After Metro announced last week that it hopes to build a new loop line between downtown DC and Arlington, many people immediately started comparing it to the other cities that have transit loops. How would Metro’s line compare to the others?

There are actually a variety of loop types. Each type tends to operate differently and have different characteristics.

Graphic by the author. Click for the full version.

Very few lines operate as a true circle. Glasgow is one of the exceptions. Trains operate in both clockwise and counterclockwise directions. It’s a more urban-type circle. Moscow’s Koltsevaya line is another urban example. Berlin’s Ringbahn also operates as a circle, but it’s got a larger radius, and is more of a suburban-style circular line.

Other lines tend to act more as urban distributors, offering a convenient way to turn trains around and to serve larger areas of the central business district. Examples include the Chicago L Loop and loops in Sydney and Melbourne, which serve commuter trains.

Miami also has an urban circulator called Metromover. It operates in a very small circle downtown and mainly serves to distribute commuters from Metro to destinations around the CBD. Two other Metromover “loops” (not shown in the graphic) operate via the downtown loop, but are more linear in nature, continuing to the north and south of the CBD.

Next, we’ll look at how a DC Metro loop might work.

Matt Johnson has lived in the Washington area since 2007. He has a Master’s in Planning from the University of Maryland and a BS in Public Policy from Georgia Tech. He lives in Dupont Circle. He’s a member of the American Institute of Certified Planners, and is an employee of the Montgomery County Department of Transportation. His views are his own and do not represent those of his employer.