Four thousand or more bicyclists will participate in the 38th annual 2026 Triple Bypass bicycle tour through the mountains of Colorado starting Saturday.

The Colorado Department of Transportation warns drivers to prepare for road closures and heavy bicycle traffic near Interstate 70 from Evergreen to Avon on Saturday.

The Triple Bypass is a popular annual cycling tour in Colorado that began in 1988 when a small group of cyclists organized a challenging one-day ride from Evergreen to the Vail Valley area. Now in its 38th year, it attracts thousands of participants each July for a roughly 120-mile route with more than 10,000 feet of climbing over three mountain passes: Juniper, Loveland and Vail.

It is known as a bucket-list event with aid stations, volunteer support and charitable fundraising components, drawing riders from across the country. A shorter Double Bypass option is also offered.

Bicyclists will travel U.S. 6 over Loveland Pass, and the highway will close to all motor vehicle traffic between 9 a.m. and 3 p.m., officials at the department said in a statement. Vehicles hauling hazardous materials will receive escorts through the Eisenhower/Johnson Memorial Tunnels during the closure, with westbound escorts at the top of the hour and eastbound at the bottom of the hour, according to a news release.

Additional road closures will take effect in Jefferson, Clear Creek, Summit and Eagle counties. Westbound Highway 103 from Bergen Park to Idaho Springs closes from 5 a.m. to 10 a.m., while eastbound Highway 103 from Idaho Springs to Bergen Park closes from 6:30 a.m. to 11 a.m. Local traffic will be permitted on Highway 103. Eastbound and westbound Alvarado Road between Lawson and the Easter Seals Camp closes from 6 a.m. to noon.

Drivers should anticipate additional cyclists on the Dillon Dam Road, Interstate 70 frontage roads through Vail and U.S. 6 between Dowd Junction west of Vail and Avon, even without full closures. The Colorado State Patrol and local law enforcement will monitor traffic.

The department reminded drivers to give bicyclists at least 3 feet of space when passing, even if it requires crossing the centerline when safe. Failing to do so risks a ticket under state law. Bicyclists must ride as far right as possible and avoid impeding traffic.

Travelers should check conditions before heading out through COtrip.org or the COtrip Planner app. The department also urged caution in work zones: obey speed limits, stay alert, watch for workers and allow extra space.