Many drivers and bus riders face major changes in Downtown traffic patterns starting this morning.

Because of subway construction, much of the Stanwix Street-Liberty Avenue intersection will be closed for a year. The closure will detour 27 Port Authority bus routes and many stops will be relocated.

Although the authority announced the changes last week, "I'm not sure people realize their routes might be affected," authority spokesman Jim Ritchie said yesterday. "Riders need to take a minute to check the routes that are being changed for the next year."

Westbound Liberty Avenue will be blocked off before it reaches Stanwix Street. Eastbound Liberty Avenue traffic will be required to turn right at Stanwix. Stanwix will be closed to through traffic.

At the same time, Penn Avenue will reopen to one lane of westbound traffic through Stanwix Street and the construction zone. No turns will be permitted from Penn onto Stanwix.

Affected bus routes are AV Allegheny Valley Flyer; AVN Allegheny Valley North Flyer; B Bellevue Flyer; OV Ohio Valley Flyer; CO Coraopolis Flyer; 3L Creighton-Lower Burrell Express; 3M Tarentum Natrona Express; 18B Avalon-Shadeland Express; and 18C Bellevue-Union Avenue.

Also, 26E Robinson; 28E Robinson Express; 28K Moon Express; 28M Campbells Run Express; 28X Airport Flyer; 31D Bridgeville-Washington Avenue; 31E Bridgeville-Main Street; 33D Bridgeville-Washington Avenue Express; 33E Bridgeville-Main Street Express; and 33X West Busway.

Also, 71A Negley; 71C Wilkinsburg-East Liberty; 71D Hamilton; 81A Oak Hill; 81B Lincoln; 81C Webster; 93A Aspinwall-Cheswick Express; and 100 West Busway.

Details of the route revisions and relocated stops can be found online at portauthority.org.

The changes also are described in brochures placed on buses and schedule racks, Mr. Ritchie said.

The intersection is being closed to accommodate reconstruction of the Gateway Center Light Rail Transit station, part of the authority's $538.8 million North Shore Connector project, scheduled for completion in late 2011.

The station will close with the departure of the final outbound trip at 1:21 a.m. on Oct. 31 and remain closed until the connector project is finished. Rail service will end at Wood Street.

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