A tale of two (or three) rush hours: researchers track Silver Line traffic impact

July 29

Monday’s Silver Line opening did not measurably affect traffic congestion on surrounding highways in Northern Virginia, but researchers are gathering more data to determine impacts over coming days.

Below is a loop of traffic speeds for Monday’s morning and evening rush hours, compared with the previous Monday and the last Monday of July 2013, courtesy of Michael L. Pack, director of the University of Maryland’s Center for Advanced Transportation Technology.

Monday's weekday Silver Line opening did not measurably affect traffic congestion on surrounding highways in Northern Virginia, but researchers are gathering more data to determine impacts over coming days. This video shows a loop of traffic speeds for Monday's morning and evening rush hours, compared with the previous Monday and the last Monday of July 2013. (Courtesy Michael L. Pack, director of the University of Maryland's Center for Advanced Transportation Technology)

Speed measurements are drawn from anonymized data from GPS devices such as cell phones, vehicle navigation systems and monitoring devices in commercial vehicles such as taxis and delivery trucks. The legend at the bottom shows actual speed driven as a fraction of the “free flow” speed.

CATT archives data to help transportation departments measure the performance of roads in real-time and historically, calculate economic and environmental impacts, and prioritize and assess spending.

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