As transportation chair of the Virginia Sierra Club, Stewart organized the I-66 Corridor Coalition, an alliance of seven organizations that advocated for a transit-first approach to improving I-66 outside the Beltway, and he coordinated grassroots support for Fairfax County’s 2014 transportation bond proposal, which provided more than $75 million for walking and bicycling facilities. Stewart is a co-founder and leader of Fairfax Advocates for Better Bicycling and Fairfax City Citizens for Smarter Growth.