We know D.C. Get our free newsletter to stay in the know.

What’s the deal with bus letters and numbers? Some have a letter and a number, some have two numbers and a letter, some just have two numbers, while others have a letter and two numbers. I don’t really see a method to this madness.

“There could be a simple numbering system, but nobody is interested enough to demand it,” says Lawrence A. Glick, a Metrobus service planner who proposed a revamping of the system few years ago.

Instead, Metrobus’s numbering system is a hodgepodge of the four separate systems that were folded into the Washington Metropolitan Area Transit Authority (WMATA) in 1973.

In 1936, Capital Transit Company, the main District transit group prior to WMATA, began using characters to distinguish their routes. Streetcars featured two numbers—the tens digit identified the line, and the ones digit indicated the route; buses featured a letter identifying the line and a number indicating the route. Capital Transit numbered their streetcars in a clockwise arc from their origin—starting with a route beginning in Rosslyn that was numbered 10 and 12, a Cabin John line numbered 20 and continuing to a U Street/Florida Avenue route numbered in the 90s. They applied letters to bus routes in a counterclockwise arc beginning in Southeast Washington. However, the pattern was not entirely consistent—the 16th Street lines were designated with an “S.” For both streetcars and buses, the even-numbered lines indicated all-day service, while odd numbers denoted rush hour or part-time service.

As for the other companies later incorporated into WMATA, Washington, Marboro & Annapolis Motor Lines (WMA) used a letter to designate its lines and a number to distinguish different routes within a line. The two Virginia companies—Alexandria, Barcroft & Washington Rapid Transit (AB&W) and the Washington, Virginia & Maryland Coach Company (WV&M)—both used a numbering system that had letter suffixes to indicate route variations. After the merger, WMATA added a tens digit to the former WMA routes to avoid duplication with Capital Transit lines and kept the WV&M’s numbers the same while renumbering AB&W’s numbers.

As a result, in the former Capital Transit service area—encompassing the District, Montgomery County and western Prince George’s County—Metrobus routes have two-digit numbers where they follow streetcar lines that lasted into the ’50s and a letter-and-number format on former Capital Transit bus lines and on streetcar lines that were converted to buses prior to 1950.

“When we number new routes, we try where we can to keep to the old system that applied to whichever side of the river the route serves, but constraints in the original D.C. and Maryland numbering systems have created a number of exceptions to the old patterns,” says Glick.

Every Monday, the ‘Huh?’ Bub takes your questions. Got one?