Alexandria, Virginia — The American South (Mid-Atlantic)
The Rail Yard Hump
City of Alexandria Est. 1749
— Potomac Yard —
Certain rail classification yards depended on a simple landform called the "hump." Potomac Yard had two humps: one for the northbound trains and one for the southbound trains. Trains first entered a receiving yard where locomotives were detached from trains and cars were sent to a classification yard over the hump: a hill built between the two yards. After being pushed to the top of the hump by a yard locomotive, cars were uncoupled in specific groups and allowed to roll down one of several different tracks to become part of a new train. This group of tracks formed the classification yard. This system used gravity—and a good deal of pre-planning by track managers—to make classifying (or sorting) rail cars much easier.
Potomac Yard incorporated numerous technological advances over the years to improve efficiency. Classifying cars evolved from primarily manual labor to utilizing automated and digital systems. Computers, installed at the Yard in the 1960s and 1970s, replaced mechanical relay systems with state-of-the-art digital systems.
The first hump yards at Potomac Yard
In the late 1950s, the hump yards were once again updated when the VELAC system was installed at the southbound hump. VELAC, an automated classification yard system, replaced remote switches with electronic switches controlled from a four-story concrete tower. Touted as an "electronic brain," VELAC made car classification even more efficient and required fewer employees.
Erected by City of Alexandria.
Topics and series. This historical marker is listed in these topic lists: Railroads & Streetcars • Science & Medicine. In addition, it is included in the Virginia, The City of Alexandria series list.
Location. 38° 49.355′ N, 77° 2.913′ W. Marker is in Alexandria, Virginia. Marker is at the intersection of Main Line Boulevard and Potomac Avenue, on the right when traveling north on Main Line Boulevard. The marker stands in the Potomac Yard neighborhood of Alexandria. Touch for mapTouch for directions.
Other nearby markers. At least 8 other markers are within walking distance of this marker. Crossroads of Transportation (within shouting distance of this marker); Potomac Yard in Transition (within shouting distance of this marker); The People of Potomac Yard (approx. ¼ mile away); The Alexandria Almshouse (approx. 0.3 miles away); Building Potomac Yard (approx. half a mile away); Potomac Town Hall and Firehouse (approx. half a mile away); Corporal Charles William Hill (approx. half a mile away); Smoot Lumber Company Planing Mill (approx. 0.6 miles away). Touch for a list and map of all markers in Alexandria.
Credits. This page was last revised on April 28, 2021. It was originally submitted on March 30, 2018, by Devry Becker Jones of Washington, District of Columbia. This page has been viewed 117 times since then and 8 times this year. Photos: 1, 2, 3. submitted on March 30, 2018, by Devry Becker Jones of Washington, District of Columbia. • Bernard Fisher was the editor who published this page.