High-Risk Corridors
US 36, US 287, and the Diagonal Highway
Boulder's heaviest transit and bus traffic moves along U.S. Route 36, the Denver-Boulder Turnpike that runs through the city on 28th Street, and along Colorado State Highway 119, the Diagonal Highway expressway connecting Boulder and Longmont. Boulder County's Vision Zero program records repeated head-on, speed-related, and curve-related crashes on the US 36 and US 287 corridors and on Colorado 119. The 28th Street and Arapahoe Avenue intersection alone saw roughly 30 accidents at or near it in 2022 through early December, per city reporting. The county recorded 22 traffic deaths in 2023, 19 in 2024, and 17 in 2025.