Repairs to a troublesome section of track in downtown Portland will mean crowded trains and major delays for MAX commuters over two weeks in May.

The $2.1 million project is one of several planned in TriMet's effort to shore up its light-rail network's declining reliability. It will tear up and replace the section of track along First Avenue, one of its oldest stretches.

It will also improve drainage in a spot where standing water flooded MAX trains on Halloween last year, sidelining damaged vehicles for weeks.

But the work will mean diverting trains from May 8 through 21:

Red and Blue Line trains will run on the transit mall along 5th and 6th avenues.

Only Blue Line trains will run between Hillsboro and Library/Galleria MAX stations.

Green Line trains will run only between Rose Quarter Transit Center and Clackamas Town Center.

Yellow and Orange line trains will run their regular route.

Except for Blue Line trains, MAX lines will run on reduced frequency, with trains arriving every 20 minutes at peak hours. Blue line trains on the west side will run every 10 minutes during commute hours and every 15 minutes at other times.

TriMet says it expects trains to be crowded, especially during commute hours. Red and Blue line passengers passing through the Portland City Center should expect their trip to take an extra 30 to 45 minutes.

Last year was MAX's worst on record for on-time service, with one in five trips late. It's planned a series of repair projects to help speed up trains.

While the First Avenue project promises to be disruptive, more disruptive repairs are coming. Fixes in the Rose Quarter and Steel Bridge bottleneck could potentially disrupt every MAX line. That work is expected in the next couple of years.

-- Elliot Njus

enjus@oregonian.com

503-294-5034

@enjus