Getting from Point A to Point B by car has taken longer than usual during SafeTrack, and while people changed when they commute during some of the work surges, few changed their actual routes. Those are two of the key takeaways from an analysis of rush hour congestion during SafeTrack that came out on Monday.

Increases in travel times along roads in the Washington area during the morning and afternoon commutes during each of the four SafeTrack surges so far. All images from the TPB.

The report comes from the National Capital Region Transportation Planning Board, whose analysts looked at hour-by-hour data on traffic conditions both this year and last.

Now a month and a half into its 10-month plan to to perform major maintenance across the system, Metro’s work has focused on four areas: there was single tracking between Ballston and East Falls Church in early June, a total shutdown between Eastern Market and both Minnesota Avenue and Benning Road later in the month and into July, and after that two shutdowns from National Airport, first to Braddock Road and then to Pentagon City.

You might not be surprised to see that freeway congestion, which the TPB measured by the percent increase in travel time, went up significantly during each surge. However, congestion increased much less outside on non-freeway arterials, which suggests that not very many people changed their routes to avoid the increased freeway traffic.

In addition, all four surges led to significant increases in travel times within downtown DC. These increases, even when Metro service in DC was not cut too significantly, are probably because more people drove to downtown offices.

While all four surges resulted in increased congestion, the increase was significantly larger for Surge 1 (single-tracking between Balston and East Falls Church) than for the other surges.

Change in freeway congestion for each surge, compared to the same dates in 2015.

The smaller increase in congestion from the later surges may have been due to the fact that the number of commuters generally goes down during the summer, as well as the fact that commuters were more aware of the later surges. However, it will be interesting to see how Surge 5, starting this week, affects congestion, since it will be a repeat of Surge 1.

A comparison of freeway congestion during Surge 1 to congestion during the same dates in 2015.

It’s worth noting the difference between changes in the intensity of the peak period congestion—which simply represents more cars on the road—and changes in the time distribution of congestion, which suggests that a significant number of drivers adjusted their trips to take into account the real or perceived effect of the Metro shutdowns and single-tracking.

Surges 1 and 4 mostly resulted in increased intensity of peak period congestion, while surges 2 and 3 seem to have resulted in more changes to commuters’ schedules.

What else do you notice in the image and graphs?