The annual Penn Relays started today, with the first running event held at 10 a.m. this morning at the University of Pennsylvania’s Franklin Field (see the full schedule here). The Penn Relays means thousands of guests on and around Penn’s campus, so we wanted to alert our readers to watch out for a lot of traffic and closed streets in the area.

33rd Street from South Street to Walnut Street will be closed for approximately one hour, on Saturday from 6 to 7 p.m., according to a traffic advisory by Penn Public Safety.

This Philadelphia institution is being held for the 120th time and will draw over 18,000 competitors from more than 60 countries to participate in 425 events. The event will be held through Saturday, April 26.