A new study by the D.C. region’s Transportation Planning Board staff shows that while population has grown in recent years and fewer people are riding Metrorail, there has been no corresponding increase in automobile traffic.

Where is everybody? The chart atop this posting shows that Metrorail ridership on weekdays is at its lowest level since 2006. Yet vehicle miles traveled on weekdays, a standard measure of motoring, has been relatively flat for the past seven years.

The slow recovery from the Great Recession is certainly a factor in keeping a lid on commuting, but “it’s not just one thing,” said Kanti Srikanth, the board’s director of transportation planning.

Among other factors are declines in the size of the federal workforce. Also important are generational shifts, particularly the retirement of car-commuting Baby Boomers and the entry into the workforce of Millennials less inclined to drive to work.

But another very powerful thing that shows up in the Regional Travel Trends study is the increasing ability of the region’s entire workforce to telecommute.

“Work is less a place you go and more something you do where you’re at,” said Robert Griffiths, the board’s director of planning and programming.

Consider how we began this century. According to the data compiled for the Travel Trends study, population and employment in the D.C. region increased by 9 percent from 2000 to 2007. Weekday vehicle miles traveled grew by 18 percent. Metrorail ridership increased by 19 percent.

Then comes the watershed. Between 2007 and 2014, the study says, population increased by 13 percent and employment increased by 2 percent. Meanwhile, Metrorail ridership declined by 4 percent.

While transportation officials often say that a Metrorail commuter is taking a car off the road, a commuter’s decision to abandon Metrorail wasn’t necessarily adding a car.

As weekday Metrorail ridership was declining, vehicle miles traveled on weekdays dropped 1 percent overall. (Bus ridership increased about 1 percent in the period, and commuter rail ridership increased by a robust 22 percent, but MARC and VRE still account for a small portion of the overall commuting population in the region. Bike commuting gained steadily, but accounted for slightly less that 1 percent of the region’s commuters.)

An even more noteworthy measure of the trend in driving shows up in the chart that addresses vehicle miles traveled per person.

VMT per capita increased by 8.5 percent from 2000 to 2007, according to the study. From 2007 to 2014, it decreased by 10.5 percent. (Partial data suggest a slight uptick for 2015.)

While the overwhelming majority of the region’s commuters still drive to work, peak period congestion decreased by 6.5 percent between 2010 and 2013, according to the study.

Now consider the dramatic growth in telecommuting during the early part of this century. The study notes that the share of commuters teleworking at least occasionally increased
from 11 percent in 2001 to 27 percent in 2013. The third chart shows that.

The final chart, based on data from the 2013 State of the Commute study done for the planning board, shows the percentages of commuters who said they either did telecommute at least occasionally or who knew they could do so if they chose.

Overall, the 2013 study found, about half of commuters were at least potential teleworkers. When you know that, you know something about how we get through some of the big events that disrupt commutes, such as the pope’s visit last fall, the winter storms and the one-day shutdown of Metrorail.

The chart breaks down the actual or potential telecommuters by how they travel. A remarkable 86 percent of commuter rail users could telecommute. The high number may reflect the fact that so many commuter rail users live a long way from work and like the option of teleworking, at least occasionally.

Still, the MARC and VRE riders represent a relatively small portion of the overall number of commuters.

Metrorail riders account for a much larger share of the overall commute. And among them, 71 percent have at least the potential to work remotely.

Some separate research by the planning board staff on the one-day Metrorail shutdown in March suggests that the people who were able to shift from Metrorail to telework had a particularly significant role in saving the region from a disastrous commute on that day.

And even when Metrorail riders decide they just don’t want to take transit, they may be choosing to work from the comfort of home rather than heading for the highways.