The RipRoar Triathlon will cause limited access and road closures from 7:30 a.m. to noon Saturday Aug. 17.
The triathlon will take place in and around Terra Park with swimming in Terra Lake, the bike portion on Pioneer Parkway and the run portion on the Terra Park trails.
Pioneer Parkway from Northwest 62nd Avenue on the west to Greendale Road on the east will be closed beginning at 7:30 a.m.
The City of Johnston Public Works, Fire and Police Departments will be helping to control the crowd which is expected to be around 1,000 participants and those cheering on the participants.
Swimming is not allowed before or after the race.
More information about the triathlon can be found on the RipRoar website.