Drivers Sunday will want to take particular care on roads winding from downtown St. Louis all the way to the Western reaches of St. Louis County, as bicyclists hit the pavement.
They're supporting Pedal The Cause, the annual fundraiser that benefits local research at the Siteman Cancer Center, the Washington University School of Medicine, Barnes Jewish Hospital and Children's Hospital.
Courses open as early as 7 a.m. Sunday morning.
You can find specific turn-by-turn courses for the event on the Pedal The Cause Website
Organizers have warned participants that this is a ride, and not a race, per se, and that the event is taking place on open roads.
The MICDS campus as well as the Siteman Cancer Center at Barnes West County Hospital are among "refueling stations" for the ride.
Not all roads will be closed as part of the race.