Major track work will cause major disruptions in downtown Portland for MAX and streetcar commuters starting at the end of the month.

The work along Southwest Morrison and Yamhill streets will upgrade some of the oldest sections of MAX tracks by replacing underground wooden ties, the track be and switch machines, as well as sections of the track itself.

But it means three weeks of disruption for several MAX lines, and two weeks for the Portland Streetcar.

TriMet is asking riders to consider alternatives to MAX, including its bus service, and to avoid bringing bulky items like bikes, suitcases and strollers on trains. All MAX trains will run less often, meaning riders can expect a longer wait and crowded cars.

Those who do take MAX, however, should tack on 30 to 45 minutes to their trips, the agency said.

The disruptions begin April 30. The Portland Streetcar will be diverted through May 13, and MAX through May 20.

Here are the details by line:

Portland Streetcar: The streetcar won't serve stops on 10th and 11th avenues.

The NS Line will run between Portland State University and the South Waterfront. A special route will run from Northwest 23rd Avenue along the eastside route, turning around at SW 10th & Clay/SW Park & Market.

A shuttle bus will serve most of the 10th and 11th avenue streetcar stops during the disruption.

A map of Portland Streetcar and shuttle bus routes during a disruption scheduled for April 30 to May 13.

MAX Blue Line: Trains will run between Hillsboro and Providence Park. There, riders can transfer to shuttle buses to the downtown Transit Mall. Trains also will run on the east side, but they'll be diverted to the Transit Mall, where they'll turn around at Portland State University.

MAX Red Line: Trains won't run between Beaverton and downtown Portland. Trains between Portland International Airport and downtown Portland will be diverted to the Transit Mall, and they'll turn around at Portland State University. Riders headed toward Beaverton can transfer to shuttle buses to Providence Park, where they can transfer to the westbound Blue Line.

MAX Green Line: Trains will run between Clackamas Town Center and Rose Quarter Transit Center, but won't cross into downtown Portland.

MAX Yellow/Orange Lines: No change in route, but trains will run less frequently.

A map of MAX and shuttle bus routes during a disruption scheduled for April 30 to May 20.

The work is one of several projects planned to shore up aging MAX infrastructure and improve reliability. The agency made similarly disruptive repairs along First Avenue in downtown Portland in last May and in the Rose Quarter in August.

-- Elliot Njus

enjus@oregonian.com

503-294-5034

@enjus