What is the primary effect of an ADU policy?

• A. Increases automobile traffic
• B. Increases housing supply and affordability by permitting additional units on existing lots
• C. Decreases property values
• D. Reduces zoning flexibility

Answer: (B)

The primary effect of an ADU policy is to increase housing supply and affordability by permitting additional units on existing lots. Allowing accessory dwelling units—such as backyard cottages, basement apartments, or garage apartments—lets more units be added within already developed areas, using land and infrastructure that are already in place. This expands the overall stock of homes and provides more affordable options for renters and buyers, often with lower construction or land costs than new detached homes. In most cases, the goal is to create more housing options without changing the neighborhood’s overall character or requiring new parcels of land. The other options describe potential secondary or incidental outcomes, but they’re not the policy’s main aim: traffic impacts, changes in property values, or shifts in zoning flexibility can occur but are not the core purpose of permitting ADUs.