When the region's Metrorail system shut down all day on March 16 there was lots of potential to snarl area roadways -- by pushing those who normally take Metro to switch to driving instead. But a recent traffic analysis by the Transportation Planning Board confirms a general view among commuters, officials, and other observers that it wasn't nearly as bad as it could have been.

In its analysis, the TPB started by looking at traffic volumes on area freeways on the day of the shutdown and comparing it to normal traffic conditions. The analysis found that volumes were up 10-20% compared to the two previous Wednesdays in March. This is consistent with anecdotal observations that at least some of the 700,000 or so trips Metrorail carries on a normal weekday were diverted onto area roadways.

More: Read the full analysis of travel impacts of the March 16 Metro shutdown

In spite of the higher-than-normal volumes, however, the analysis found lower-than-normal travel delay on a regional scale throughout most of Wednesday. The average regional Travel Time Index (TTI), a measure of the extra time needed to reach one's destination because of traffic, was the same or lower than normal for all but a few hours of the day. (Although overall congestion was down, there were localized instances of higher-than-normal congestion.)

The main reason for the disparity: many motorists actively sought to avoid the day's worst traffic. Some left earlier or later than normal to avoid peak hours while others chose alternative routes in hopes of avoiding back-ups. Leaving home early was a particularly popular tactic. The TPB's analysis found that the regional TTI was about 8-13% higher than normal between 6:00 and 7:00 a.m.

The bigger story told by the March 16 Metrorail shutdown is the region's increasingly apparent ability to adapt to major disruptions in the travel system -- with enough warning. The March 16 event is one of a few recent examples of people altering their travel plans or avoiding travel altogether to minimize the effects of disruptive events, be it severe weather, large public events, or major operational disruptions like the Metro shutdown.

Last September's visit by Pope Francis brought the expectation of high demand on the Metro system and area roadways, prompting widespread decisions to allow employees to telework or take the day off. Metro also offered supplemental rail and bus service to handle additional crowds. Similar steps were taken during the region's historic blizzard in January. Early forecasts of the impending snowstorm gave officials time to make important decisions to close work places, issue travel warnings, and shut down transit services.

One exception that also helps tell the story is the light but extremely impactful snowfall of January 20, two days before the historic blizzard. Although less than an inch of snow fell, notice of the snow came too late in the day to prevent thousands of rush-hour commuters from hitting icy roadways at the same time. The ill-timed snow and icing event caused extreme delays that stranded thousands of motorists and bus passengers well into the night. 

More: Travel Impacts of the Pope's Visit, Quantified

More: Transportation impacts of the January 2016 snow events

These recent examples, diverse though they are, are tied together by a common thread: early warning. With the right amount of advance notice, the region has demonstrated an ability to adapt to major disruptive events. An increasingly diverse array of travel options gives people other ways to get where they need to go. Flexible work schedules and telework-friendly workplaces allow others to adjust their time of travel, or avoid traveling altogether. Planners caution that the adjustments people make during high-profile events are not changes they would be able or willing to make on a regular basis, which limits their promise for solving the region's broader daily travel challenges. But it helps highlight the region's resilience in the face of disruption, and that's something that serves the region well.