The Richard S. Caliguiri City of Pittsburgh Great Race, the 36th to be held, will begin today at 8 a.m.
It has resulted in road closures and transit detours in Downtown, Oakland and Squirrel Hill.
Some 15,500 runners are registered to particate in the 5K and 10K events.
The 5K race begins at Fifth Avenue and Atwood Street in Oakland at 8 a.m.; the 10K run begins at Beechwood Boulevard near Frick Park at 9:30 a.m.
Road closures are expected at various times starting at 5:30 a.m. and concluding by 1 p.m. on sections of Beechwood, Dallas Avenue, Forbes Avenue, Morewood Avenue and Fifth Avenue, the Boulevard of the Allies (including its Oakland entrance ramp) from Fifth Avenue to Commonwealth Place; Wood Street from Allies to Fort Pitt Boulevard; Fort Pitt Boulevard from Wood Street to Commonwealth Place; Stanwix Street from Fort Pitt to Allies, and Commonwealth Place from Allies to Fort Duquesne Boulevard, including the blockage of Fort Pitt Bridge ramps at Liberty. Gateway Center in its entirety will be closed to traffic.
More than 30 Port Authority bus routes will be detoured. Details are posted on the authority's website, www.portauthority.org.
Also, Red Line rail service will be detoured because of construction at the Dormont Avenue grade crossing. Red Line trains will operate via the Blue Line between Overbrook Junction-Willow and South Hills Junction. A rail shuttle will operate between Overbrook Junction and Dormont. Bus shuttles will operate between Dormont and Fallowfield. Another rail shuttle will connect Shiras and South Hills Junction.