Animated map shows congestion by the hour

John Aaron,

WASHINGTON – An interactive map is taking the guesswork out of — what can sometimes be — a grueling commute.

If you’re trying to weave your way through Capital Beltway traffic, check out the animated map that shows how bad congestion is, on average, for each hour of the day and each day of the week.

Rahul Nair, of the Center for Advanced Transportation Technology (CATT) at the University of Maryland, says it’s the result of billions of readings from speed sensors on cars.

On the map, each section of the Capital Beltway is represented by a thin bar. Black portions of the bar mean speeds of less than 15 mph. Speeds of 60 mph and above are represented by green, with orange and red representing speeds in between 15 and 60.

The map would show, for instance, that on the Outer Loop in Maryland, ahead of the American Legion Bridge, traffic is terrible on Fridays around 5 p.m. Congestion eases significantly by 9 p.m., before getting bad again.

While some spots are consistently bad, others are unpredictable. It’s these spots that planners hope to address.

“Drivers do not like high variability,” Nair said.

“There are days when travelers do not know whether it’s going to be 15 minutes of 45 minutes. That sort of uncertainty is particularly bad because people tend to remember their worst commutes.”

Being aware of historical trends can help people make better decisions about how to get around. Most importantly, it can help transportation leaders reduce congestion through things like better work zone planning and incident response times.

Work zones were an unexpected finding of the study. If you stop the map’s animation at Saturday at 12 a.m., “you can see very slow speeds

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