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June 3, 2019

Media Contact

Andrew Barth, 303-441-1032

Ironman Road Detours and Closures – June 8-9

The Ironman Boulder will return to Boulder County on Sunday, June 9. Images of course maps and detour routes are attached. Use the link at the bottom of this post to find links to view those maps in a larger format. Plan for increased travel times in some areas. Significant detour and heavy traffic is expected on SH 119/Diagonal Highway. All traffic will be shifted onto the Longmont-bound travel lanes to allow the bike course to use the Boulder-bound lanes.

The bike course will active between 7 a.m. and 5 p.m. and will use the following roads:

  • SH 119/Diagonal Highway
  • N. 63rd St.
  • Monarch Rd.
  • Niwot Rd.
  • Neva Rd.
  • U.S. 36/N. Foothills Hwy
  • Nelson Rd.
  • N. 65th St.
  • St. Vrain Rd.
  • Hygiene Rd.
  • SH 66/Ute Highway
  • N. 75th St./N. 73rd St.
  • 71st St.

All residents will have access to their homes, but may encounter delays. Event marshals will grant access to residents when safe to do so.

Travel Restrictions:

  • N. 63rd St. WILL BE CLOSED to vehicular traffic from Monarch Road. to SH 119/Diagonal Highway from 6 a.m. to 5 p.m.
  • N. 71st St. WILL BE CLOSED to all traffic from Monarch Road to SH 119/Diagonal Highway from 6 a.m. to 5 p.m.
  • Niwot Rd. WILL BE CLOSED to all traffic from SH 119/Diagonal Highway to 71st Street from 6 a.m. to 5 p.m.
  • Monarch Road WILL BE CLOSED from SH 119/Diagonal Highway to 71st Street and IBM East Loop Road to 63rd Street from 6 a.m. to 5 p.m. Access to IBM will be allowed via 71st Street to Monarch Road to IBM East Loop Road. NO ACCESS TO IBM VIA SH 119/Diagonal Highway
  • N. 51st Street will be closed from Jay Road to Monarch Road except to local residents between 6 a.m. to 6 p.m.
  • Boulder Reservoir will be closed all day on Saturday and Sunday, June 8 and 9.

Please use alternate routes around the course (i.e., U.S. 36, Oxford Road, and Airport Road).

All Ironman spectators must use the shuttle service from Boulder High School, no exceptions.

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

Avoid using Niwot, Nelson, or St. Vrain roads. Those roads will be open, but you will experience longer delays than if you use the loop around. 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.

Recreational cyclists should avoid traveling in the same direction as the riders on the bike course and avoid traveling on and across the SH119/Diagonal Highway between 55th Street and Oxford Road. The IBM Connector Trail will be open to maintain cyclist access across the course on the SH 119/Diagonal Highway. Recreational cyclists may use N. 63rd Street from Niwot Road to the IBM Connector Trail, but they may not cross SH 119/Diagonal Highway.

Please consult the interactive map for more information.

If you have questions or concerns, please email

You can also access more information at the event website: Click on the “spectators” tab for more info.

You may also contact John Holste, Boulder County Special Events Coordinator at

Detour route map for 70.3 Ironman