Do people drive less because they live in buildings that don’t provide parking, or do they live in buildings that don’t provide parking because they drive less? That question has huge implications for how we build and rebuild our cities, yet researchers have struggled for decades to answer it conclusively. UCLA professor Adam Millard-Ball joins us to discuss new research that finally — we hope — puts the question to bed. Taking advantage of San Francisco’s affordable housing lottery, Millard-Ball and colleagues find that (as-good-as-)randomly assigning tenants to different buildings and neighborhoods has substantial impacts on their transportation choices, with lower parking ratios resulting in less driving and more transit use. We talk about what this means for housing and parking policy, and what it says about the behavioral shifts needed to make cities more affordable, accessible, and sustainable.