American taxpayers have spent trillions of dollars building freeways since the passage of the National Interstate and Defense Highways Act of 1956. This network of freeways has re-shaped American cities, and arguably impacted the economy and culture of the country. While some enthusiasts find interest in the highway system’s endless strips of asphalt, for most the only true drama within the system is contained in freeway interchanges, where one or more freeways intersect. Although designed by traffic engineers, interchanges can contain dramatic ramps and intriguing shapes from above. One artist even took inspiration from the world’s freeway interchanges to design a set of tiles featuring their shapes.
Of these highways, Washington, D.C.’s Capital Beltway is among the more famous, as a symbolic dividing line between the national capital and the rest of the country. Let’s take a look at some of the interchanges in and around the beltway, to see what they reveal. We will approach the city from the north on Maryland’s I-270. Here, that highway branches in two as we approach the beltway.
If we travel East on the beltway we come across this interchange near College Park where I-95 intersects the beltway. Original plans for Washington’s freeway system included an extensive network of urban freeways that were never built — this interchange was designed to accommodate a never-built leg of I-95 extending to the District. Today, University of Maryland officials are advocating a freeway connecting this interchange to their campus.
As we continue along the beltway we come to this recently rebuilt interchange between the Capital Beltway and Route 50 in Prince George’s County. This photo shows the close relationship between Washington’s freeway and Metrorail system. From the very beginning the systems were designed somewhat in tandem and the train was intended to carry visitors into the city after arriving this far by auto. Here, special onramps connect the beltway to the New Carrollton Metro Station.
Continuing around the beltway we encounter the Springfield Interchange, one of several interchanges around the country known popularly as “The Mixing Bowl.” Here the beltway intersects both I-395 and I-95, and the interchange was long one of the most dangerous stretches of the beltway. In 1999, the Virginia Department of Transportation began an 8-year project to re-design the interchange in a project that is currently estimated to cost in excess of $670 million before it is complete.
As we continue around we come to the last I’ve selected for inclusion — this interchange where the beltway meets Route 50/Arlington Boulevard.
Interchanges Elsewhere
Interestingly, perhaps because of the investment in Metro, the scale and number of the freeway interchanges in the region is not notable from a national perspective. This image of the Big Dig in Boston gives a good idea of the scope of that project.
Unlike Washington, the city of Detroit did actually construct the entire network of urban freeways planned for that city, including some truly massive interchanges like this one, between I-96 and the Southfield Freeway.
Much more is written about interchange design and the Washington region’s freeways elsewhere on the web, so I won’t go into detail here. What am I missing? What is your favorite (or least favorite) interchange in the region?
References
> Scott M. Kozel’s Roads to the Future (Transportation history for VA, MD, DC)
> Kurumi’s Field Guide to Interchanges
> Springfield Interchange Improvement Project
> Google Earth Community: Crazy Highway Interchanges thread
Not really in DC but I-70 stops abruptly after the Baltimore Beltway because of fears that it would destroy the environmental quality of one of that city’s only major parks:
http://www.google.com/maps?q=Baltimore,+MD,+USA&ie=UTF8&z=14&ll=39.303222,-76.692295&spn=0.040381,0.069351&t=h&om=1
Recently the area that had been planned for the roadway has given way to a major trail that takes riders from the park and ride (at the end of I-70) to downtown Baltimore:
http://www.gwynnsfallstrail.org/
On of my favorites is the I-95/I-695 interchange northeast of Baltimore. For both highways, the direction of traffic switches (traffic passes on the left instead of the right) through the interchange. Apparently, such an odd arrangement increases the speed with which one exits to the other highway in any direction:
http://www.google.com/maps?q=Baltimore,+MD,+USA&ie=UTF8&om=1&z=16&ll=39.350892,-76.497202&spn=0.007483,0.020084&t=k
I’d also recommend you take a gander at the Univ. of Maryland’s traffic research program. They’ve got cool diagrams and animations of unconventional intersections and interchanges, including the mesmerizing “Windmill” interchange:
http://attap.umd.edu/uaid_ags.php
well rob, they didn’t actually build all of the freeways in detroit. read about the davison (http://www.michiganhighways.org/listings/MichHwys01-09.html#M-008), which would have continued west to the jefferies, and north and east to mound round up to I-696. in fact, if you look at the mound round interchange with I-696, you can see where it was overbuilt to accommodate a freeway-to-freeway interchange there.
i LOVE interstate freeways!
Yes, the highway system in the DC area is very stunted. This is due to the NIMBY stance of everybody in the region. I grew up in Silver Spring and recently learned that the Inter County connector is FINALLY being built.
There are no expressways through the city [unless you wish to count DC-295], hence traffic congestion is notorious, with all motorists funneled towards a few Potomac River crossings, and the main surface level Avenues.
The most impressive interchange of the area is The Springfield Mixing Bowl. This is the confluence of 495-395-95. Other than that, the only notables are 495 / U.S. 50 and 495 / 295 / Indian Head Highway in PG County.
The stunted expressway system is what makes Washington, Washington. The cozy and quasi European feel of The District is what I am speaking of…
Although not all major freeway interchanges in terms of aesthetics:
Key Bridge approach: M Street / Key Bridge / Whitehurst Freeway.
14th Street Bridge: The ramps and design of 395 from Shirlington into Washington is technically sound while providing spectacular views of the Washington Monument, Jefferson Monument, Pentagon, etc.
US 29: The transformation of this roadway from a sleepy 2 lane north of New Hampshire Avenue into a limited access route is stunning, and is testimony to the strong economic development of the region.