Amergin,
It's just that Portland has for some time been upgrading and repairing a number of its bridges over the Willamette (accent on the second syllable) River, which runs right through the middle of the greater Portland area.
The Ross Island Bridge has had many of its on and off ramps closed for months (years?)--some of them all the time and some of them only at certain hours. Thus, for example, you can go over the bridge at, say 7:00PM and try to return home via the same route an hour later, only to find the ramp is closed and you have to drive a very circuitous route to get back across the river.
It's not that this is the only construction going on or the only affected bridge, but the similarity of "Rock Island" and "Ross Island" inspired someone at a song circle recently to suggest that someone should write a parody of "Rock Island Line" about the Ross Island Bridge.
Sonja