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Thursday, October 23, 2003 - Page updated at 03:15 P.M.
Monorail panel weighs single track for 2-way traffic
By Mike Lindblom
The Seattle Monorail Project board is considering whether to build portions of the proposed 14-mile Green Line with just one track.
Northbound and southbound trains would have to take turns using the single-track areas. They could pass at the stations, using track switches to shift from double- to single-track areas. Or they could pass in dual-track areas elsewhere.
Sophisticated computers would be needed to keep the automated trains from colliding.
Single tracks would be a significant change from the traditional monorail concept, where two tracks run side by side.
The motivation for single-tracking is mainly to reduce the bulk and shadow of a larger elevated system in neighborhoods, said board Chairman Tom Weeks.
Another motivation is to save money on a $1.75 billion project whose tax income is one-third below expectations. A preliminary monorail issue paper suggests that more than $200 million in cuts will be needed.
Single-track areas would probably save money because there would be less need for massive underground foundations compared with dual tracks, which increase the bulk as well as torque and seismic forces.
The downside is that the monorail would probably never achieve the performance of double-track systems such as the Vancouver SkyTrain, where trains routinely arrive every 90 seconds at rush hour and every two to four minutes at other times. Joel Horn, the monorail's executive director, has instructed engineers to aim for arrivals every 5 minutes.
The system's people-moving capacity would be reduced, although Horn said the Green Line should still be able to meet the goal of 3,000 people per hour per direction promised in last year's voter-approved monorail plan.
A monorail board committee yesterday voted to proceed with more studies. Officials acknowledged the inquiry would slow the environmental-impact process and planning schedule, but they hoped to make up for the slowdowns through easier construction.
Monorail opponent Henry Aronson predicted this would be just one of a cascading series of reductions as the tax-revenue shortages hit.
"One can only guess what the next cuts will be as costs predictably exceed the projected costs," Aronson said.
The idea gives the term "mono"-rail a whole new meaning.
In Japan, The Monorail Society's Web site shows a system outside Tokyo, the Shonan Monorail, that is predominantly single-track. Five Japanese monorails have some single-track segments, according to the Cascadia Monorail Co., one of the two rival construction teams for the Seattle project. The team is offering Hitachi trains and says that more than 100 switches are operating safely in Japan.
The rival Team Monorail, which touts Bombardier trains and experience on the Las Vegas Monorail, says that single-tracking is technically feasible.
"Our goal is to figure out how efficiently it could be done, and at what cost," said Dick McNamara of Transmax, part of the team.
The main problem would be an excessively long "headway" or intervals between trains, he said. Another concern is a Ballard monorail bridge: Although train breakdowns are extremely rare, it would be frightening for passengers to be stuck far above ground without a rescue train available on a parallel track, he said.
However, the switching technologies are feasible and there should be no added risk of train collisions, McNamara said.
For most of this year, the monorail agency was touting the idea of monorail "irises" bi-level columns that allowed trains to dock with stations or buildings on one side of the street.
But both contracting teams complained that irises would add tens of millions of dollars to the cost. Monorail staff members initially dismissed the remarks as posturing, but in confidential meetings two weeks ago, they asked the teams whether single-tracking was possible.
A year ago, Craig Norsen, then a member of the monorail board, quietly suggested a similar idea. In particular, he thought a single track would be easier to fasten onto the existing West Seattle Bridge. But working on a fast timeline with limited funds, the group didn't have time to study single-tracking, so it placed a traditional side-by-side alignment in the formal plan for voter approval, Norsen recalled yesterday.
Weeks, the chairman, said an ideal place for single tracks is at the end of the line around California Avenue Southwest in West Seattle, where ridership from the Morgan Junction terminus is expected to be relatively low. Along Avalon Way Southwest, a densely populated condominium area, a lone track would reduce the bulk that has worried residents, said Vice Chairwoman Kristina Hill.
The north terminus at Crown Hill is another possibility but single tracks could hinder future capacity if the Green Line is ever extended to Northgate, monorail board candidate Cleve Stockmeyer pointed out.
Downtown may not be suitable for single-tracking because it is likely to be the area of heaviest use. Also, the bulk of the switches might outweigh the benefit of smaller beams and columns there.
But monorail officials said they haven't ruled it out.
Several landowners have objected to what they consider the visual blight of a monorail on Second Avenue, and some have proposed building the project only from Ballard to Westlake Center and from West Seattle to King Street Station, with no tracks through downtown.
Single-tracking compromises the option of making the Green Line the trunk of a longer system.
"To do a regional system and even propose something like this is completely ridiculous," said light-rail partisan Richard Borkowski of People for Modern Transit. Sound Transit's light-rail plan offers almost unlimited capacity and near-freeway speeds in its elevated and tunneled dual-track segments, but is limited to lower speeds in the downtown bus tunnel and on the surface in Rainier Valley.
But Hill says a single-track plan would allow future monorail segments to be extended into neighborhoods where they otherwise would not fit.
"What we're creating is the potential for expansions into tighter settings, whether it's Boren, 45th or some other street," Hill said. "This is much more efficient."
Mike Lindblom: 206-515-5631 or email@example.com
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