TPB News

"Big Data" Unlock Possibilities for Better Understanding Congestion on Area Roadways

Jun 9, 2014

The Transportation Planning Board is taking advantage of the growing availability of real-time data on traffic conditions to better understand congestion on Washington area roadways.

In its most recent quarterly analysis, the TPB found good news for drivers and other road users over the past few years: a 40% decline in average congestion-related delay between 2010 and 2013. A trip that would normally take 30 minutes in traffic-free conditions took about 37 minutes on average in 2010, but just 34 minutes in 2013.

The recent analysis also examined the traffic impacts of last October's two-week federal government shutdown. It found that average delay on area Interstate highways dropped almost 17% during the shutdown compared to the weeks just before the shutdown began.

The TPB's quarterly congestion reports, among other studies and analyses, are made possible by the growing availability of anonymous travel speed information from GPS-equipped smartphones and in-vehicle navigation devices. The information is one example of large and complex data sets often referred to as "big data," which were previously unable to be collected or too complex to process with existing technology.

Private companies now gather the GPS-based speed information from drivers and other road users who have agreed to share it anonymously for traffic-monitoring purposes. Familiar services like Google Maps use the information to show real-time traffic conditions in their online tools and applications.

The speed data is updated as frequently as every 60 seconds around the clock for more than 5,500 lane-miles of Interstate highways, major arterial roadways, and local and neighborhood streets in the region. The data add to the suite of efforts the TPB uses to monitor traffic conditions and track changes over time, including periodic aerial surveys of the region's freeways and various other traffic counts and surveys.

The new data unlock a world of possibilities for better understanding congestion by allowing analysts to examine month-to-month, day-to-day, and hour-by-hour variations on more roads around the clock all year long.

A 2012 TPB report drawing on data from 2011 looked at changes in congestion-related delay that could occur during summer months, when schools are out, days are longer, and the weather is warmer. It found that average delay in July and August was about 20% lower than in June or September. It also found that total daily driving in the summer months was about the same as other times of year, highlighting the effect that changes in when people travel, not just changes in how much they travel, can have on traffic conditions.

In 2013, the TPB evaluated the traffc impacts of the opening of the Intercounty Connector (ICC) in Maryland. The report showed a drop in travel delay on local roadways in the vicinity of the ICC after the new highway opened in 2012.

Other applications of the data have included examinations of the traffic impacts of the August 2011 earthquake and various ice and snow storms, and improvements to the computer models the TPB uses to predict future travel patterns.

The TPB's quarterly congestion reports summarize monthly and daily traffic conditions in the region, highlight short-term changes in traffic conditions resulting from disruptive events like major accidents and severe weather, and identify key bottlenecks. They accompany a biennial report the TPB produces detailing efforts to monitor and evaluate the performance of the transportation system and to use strategies like transportation demand management, Intelligent Transportation System (ITS) technologies, emergency response coordination, and other approaches to mitigate delays.

Quarterly reports and links to other congestion-related analysis and reports can be found online at

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