CNT In the News

Zoning in most Cascadian cities is anti-climate. Single-family zoning—the most sprawling residential zoning type—plasters swaths of the region’s urban areas. Seattle is prime offender: over half of its land is covered by single-family zoning. Bellevue, Bellingham, Eugene, Portland, Salem, and Spokane are similarly strangled by sprawling single-family zones. And the list could go on.

The consequence of having widespread, outdated zoning laws that mandate unwalkable city designs is that people drive more, and emit more greenhouse gases from their tailpipes. Cars are the largest source of greenhouse gas emissions in Seattle, as in other Cascadian metro areas. Myriad factors influence this relationship. For example, low-density neighborhoods lack the customer base needed to expand transit networks and grow neighborhood walkability via local businesses, reducing opportunities for car-free trips.

Accessory dwelling units (ADUs) could help dial down cities’ climate-busting design with minimal change to the physical form of single-family neighborhoods. These small homes, tucked into existing daylight basements, above garages, or in backyard cottages, make room for more people to join established single-family neighborhoods with very little impact on an area’s look and feel. Added up across the city, these homes nudge up residential convenience and walkability, cutting household driving, and attendant carbon emissions. The additional households bring the riders that support better transit service. They purchase the croissants, handmade cards, and children’s books that keep neighborhood businesses humming and in range of car-free travel options, like biking and walking. In turn, all residents of ADU-rich neighborhoods benefit, enjoying more robust transit, as well as a more thriving local business scene, and of course, the opportunity to make a few more trips car-free.

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Why Seattleites in certain neighborhoods drive less
The chart below shows annual household driving estimates for each of Seattle’s census block groups according to a predictive model from the Center for Neighborhood Technology Housing and Transportation Affordability Index (H+T).

CNT’s model estimates household driving behavior in every census block group in the United States using statistical relationships derived from measured driving behavior data in a variety of US urban and rural settings...