Population Density, Race, and the Purple Line

d.w.rowlands [at] gmail.com

I recently came across a rather interesting map. It's a map of the US with population marked as one dot per person, randomly distributed inside each census block, and color-coded by race. This strikes me as a really interesting source of data, and one that I hope to do a number of blog posts on. I'm starting, though, by posting a map of the population density and racial distribution of residents along the Purple Line, a light rail line that Maryland is hopefully going to start building next winter to connect four branches of the Washington, DC Metro across the Maryland suburbs directly north of the District.

In the above map, I've marked the northern border of the District of Columbia with a thick grey line and the border between Montgomery County, MD (to the west) and Prince George's County, MD (to the east) with a thinner grey line. The red, green, and orange lines on the map are branches of the heavy-rail DC Metro. (The two red branches are connected as a single line off the bottom of the map.) The purple line, of course, is the Purple Line. The population color code is blue for white people, green for African-American people, orange for Hispanic people, and red for Asian-American people.

The west end of the Purple Line begins in Bethesda, a rather rich and increasingly dense inner-ring suburb. As we can see from the map, it's somewhat diverse, but largely white-and-Asian; it's also fairly young and hip. As the line runs east, it passes through a very rich, very white area called Chevy Chase which---perhaps not surprisingly---has been the one area along the line opposed to it, and has spent a huge amount of taxpayer money to sue to stop it. From there, the line continues through the dense and somewhat less rich and more diverse than Bethesda neighborhood of downtown Silver Spring.

From Silver Spring the line continues east towards Prince George's County, entering the poorer region of the DC area, which is largely delineated by the Beltway (which runs along the top and east sides of the map and 16th Street, which runs through the northern point of DC. After passing through an area of largely white single-family homes, it enters the "International Corridor" of Langley Park as it runs along University Boulevard to the University of Maryland campus. This area is one of the largest Salvadoran communities in the country and, as you can see from the map, is also one of the densest areas the Purple Line runs through, even though University Boulevard itself is a six-lane highway lined with strip malls with connected surface parking lots forming a de-facto service lane on each side. The Purple Line stop at New Hampshire Avenue on the county line is also at what is currently the most dangerous intersection for pedestrians in the state of Maryland, in part due to people running between bus stops at what is currently the busiest bus transfer station not at a Metro station in the DC area.

(As a side note, the density along New Hampshire Avenue running north of this station makes me wonder whether it would be worthwhile to run a branch of the purple line from here north along New Hampshire Avenue to White Oak: it would serve a number of dense residential areas as well as a significant shopping and employment district, including the new FDA center at the old Naval Ordinance Lab there.)

From Langley Park, the Purple Line passes through the less-dense single-family homes of Adelphi before passing apparently-largely-Asian grad student apartments as it enters the University of Maryland campus. Here we can see that the on-campus dormitory areas are fairly racially diverse, but the grad student apartments to the west and south of the campus are almost entirely Asian and the fraternity and sorority areas to the southwest of the campus and associated undergraduate apartments with a reputation for partying are almost entirely white.

The Purple line then passes the essentially uninhabited M-Square research park area before running through Riverdale and then down freeway-lite Veterans' Parkway, skipping the dense and largely African-American apartment complexes along the eastern end of Riverdale Road in New Carrollton. I'd always been a bit skeptical of this bit of the alignment, since the line skips densely-populated areas to go down a freeway. I suspect that the reason for it is that Riverdale Road is rather narrow in this area and they probably could not get away with giving the line dedicated lanes, which they can do on Veterans' Parkway. At the moment, the New Carrollton Metro Station terminal of the line is largely surrounded by surface parking, but there are significant plans for transit-oriented development in the area.