It was an idea that made sense in Oregon and Utah: A temporary commuter train network set up to relieve traffic congestion while a major freeway is rebuilt.

The only difference is the Oregon Department of Transportation was able to pull it off.In Utah, for a variety of reasons, visions of commuter rail running parallel to the I-15 reconstruction corridor have not materialized and probably won't until well after the freeway is rebuilt.

And in Oregon, it was not a 51-month, 17-mile road revamp that officials were dealing with. The shutdown of the northbound I-5 bridge connecting Portland with Vancouver, Wash., was scheduled to last just three weeks.

Still, the success of the ODOT traffic management plan - which also included high-occupancy vehicle lanes, expanded bus service and an existing light-rail mass transit system - energized the effort to bring perm-a-nent commuter rail service to the Portland area.

A year ago this month, ODOT closed the northbound portion of the Interstate Bridge to replace a cracked trunnion, the axlelike mechanism that lifts and lowers the 81-year-old bridge. Transporting commuters and interstate travelers across river during the shutdown was a formidable challenge.

"We get about 50,000 residents from Vancouver who work in downtown Portland, so the big push was getting folks from Portland to Vancouver in the afternoon," when those commuters would normally take the northbound I-5 bridge, said ODOT spokesman Ron Scheele.

The department used moveable concrete barriers to turn the southbound portion into a two-way artery with reversible lanes. That allowed for two lanes of traffic into Portland in the morning and two into Vancouver in the evening but only one lane in the other direction.

Many commuters decided to avoid bridge delays by taking Amtrak trains, which departed Portland and Vancouver three times during both the morning and evening rush hours and carried up to 700 passengers each. Bus ridership increased 40 percent and the number of light-rail passengers jumped 20 percent during the project, according to ODOT.

As a result, I-5 bridge traffic, normally about 120,000 vehicles a day, was nearly cut in half. The traffic delays, according to Portland media accounts, were much less severe than expected.

As it turned out, ODOT crews managed to complete their work over the course of a week and two weekends. Only five commuter days were affected.

And just how much effort did it take to temporarily change commuter habits?

"We had six months of planning with nine public agencies working on this transportation plan," Scheele said.

In Utah, the Wasatch Front Regional Council already was exploring commuter rail as a transportation alternative when Utah Department of Transportation Executive Director Tom Warne wondered publicly if passenger trains could reduce the impact of I-15 reconstruction. At that time, in February 1997, Warne optimistically hoped a commuter train system between Provo and Salt Lake City could be in place within 18 months.

The needed enthusiasm and cooperation from Union Pacific Railroad, however, did not develop. Burlington Northern Santa Fe did allow ODOT to use its tracks - but only for a three-week period, and the state had to pay $225,000 to use the track.

Doug Hattery, a transportation engineer for the Wasatch Front Regional Council, said the key to ODOT's success was the short-term nature of the I-5 project. Congress set aside $4 million that could have been used for a commuter rail project paralleling I-15, but that money wouldn't have gone far, Hattery noted.

"We didn't want to run something for a couple of months and then have to shut it down," he said.

In retrospect, Warne now believes commuter rail was not as important for I-15 reconstruction as he thought before the work began.

"People have not flocked to public transit as an alternative," said Warne, whose statement is backed up by the Utah Transit Authority's sluggish ridership figures. "People have determined they are basically going to work around construction and adjust their schedules and patterns, and people have largely stayed in their automobiles as a way to handle the construction activity."

To Warne, that's an indication that UDOT and its I-15 reconstruction contractor are managing traffic effectively - making detours and closures bearable - while rebuilding the freeway.

In Portland, meanwhile, several permanent commuter rail routes are planned for locations where tracks already exist, including a Portland-Vancouver line similar to the one that enjoyed temporary success. An 18-mile, six-station line between two suburbs, Wilsonville and Beaverton, also could be up and running long before Utah has a commuter rail service of its own.

"One of the major driving forces (behind commuter rail) is that the alternatives have priced themselves out of the market," said Ed Immel, ODOT's state rail planner. "Like building freeways. Who can afford that in an urban area? And even light rail, unless you have a natural right-of-way," can be expensive.