A traffic back-up on Montgomery Lane in downtown Bethesda Credit: Bethesda Beat file photo by Andrew Metcalf

Editor’s Note: The following view is that of the writer and does not reflect the opinions of Bethesda Beat staff. 

Building housing in downtown Bethesda, Westbard, and Chevy Chase Lake does not cause traffic problems. It solves them.

Traffic from Bethesda and Chevy Chase into Washington, D.C., has been on the decline for a quarter-century. There has been a small uptick in the last few years, but the number of cars on the road in 2015 (the most recent State Highway Administration data) was still 16 percent lower than in 1990. Traffic growth from 2011 to 2015, reported in a new Montgomery County Planning Board study, is due to falling gas prices and economic recovery; the long-term trend, in all likelihood, is still downward. 

Average weekday traffic volumes at counting stations closest to the District line 

Source: Maryland State Highway Administration

Why are fewer area residents driving into D.C.? There are surely many reasons. More of them are retired, work from home or telecommute. More work in the suburbs rather than D.C.

But those trends alone cannot account for the traffic drop. Over the past quarter-century, Montgomery County’s population grew from 765,000 to more than a million. The number of jobs in D.C. grew too, by more than 10 percent.  

Less crowded roads are the consequence of land-use trends. Since 1990, almost all new development inside the Beltway has been in walkable, mixed-use centers where people can reach many destinations on foot and use public transit for longer trips. There is less need to drive, and the car trips people do take are shorter.

To be sure, traffic trends farther out from the District have been less favorable. That’s because development there has been more spread-out, forcing people to drive longer distances. Housing in Bethesda adds little to upcounty congestion because Bethesda residents who commute toward the north are driving against traffic.  

Unfortunately, the tools our county uses to guide its planning do not reflect these realities. Planners use forecasting models that look at traffic one intersection at a time, and they measure how fast cars move rather than how long it takes to get to a destination. These models, widely criticized by experts, often predict trouble from transit-oriented building projects that will actually cut congestion.

River Road shows how far off the models can be. The 1990 Bethesda-Chevy Chase Master Plan includes a prediction of future traffic growth on this highway. Actual traffic levels near Ward Circle in Northwest Washington, D.C., in 2015 are less than half of what was predicted. Traffic on the road farther from the District has also declined, although not as much.

Predicted and actual weekday traffic volumes on River Road

Sources: Maryland State Highway Administration, Bethesda-Chevy Chase Master Plan, p. 121

The county’s traffic forecasting methods have improved since 1990, but they contain the same basic flaws. County law requires planners to use pseudoscientific concepts like “intersection delay” and “level of service” that measure how fast cars move and not how long it takes to get to one’s destination.  A 20-minute drive to the nearest store on a free-moving highway gets an “A” rating; a trip across the street is scored as “F” if cars back up at the corner for 90 seconds in rush hour.  

A regional housing shortage is driving up rents and pinching family budgets. Fortunately, the housing most in demand—near downcounty transit stations—is also the housing that adds the least to traffic. Misleading computer models should not deter us from building the homes our residents need.

Bethesda resident Ben Ross is a former president and current ex officio board member of the nonprofit advocacy group Action Committee for Transit and a blogger for Greater Greater Washington.

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