Report on Hwy. 520 bridge design 'not perfect, but it creates progress'

Several design changes could help buses, pedestrians and bicyclists move more easily in the Montlake area of the Highway 520 bridge, even with a smaller interchange than what is now proposed, according to a city consultant's report summary made available Wednesday.

Among other changes, the highway could use only six lanes across Portage Bay instead of seven, while reducing shoulders and ramps near Foster Island, says the five-page summary.

The report is "not perfect, but it creates progress on all the concerns we have," said City Councilman Richard Conlin.

The state is trying to replace the aging, four-lane floating bridge with a six-lane toll bridge, which would have two general-purpose lanes and one high-occupancy vehicle (HOV) lane in each direction. State law defines HOVs as transporting three or more people.

Most City Council members support the general strategy but have complained the state Department of Transportation (DOT)'s Montlake interchange design is too massive. Negotiations will continue the next few months, while the state prepares to construct the less-controversial Eastside and floating sections.

Some ideas, from consultant Nelson/Nygaard, appear on an unpublished map Conlin showed The Seattle Times on Wednesday. Options include:

• Instead of the seventh Portage Bay lane, which is intended for merging westbound traffic from the University of Washington to Interstate 5, use the shoulder for peak-time merging and I-5 exiting.

The state DOT resisted such dual-use shoulders when former Mayor Greg Nickels proposed them for a Highway 99 tunnel, but the state agency had no immediate comment Wednesday about the 520 report.

• Create two general lanes and one transit lane each direction between UW and 520, as well as traffic signals that give buses a head start.

• Build a second Montlake Cut drawbridge, but with only two vehicle lanes to keep the size narrower. City Councilman Mike O'Brien said Wednesday there ought to be traffic limits, maybe even tolls, on Montlake Boulevard Northeast so the new lanes don't just become clogged with more traffic.

• Scrap a proposed Sound Transit skybridge from the future Husky Stadium light-rail station, and go with the "Rainier Vista" alternative, where people would cross at a new Montlake Boulevard signal into the landscaped triangle, en route to the UW Medical Center or upper campus.

The city had urged the UW and Sound Transit to study alternatives because of a policy opposing skybridges, said UW spokesman Norm Arkans. Sound Transit has said 70 percent of pedestrians at the station would take a footbridge.

But Conlin said he favors a surface crossing — especially for bicyclists who would connect from the triangle to future bike routes along Montlake Boulevard and Highway 520.

• Limit traffic through the Washington Park Arboretum, just south of 520, by reducing speed limits, closing the Arboretum to cars on weekends, or even tolling Lake Washington Boulevard through the Arboretum.

• Reduce the shoulders to just more than 8 feet across Foster Island, so they can never be converted for car traffic — a major fear of O'Brien's. Doing so also would prevent a widening for future light rail, unless a new Union Bay Bridge were built for trains from the main 520 bridge to Husky Stadium, said Conlin.

Seattle Mayor Mike McGinn insists that light rail be running across 520 when the bridge opens in the mid- to late 2010s.

The state has shown interchange layouts as wide as 271 feet. Conlin said that would be reduced significantly, but that level of detail wasn't immediately available.

Mike Lindblom: 206-515-5631 or mlindblom@seattletimes.com