From TriMet.org:

MAX Service Interruption for Steel Bridge Construction August 2-24, 2008


What's happening?
The Steel Bridge will be closed to MAX Light Rail trains from Saturday, August 2, through Sunday, August 24, 2008, as crews connect existing tracks to the new MAX Green Line tracks on 5th and 6th avenues.

Shuttle buses will be running between the Rose Quarter/Convention Center stations on the east side of the river and Old Town/Chinatown Station on the west side.

The lower deck of the bridge will be open for pedestrians and cyclists.

Your travel options
During the closure, you have several options for getting across the river.

1. Shuttle: 15-30 minutes
TriMet shuttle buses will be available to take you across the river. Shuttles will be running frequently (every 1-4 minutes during peak travel times) between the Rose Quarter/Convention Center stations and Old Town/Chinatown Station.

If you take the shuttle, plan ahead to allow an extra 15-30 minutes for your trip. (See "Tips for Shuttle Riders" below.)

2. Walk: 15 minutes
We recommend walking across the bridge, if you can. On average, it will take you 15 minutes to walk between the Rose Quarter and Old Town/Chinatown stations. Follow the signs to the pedestrian/bike route (see map) on the lower deck of the bridge. Stay on the marked path, as it's the fastest and safest route.

3. Bike: 7 minutes
If you bring your bike on MAX, you should ride your bike across the bridge. It only takes about 7 minutes to bike between Rose Quarter and Old Town/Chinatown stations. Shuttle buses take longer and have limited space for bikes. Follow the signs to the bike route on the lower deck of the bridge. Stay on the marked path, and be considerate of other users.
Important information for cyclists using MAX during the Steel Bridge closure

We're here to help!
TriMet staff will be on hand to help, and signs will direct you to shuttle buses and pedestrian/bike paths. If you have questions, email us at customerservice@trimet.org or call 503-238-RIDE (7433).

Riding MAX from the east side
Blue and Red Line riders
Get off at Convention Center Station and board a shuttle bus to Old Town/Chinatown Station. At Rose Quarter TC, Blue Line trains will turn back, heading east to Gresham. Red Line trains will turn north, becoming Yellow Line trains traveling to the Expo Center.

Yellow Line riders
Stay on MAX (past the Interstate and Rose Quarter stations) and get off at Convention Center Station, where you can board a shuttle bus to Old Town/Chinatown Station. Yellow Line trains will travel south to Interstate/Rose Quarter Station, then turn east, becoming Red Line trains bound for the airport.

Riding MAX from the west side
Blue and Red Line riders
Get off at Old Town/Chinatown Station and board a shuttle bus to Rose Quarter TC. There, you can catch a Blue, Red or Yellow line train. Due to operating constraints, MAX will be running less frequently on the west side between BTC and downtown Portland.

Yellow Line riders
There will be no Yellow Line service on the west side of the river. Board any eastbound train and transfer to a shuttle bus at Old Town/Chinatown Station. The shuttle will take you to Rose Quarter TC, where you can catch a Blue, Red or Yellow line train.

Going to the airport?
You don't have to wait for a "Red Line" train: All eastbound trains will connect with the shuttle at Old Town/Chinatown Station. Throughout the bridge closure, the last Red Line train to the Airport will leave Rose Quarter TC at 11:07 p.m. on weekdays and 11:11 p.m. on weekends.

Tips for shuttle riders
Plan ahead: You should allow an extra 15-30 minutes for your trip, depending on the time of day.
Shuttles will be running every 1-4 minutes during peak travel times.
Don't worry about showing your fare to the operator. (Shuttles travel in Fareless Square.)
In the Priority Seating area at the front of the bus, move for seniors and people with disabilities.
Consider adjusting your work hours to avoid the crowds in peak travel times (7:30-8:30 a.m. and 4-5:30 p.m.).