Boulder County published a news release on Thursday morning highlighting traffic impacts, detours, and travel restrictions in the area.
Boulder County, Colo. - The IRONMAN 70.3 Boulder event will return to Boulder County on Saturday, June 14, 2025. The event takes place in the area north of Boulder, south of Lyons, and west of Longmont.
All residents will have access to their homes, but may encounter delays and should follow recommended detours. View the interactive course map and detour routes.
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 7 a.m. and 2 p.m. on Saturday, June 14, and will use the following roads: CO 119/Diagonal Highway, N. 63rd St., Monarch Rd., Jay Rd., US 36/N. Foothills Hwy, H 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 Hygiene. 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
- Hygiene 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 7 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, and CO 66 to get around the bike course. Please do not attempt to get across on Hygiene Rd., 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.
Shuttles
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.
Spectators will have shuttle access to the reservoir from 4a.m. to 10 a.m. (athletes will have priority) on Saturday June 14, 2025. Shuttles will be return spectators and athletes until 6 p.m. on Saturday June 14, 2025. Please understand that you will not be able to ride a shuttle into the reservoir after 10 a.m. Thank you for your understanding.
Parking/Shuttle Pick-up
- Kyndryl Boulder (Former IBM Building) 6300 Diagonal Hwy Boulder, CO 80301. You must access from CO 119/Diagonal Highway.
Shuttle Drop-off
- Boulder Reservoir 5565 North 51st St Boulder, CO 80301
Visit the event website for more shuttle and spectator 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 starting at 11 a.m. on Thursday, June through Saturday, June 14. No watercraft of any kind will be permitted into the Boulder Reservoir all day starting Thursday, June 12 through Saturday, June 14.
Additional Questions Or Concerns?
If you have questions or concerns, please email [email protected]. You may also contact John Holste, Boulder County Special Events Supervisor at [email protected].
View the event website for more information.
