Bicycle Stress Map

Montgomery County, Maryland, is using traffic-stress data to determine how biking comfort affects connectivity.

Few cycling thoroughfares in Washington, D.C., are fully protected from traffic. They’re packed with rushing cars, people backing out of driveways, and shape-shifting bike lanes, when any actually exist. As a daily bike commuter, I can attest that these factors can make cycling pretty harrying, which in turn discourages a lot of other people from doing it. And research shows that fewer cyclists means riskier streets.

Just north of D.C., transportation planners in Montgomery County, Maryland, are taking a systematic approach to breaking this vicious cycle. With a new Bicycle Stress Map, county planners have quantified and mapped the “traffic stress level” of the county’s bike network, assigning a numeric value and corresponding color to every street and bike trail.

Based on methodology developed by the Northeastern University transport scholar Peter Furth, the planners calculated those “TSL” values based on traffic speed and volume, the number and width of car and bike lanes, parking turnover, how easy it is to get through intersections, and other characteristics. A quiet, residential road with a low speed limit—which Montgomery County is full of—would be rated low-stress (blue), comfortable enough for most adults and kids. On the other end of the spectrum, a broad, multi-lane boulevard with a 40-mile-per-hour speed limit—even with a bike lane—would be rated high-stress (red) and might deter all but the most hardcore cyclists.

Cyclists can adjust the map to view the streets that fit their personal comfort levels. And local transportation planners are using the map as they develop the county’s Bicycle Master Plan. As explained on the map’s website: “When a street has a moderate or high level of stress, it may be a sign that bicycle infrastructure, like separated bike lanes or shared-use paths, is needed to make it a place where more people will feel comfortable riding.”

The map makes one thing strikingly clear: Most Metro stations in Montgomery County are accessible only to cyclists who can tolerate relatively high stress levels. The same is also true for Capital Bikeshare stations (though those aren’t visible on the map). Working with the map and the underlying data, Stephen Tu, a planner with Montgomery County, and Alex Rixey, of the transportation consultancy Fehr & Peers, have identified a number of only moderately stressful streets that, with the addition of just a few low-stress connections (likely in the form of protected bike lanes), could significantly expand connectivity and accessibility to Metro and bikeshare stations for cyclists. Though their work is still in the preliminary stages, it points to a more data-driven approach to creating reliable bike transit.

“Knowing the level of traffic stress gives you a way of evaluating how successful your bike infrastructure projects will be,” Rixey tells CityLab. “We can show what kind of connectivity you can get from a few million dollars of investment.”

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