Buses and light-rail trains, underground together. Rolling through the same tunnel. Loading and unloading passengers at the same subterranean stations.
It's never been tried anywhere. Sound Transit and King County Metro propose to do it in the 1.3-mile tunnel that has carried buses under downtown Seattle for the past 12 years.
Their plan is either the best use of the tunnel for the foreseeable future or a giant waste of its people-moving capacity. It's either too risky or no more dangerous than the way the tube is used today.
Sound Transit and its opponents have been debating the wisdom of buses and rails sharing the tunnel since last summer, when the agency embraced the idea as part of its scaled-back plan to build a 14-mile light-rail line from downtown to Tukwila by 2009.
Voters may be asked to decide who's right.
Sound Transit and King County, the tunnel's owner, reached agreement Friday on joint use. If it's approved by the County Council and Sound Transit's board, as expected, light-rail opponents have threatened to collect signatures to submit the deal to a referendum. If voters rejected the agreement, it could kill light rail. Sound Transit doesn't have another way to get trains downtown.
Each side in the bus-tunnel debate has produced studies that support its own conclusions. Each side has accused the other of cooking the books.
But they agree on this much:
• Sound Transit's plan would alter thousands of downtown commutes, beginning in 2007 when the tunnel closes for construction. When it reopens two years later, some transit users will enjoy shorter commutes. For others, trips downtown will take at least a little longer than before the tunnel closed.
• Joint bus-rail operations in the tunnel won't solve downtown's traffic problems. Sound Transit's opponents say it will actually make the situation worse. Sound Transit disputes that, but it also says downtown congestion will be about the same, with or without light rail. "We've never said we will reduce congestion," says Joni Earl, Sound Transit's executive director. "What we're about is another option, out of the congestion."
Here are questions and answers about what's planned and what's in dispute:
Q: I thought Sound Transit planned to convert the tunnel to exclusive light-rail use — no buses.
A: It did, until last year.
When voters approved a 21-mile light-rail line from the University District to SeaTac in 1996, backers held out joint bus-rail operations in the tunnel as a possibility.
But Sound Transit concluded in a 1998 study that rail-only operations made more sense. Joint operation posed safety problems, the agency said, and both rail and bus service would be significantly slower and less reliable. So Sound Transit signed an agreement in 2000 to buy the tunnel from King County in 2003.
All that happened before cost overruns pushed Sound Transit to scale back the light-rail line last year. As the project changed, joint use began to look more appealing.
A: The 14-mile "starter" line that's now planned is expected to attract just one-third as many riders as the original project. According to Sound Transit's forecasts, the number of people boarding trains in the tunnel daily in 2020 would actually be lower than the number of passengers boarding buses in the tunnel today. So reserving the tunnel for light-rail only was difficult to justify.
Sound Transit and Metro did another study of joint use last year and concluded it was much more feasible with the shorter rail line and fewer trains. Changing circumstances and new technology had eliminated or minimized the problems the 1998 study identified, they said.
Leaders of Sane Transit, the light-rail opposition group, say the agencies' change of heart was too convenient to be credible.
Q: Does Sound Transit still plan to buy the tunnel?
A: No. Under the new joint-use agreement, the county would retain ownership. Sound Transit would pay all the debt service on the tunnel during the two years it's closed, then pay 40 percent of the debt service and operating expenses after it reopens. That percentage would increase if Sound Transit's use of the tunnel increases.
The agreement also calls for Metro and Sound Transit to negotiate a contract that would name Metro the operator of the light-rail line. If there's no contract by next spring, Sound Transit would be required to buy the tunnel.
Q: How much of downtown's bus traffic does the tunnel handle now?
A: Metro says 132 buses run through it each weekday between 4:30 and 5:30 p.m., the busiest hour. They ferry about 2,500 passengers out of downtown and about half that number into the city during that hour.
The 132 buses in the tunnel amount to less than a quarter of the 593 north-south buses serving downtown during the peak hour. The other 461 travel on the surface.
Q: Why don't more buses use the tunnel?
A: Because Metro doesn't have enough of the right kind of buses. The ones that operate in the tunnel are custom-built, dual-powered models that run on diesel fuel most of the time, then switch to electricity from overhead wires when they go underground.
The agency hasn't bought any of those buses since 1990. It had planned to buy hundreds more but didn't because light rail was on the horizon.
Q: How much traffic will the tunnel handle when both buses and trains are running through it?
A: Sound Transit computer simulations indicate the tunnel can handle 10 trains and about 60 buses in each direction — that's 20 trains and 120 buses total — during the afternoon peak hour. That's almost as many buses as today, plus a train each direction every six minutes.
Sane Transit says those projections may prove overly optimistic when they're tested. Opponents haven't come up with numbers of their own.
Forecasts of the tunnel's capacity haven't always been accurate. When the tunnel was planned in the 1980s, Metro estimated it could handle 290 buses an hour. After more than a decade of operating experience, the agency now says the tunnel's capacity is 250 buses an hour.
Q: Will buses and trains share the tunnel indefinitely?
A: That's not the plan. Sound Transit and Metro say buses would be phased out as rail service increases. But they don't anticipate the tunnel would become all-rail until light rail is extended beyond Northgate.
Q: Why do they need to close the tunnel for two years for construction? Aren't there rails in the tunnel already?
A: Rails were installed in the tunnel when it was built in the late 1980s. But Sound Transit says it can't use them because they aren't adequately insulated. Stray electricity from the trains could escape into the earth and corrode metal pipes.
In addition to installing new rails, Sound Transit plans to lower the roadbed in the stations by six inches so passengers can walk or wheel themselves directly from the platform onto rail cars and onto new, low-floor buses without climbing stairs or using wheelchairs lifts. That should speed loading.
Sound Transit also plans to install new overhead electrical wires to power the trains, replace the overhead sprinklers with new ones on the tunnel's walls (the overhead sprinklers don't leave enough clearance for trains), install a new signal system to keep buses and trains separated and improve the emergency ventilation system.
Q: How much will all this cost?
A: About $62 million to $68 million, Sound Transit says. That's $37 million to $43 million more than the agency had planned to spend to retrofit the tunnel just for trains.
Q: Will both the trains and buses run on electricity from overhead wires?
A: Maybe not. Metro wants to replace the aging tunnel buses with hybrid buses that operate on both diesel fuel and stored electricity. Those buses wouldn't need wires.
Q: Is Metro interested in buying the hybrid buses only because it needs them — or something like them — for the tunnel?
A: Metro says it would be considering the hybrids regardless because they are more fuel-efficient and less polluting than standard diesel buses.
Is it safe?
Q: Is it safe to operate buses and trains in the same tunnel? What about collisions?
A: Sound Transit expressed concern about that when it rejected joint use in 1998. The agency said that, because the tunnel lacked a fail-safe signal system, it would be up to operators to maintain safe stopping distances.
Sound Transit and Metro now say they have developed a new signal system to keep buses and trains from occupying the same station platform or tunnel segment at the same time. While the new system still wouldn't be fail-safe, a train-bus collision would be highly unlikely, they concluded.
Sane Transit remains skeptical; there's no similar operation anywhere to learn from. Sound Transit says the signal system will be tested for three to six months before the tunnel reopens.
Q: What about fire safety?
A: Assistant Fire Marshal John Nelsen, who has reviewed Sound Transit's plans, says the tunnel is safe now and adding light rail shouldn't make it any less so.
Q: What will happen to the buses that now use the tunnel when it closes for retrofitting in 2007?
A: Sound Transit and Metro estimate there will be 148 afternoon peak-hour buses in the tunnel by then, 16 more than today. They'll be rerouted to the surface on Second, Third and Fourth avenues.
Q: What will that do to downtown traffic?
A: It will make it worse. The only question is how much.
Sound Transit, Metro and the city of Seattle plan to spend $13 million, mostly on surface improvements, to minimize the impact. Third Avenue would be closed to all traffic except buses and emergency vehicles from 6 to 9 a.m. and 3 to 6 p.m. Traffic-control officers would be stationed at key intersections.
Even so, Sound Transit says average delays at some intersections will increase from one to 20 seconds.
Most buses rerouted from the tunnel to the surface will take six to seven minutes longer to get from one end of downtown to the other, the agency calculates.
Sane Transit's technical advisers argue there will be more buses on downtown streets than Sound Transit and Metro assume — both while the tunnel is closed and after it reopens. As a result, they say, congestion will be worse than predicted (see accompanying story).
Q: What will happen when the tunnel reopens?
A: Most of the buses that were in the tunnel before will return. But they'll take longer to get through the tunnel because they'll have to wait in staging areas at the tunnel entrances when trains approach. The agencies say bus riders will experience an average delay of 1.5 minutes.
The wait could be longer, Sane Transit counters, if train and bus operations don't mesh as smoothly in the tunnel as Sound Transit's computer simulations indicate.
Q: How will the buses in the tunnel affect light-rail operations?
A: Metro and Sound Transit say trains will take about one minute longer to travel through the tunnel than if the tunnel were rail-only.
Q: Who will be riding the trains when the tunnel reopens?
A: Sound Transit says its two-car trains will carry about 1,800 passengers out of downtown during the afternoon peak hour in 2010, and 2,200 in 2020. Most will be headed for Southeast Seattle. Some will be former bus commuters.
Q: Will their commutes be shorter than now?
A: Rail should help many get to and from downtown in less time.
One example: Metro's current schedule shows that, during the afternoon rush hour, the 42 Express bus takes 31 to 34 minutes to get from Second Avenue and Pike Street downtown to the intersection of Martin Luther King Jr. Way and South Othello Street.
Sound Transit estimates it will take trains 22 minutes to get to the proposed light-rail station at that same intersection from Westlake Station downtown.
But there won't be nearly as many rail stations as there are bus stops, so some passengers may have a longer walk home if they switch to light rail. Sound Transit estimates more than 40 percent of its Southeast Seattle light-rail passengers will get to and from the train by bus; transfers could cost some commuters extra minutes.
Q: Will joint operations mean fewer cars on downtown streets?
A: The difference will be negligible. Sound Transit forecasts 34,000 morning rush-hour auto trips to downtown in 2020 if the 14-mile light-rail line is built, 34,400 if it isn't.
Q: What about buses? Will light rail take some of them off downtown streets?
A: Not many. Metro does plan to terminate some routes that now serve downtown at outlying light-rail stations, converting them to "feeder" routes.
But its tentative plan would eliminate just 15 afternoon peak-hour downtown buses when trains start running. Even in 2020, Sound Transit says, light rail won't have much impact on the number of buses serving downtown at rush hour.
Q: If light rail won't reduce the number of cars and buses downtown, how do Sound Transit's leaders justify it?
A: They say it will provide commuters an alternative to congestion, a new transportation corridor. They also say the benefits will be more dramatic when — if — the line is extended to Northgate, eliminating many more cars and buses from downtown.
Q: Do Sound Transit's critics have an alternative to joint use?
A: Sane Transit says the region would be served better if the number of buses in the tunnel were increased, and that buses have the potential to move just as many people as light rail. Sound Transit and Metro say committing the tunnel to all-bus use would be foolhardy over the long run.
Q: What about the short term?
A: The Downtown Seattle Association, which opposes joint use, has calculated that if the number of afternoon peak-hour buses in the tunnel were nearly doubled, to 250, they could carry slightly more passengers in 2010 than the 120 buses and 20 two-car trains proposed under joint operations.
Sound Transit's downtown light-rail manager, Mike Williams, doesn't contest that. But he says that, with 250 buses, the tunnel would be at capacity. The joint-use scenario could accommodate more growth, he says, because a third car could easily be added to the trains.
Sane Transit contends that, with some modifications, the tunnel's peak-hour bus capacity could be much greater than 250.
Q: In the long term, could more passengers move through the tunnel if it were all-rail or all-bus?
A: The two sides agree on the tunnel's rail-only capacity. They disagree on its bus-only capacity. Consultants to Sane Transit say bus-only and rail-only capacity are about the same. Sound Transit and Metro say the tunnel could accommodate only one-third as many peak-hour riders if it were all-bus.
Q: How did they reach such different conclusions?
A: By starting at different places.
In their capacity analysis, Metro and Sound Transit figured the number of buses in the tunnel would increase to 250 but assumed no other significant changes in the way the bus system operates.
Sane Transit's consultants assumed a bus system in 2030 that's very different from today's. For instance, they assumed buses would enter and leave downtown on exclusive busways or high-occupancy-vehicle lanes.
They also assumed bus service in the tunnel would be restructured to serve as a transit "spine," picking up inbound commuters at stops outside downtown served by "feeder" buses.
Sane Transit assumed every bus seat would be occupied, and that more passengers would stand in the aisles. Sound Transit and Metro assumed one bus seat in five would be empty.
Q: Couldn't we resolve this whole conflict by digging a second transit tunnel under downtown?
A: The state Department of Transportation is wrapping up a preliminary study of that notion, first suggested by downtown business interests. Study manager John Okamoto says a tunnel under Fifth or Sixth avenues is technically feasible.
The cost? "It's big," he says.
Eric Pryne can be reached at 206-464-2231 or firstname.lastname@example.org.