A section of Kelly Drive will be off-limits to cars for three days because of the Dad Vail Regatta.
The closure, between Strawberry Mansion and Fountain Green Drives, was scheduled to start at 10 this morning.
Reopening is set for 8 p.m. Saturday.
Traffic heading toward Center City will be detoured south up the Strawberry Mansion Drive ramp to Reservoir Drive, south to Fountain Green Drive, then west back to Kelly, according to police.
Outbound traffic, will be routed east on Fountain Green Drive to Reservoir Drive, north to Strawberry Mansion, then north on the Strawberry Mansion Drive ramp back to Kelly.
Parking is available at remote lots, with shuttle buses running all day to and from the races, according to the Dad Vail website.
The Dad Vail Regatta is the nation's biggest collegiate rowing event, bringing thousands of student competitors from across the United State and Canada to Philadelphia the second weekend of every May.
The regatta is named for Harry Emerson "Dad" Vail, a college coach in Wisconsin who helped the sport grow in the early 20th century.