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August 4, 2021

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Rick Hackett, 720-564-2605

Ironman Boulder 70.3 race in Boulder County on Saturday, August 7, 2021

Residents and travelers in the race area should plan for detours and increased travel times

Boulder County, Colo. - The Ironman Boulder 70.3 returns to Boulder County on Saturday, August 7, 2021. Travelers in the area should expect delays, and some roads will be closed during the event.

Residents will have access to their homes during the event, but may encounter delays and should follow recommended detours. If you are traveling through the area during the event please pay close attention to the Boulder County Sheriff, Colorado State Patrol, and the volunteer traffic marshals who will be helping to ensure safety for riders and travelers alike.

View the course maps and recommended detour routes, or view an interactive map at

Travel restrictions and closures

The bike course will be active between 7 a.m. and 2 p.m. on Saturday, August 7, and will use the following roads:

  • CO 119/Diagonal Highway, N. 63rd St., Monarch Rd., Niwot Rd., Neva Rd., US 36/N. Foothills Hwy, Nelson Rd., N. 65th St., St. Vrain Rd., Hygiene Rd. CO 66/Ute Highway, N. 75th St./N. 73rd St., and 71st St.
  • Significant detour and heavy traffic is expected on CO 119/Diagonal Highway, though it will remain open to through traffic from Boulder to Longmont. All traffic will be shifted onto the Longmont-bound travel lanes to allow the bike course to use the Boulder-bound lanes.
  • N. 63rd St. WILL BE CLOSED to vehicular traffic from Monarch Road. to CO 119/Diagonal Highway from 6 a.m. to 5:30 p.m.
  • N. 75th St WILL BE CLOSED to northbound vehicular traffic between Hygiene and Hwy 66 from 6 a.m. to 2 p.m. Residents will be allowed to enter their neighborhood, NO ACCESS TO CO 66 from Hygiene.
  • N. 71st St. WILL BE CLOSED to all traffic from Monarch Road to CO 119/Diagonal Highway from 6 a.m. to 2 p.m.
  • Niwot Rd. WILL BE CLOSED to all traffic from CO 119/Diagonal Highway to 71st Street from 6 a.m. to 2 p.m.
  • Monarch Road WILL BE CLOSED to all traffic from CO 119/Diagonal Highway to 71st Street from 6 a.m. to 2 p.m. Access to IBM will be allowed via 71st Street to Monarch Road - NO ACCESS TO IBM VIA CO 119/Diagonal Highway.
  • Hygiene Road WILL BE CLOSED from Hwy 36 to 75th St from 6 a.m. to 2 p.m. Residents will be allowed to access their homes.
  • Nelson Road WILL BE CLOSED from 65th St to 75th St from 6 a.m. to 2 p.m. Residents will be allowed to access their homes.
  • N. 51st/55th Streets WILL BE CLOSED to vehicular traffic from Jay Road to Monarch Road except to local residents between 7 a.m. to 2 p.m.
  • Boulder Reservoir WILL BE CLOSED all day on Friday and Saturday, August 6 and 7, as well as the afternoon of Thursday, August 5.

Please avoid crossing the course, if possible. If you need to get from one side to the other, please use US 36/N. Foothills Highway, CO 66/Ute Highway, Jay Road, Airport Rd., and/or Hover Road to get around the course.

Please avoid using Niwot Rd., Nelson Rd., or St. Vrain Rd. While these roads will remain open for resident access, you will experience longer delays than if you use the loop around the bike course. Law enforcement will be at all major intersections to help you turn or move through the race course, but you should expect delays if you are crossing the route.

When passing a bicyclist, motorists must allow at least three feet of space between their vehicle and a bicyclist. To pass a bicyclist safely, drivers may cross a double yellow center line when oncoming traffic is clear.

Spectator shuttles

Beginning at noon on Thursday August 5, Boulder Reservoir will be closed to everyone except those with an Ironman access pass. Boulder Reservoir will reopen to the public on at 7 a.m. on Sunday, August 8.

All Ironman spectators must use the shuttle services to Boulder Reservoir from 7 a.m.-2 p.m. on Saturday, no exceptions. Athletes and spectators arriving before 7 a.m. and after 2 p.m. must have a valid access pass or utilize the shuttle services.
Shuttle Stops:

  • Boulder High School – 1604 Arapahoe Ave, Boulder
  • Boulder Marriott – 2660 Canyon Blvd, Boulder
  • Holiday Inn Express – 4777 N. Broadway, Boulder
  • Hampton Inn Boulder North – 6333 Lookout Rd., Boulder

Recreational cycling impacts

Recreational cyclists should avoid traveling in the same direction as the riders on the bike course and avoid traveling on and across the CO 119/Diagonal Highway between 55th Street and Oxford Road. The IBM Connector Trail will be open to maintain cyclist access across the course on the CO 119/Diagonal Highway. Recreational cyclists may use N. 63rd Street from Niwot Road to the IBM Connector Trail, but they may not cross the race course at CO 119/Diagonal Highway.

More information

View more information on the event website:

For questions, email, or contact John Holste, Boulder County Special Events Coordinator at

2021 Boulder Ironman bike course map2021 Boulder Ironman run course map2021 Boulder Ironman Niwot area detour routes map2021 Boulder Ironman Hygiene area detour routes map