The 12th annual Escape from the Rock triathlon will take place Sept. 7, beginning at Luther Burbank Park.

About 800 participants are expected this year, who start at 8 a.m. with a half-mile swim in Lake Washington, followed by a bike ride across the I-90 express lanes and a 2.5-mile run through the streets of Mercer Island.

“We appreciate the relationship we have developed with Mercer Island during the past 10 years we put on this event,” said Michelle Ruettinger, a spokesperson for Envirosports, which organizes the event.

Participants can compete by themselves for all three legs of the race or compete as a team of two or three, splitting up the events.

During the run, participants use the pedestrian-and-bike path along I-90. Crucial intersections will have police or event marshals for safety. Event organizers ask that Islanders drive with reduced speed and caution while runners are present on the road.

“We are attempting to provide a safe environment for both Mercer Island residents and triathlon participants,” said Horning.

The following streets will be closed during the biking portion of the event:

• S.E. 24th Street between 81st and 84th Avenues S.E.

• 81st Avenue S.E. between 24th Avenue S.E. and North Mercer Way.

• North Mercer Way between 77th and 81st Avenues S.E.

• 80th Avenue S.E. between North Mercer Way and S.E. 27th Street.

Traffic will be restricted to local residents only on the following streets:

• S.E. 26th Street between 84th Avenue S.E. and North Mercer Way.

• 84th Avenue S.E. between S.E. 26th and 24th Streets.

• North Mercer Way between S.E. 26th Street and 81st Avenue S.E.

For more information on the event or to sign up go to www.envirosports.com.