News Archive

June 6, 2023

Media Contact

Andrew Barth, 303-441-1032

Ironman Boulder 70.3 race in Boulder County on Saturday, June 10, 2023

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

Boulder County, Colo. - The Ironman 70.3 Boulder race will return to Boulder County on Saturday, June 10, 2023.  Please plan for detours and increased travel times in the vicinity of the race.

All residents will have access to their homes, but you may encounter delays and should follow recommended detours. View an interactive map, or course maps and more information on the Ironman Boulder 70.3 website.

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. 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.

Travel Restrictions

The bike course will active between 6 a.m. and 2 p.m. and will use the following roads: CO 119/Diagonal Highway, N. 63rd St., Monarch Rd., Jay Rd., US 36/N. Foothills Hwy, St. Vrain Rd., and N. 75th St./N. 73rd St., and 71st St.

  • CO 119/Diagonal Highway will remain open, one lane of westbound/Boulder bound lanes will be closed from N. 63rd St. to Jay Rd. Expect delays.
  • Jay Rd. will be closed to westbound traffic from Diagonal Highway to 28th St.
  • US 36/28th St. will be closed northbound from Jay Rd. to St. Vrain Rd. Through traffic on northbound US 36 from Boulder to Lyons should use CO 119 to Longmont, head north on Hover Rd., then west on CO 66. If heading to Estes Park, use the same route or you may also use CO 119 to Nederland, then north on CO 72 to CO 7, then continue north to Estes Park.
  • 75th St./73rd/71st St. will be closed southbound from Hygiene Rd. to Niwot Rd. Niwot Rd. will remain open for local access, expect delays
  • St. Vrain Rd. will be closed to through traffic, residents will be allowed to access their homes
  • Monarch Rd. will be closed from 55th St. to 71st St. Residents will be allowed to access their homes via. 55th and 63rd Streets.
  • 63rd St. will be closed from Diagonal Highway to Niwot Rd. from 6 a.m. until 5 p.m. Residents will be allowed to access their homes from Niwot Rd., but there will be no access to CO 119/Diagonal Highway.
  • 51st/55th St. will be closed to through traffic from Niwot Rd. to Jay Rd. Residents will be allowed to access their homes.
  • Do not try to cross the course. If you need to get from one side or the other use US 36 Southbound or N. 75th St. Northbound, CO 66, and Hygiene Rd. to get around the bike course. Please do not attempt to get across on Niwot Rd., Nelson Rd., St. Vrain Rd., Plateau Rd., or westbound Jay Rd. While those roads will remain open for resident access except for as mentioned above, you will experience longer delays than if you use the loop around the bike course.


All athletes and spectators must take a shuttle on race morning (unless carpooling with a volunteer). There is no alternative method to getting to the venue. Visit the event website and click on the “Parking/Shuttle Info” tab for complete information.

Recreational Cycling Impacts

Recreational cyclists should avoid traveling in the same direction as the riders on the bike course.

Boulder Reservoir Impacts

Boulder Reservoir will be closed to the public Thursday, June 8 at 11 a.m. through Saturday, June 10. No watercraft of any kind will be permitted into the Boulder Reservoir ALL DAY Thursday, June 8 through Saturday, June 10.

For More Information

More information can be found at the event website. For questions or concerns, email or John Holste, Boulder County Special Events Coordinator at

Bike and Run Race Course Maps

2023 Ironman Boulder 70.3 bike race course map

2023 Ironman Boulder 70.3 bike run course map