Alaskan Way Viaduct Replacement Tunnel

[Sub-Urbanite]

There's nothing to agree with in regards to induced demand. It's a known and documented phenomenon that needs to be considered when you have a limited amount of money to fix transportation problems. The Everett situation is a perfect example of induced demand, as the newly expanded road filled right back up, though now there's a HOV bypass for those who are smart enough to buddy-up for a commute.

Amen. Let's not argue with science here. There's solid data. That's not to say that every freeway will induce demand and become filled to capacity, but it's clear that the majority of freeway expansion projects will ultimately cause more people to use the speeded-up highway.

Side note — Read some research a few years ago that light rail also induces demand. Same concept — people shift from car to train, freeway gets faster, other people take freeway. So, basically, it becomes a game of figuring out how to move the most people as efficiently as possible, knowing that there is a set limit on what the freeway can do for you.

[kkt]

There are bars and restaurants along Alaskan Way.  Not being able to get to them by car or taxi would really hurt their business, I think.  For a fun evening out, a lot fewer people are willing to take bus or light rail than they would for work or errands.

[AlexandriaVA]

People take Metro out to events in DC all the time on nights and weekends, as do service-sector employees. It's much less of a big deal than you're making it out to be, and on the balance it will cut down on DUIs.

[AsphaltPlanet]

There's nothing to agree with in regards to induced demand. It's a known and documented phenomenon that needs to be considered when you have a limited amount of money to fix transportation problems. The Everett situation is a perfect example of induced demand, as the newly expanded road filled right back up, though now there's a HOV bypass for those who are smart enough to buddy-up for a commute.

Amen. Let's not argue with science here. There's solid data. That's not to say that every freeway will induce demand and become filled to capacity, but it's clear that the majority of freeway expansion projects will ultimately cause more people to use the speeded-up highway.

Side note — Read some research a few years ago that light rail also induces demand. Same concept — people shift from car to train, freeway gets faster, other people take freeway. So, basically, it becomes a game of figuring out how to move the most people as efficiently as possible, knowing that there is a set limit on what the freeway can do for you.

Demand can be induced with anything.  In a fictitious world, if a new high speed rail line was built between Seattle and Portland, it would spur new demand that wasn't there before that service opened.

In a freeway context, even if demand is induced by a freeway widening project, mobility is also increased.  So if, for example, a new lane was added to a freeway in an effort to ease congestion which becomes filled up in a few years, there are now capacity for 2000 additional trips per direction, per hour.

Demand induction is a real thing, and should be factored in as a decision in transportation planning initiatives, however, the increase in mobility may not be irrelevant, even if the level of service isn't significantly changed.

[jakeroot]

There are bars and restaurants along Alaskan Way.  Not being able to get to them by car or taxi would really hurt their business, I think.  For a fun evening out, a lot fewer people are willing to take bus or light rail than they would for work or errands.

But an 8-lane expressway between downtown and the waterfront shops could stand to hurt business just as much. We're trying to make this a walkable area.

Besides, you can still park a couple blocks up and walk down to the waterfront. There's no parking along the waterfront anyway, except below the viaduct, and I think both the current roadway and those parking lots are going to be merged into the future, much wider Alaskan Way. AFAIK, there's no plans for parking along the roadway anyway. The only parking options are private lots adjacent to the waterfront, and those won't last long once the waterfront is finished, due to increased land values.

[jakeroot]

There's not many Alaskan Way businesses that rely on personal car traffic in the first place. Tourist attractions will be easy enough to walk to without a giant freeway in the way (and especially with new options like the 1st Avenue streetcar opening in 2020 or so), and actual working industries will use trucks that could be given special access (seen in places like Manchester, UK where there is a network of bollards guarding truck/bus zones).

I quite like the bollard idea. Obviously, Alaskan Way would need to be shrunken down considerably for that to work, but, if personal vehicles weren't allowed (beyond like ride-share), there wouldn't need to be more than two lanes in each direction (one for transit, the other for delivery vehicles, taxis, etc).

The only potential problem I see is with taxis at the Cruise Ship Terminal, but we could easily enable them to use the new Alaskan Way. Or run shuttle buses. Or restore the Waterfront Streetcar.

My primary ship concerns are the Bremerton and Bainbridge ferries. I know I already mentioned the ferries, but it's an issue that would seriously need to be ironed out for the "no personal vehicles" idea to work. The good news is that the ferries all dock south of Marion, so there'd need to be personal vehicle accommodation from that point south, but the true waterfront doesn't start until north of Marion anyway, so I don't think that would be a big deal.

The cruise ships shouldn't be too big of a deal, because their garages are accessed from Elliott. And of course taxis and ride-share could be accommodated along Alaskan Way, so those who don't drive could still access the ships.

[Alps]

Induced demand is a fallacy. Very few trips are generated that weren't there before. They are coming from other modes and other streets. People completely ignore side streets and alternate routes, focus on the freeway filling up again, and claim that the demand was "induced." The best way to phrase it is "undisplaced." This is traffic that wanted to use the freeway before but couldn't due to capacity, so had to select alternate routes or make different lifestyle choices (i.e. going to a closer but lower quality destination, telecommuting, trip chaining, alternative modes). You're not building a freeway in a congested urban environment and suddenly people say "oh, let's go drive on the freeway." No, they always wanted to, but were unable.

[compdude787]

Induced demand is a fallacy. Very few trips are generated that weren't there before. They are coming from other modes and other streets. People completely ignore side streets and alternate routes, focus on the freeway filling up again, and claim that the demand was "induced." The best way to phrase it is "undisplaced." This is traffic that wanted to use the freeway before but couldn't due to capacity, so had to select alternate routes or make different lifestyle choices (i.e. going to a closer but lower quality destination, telecommuting, trip chaining, alternative modes). You're not building a freeway in a congested urban environment and suddenly people say "oh, let's go drive on the freeway." No, they always wanted to, but were unable.

Totally agree with this. The only people who drive on a road "because it's there" and not to get to a specific destination are roadgeeks trying to clinch it, people checking out a newly built road for the first time, and people who want to drive on a scenic route.

[kkt]

Or they chose to locate their house far from their job because there's a convenient freeway between them.

[Alps]

Or they chose to locate their house far from their job because there's a convenient freeway between them.

That demand is taken from somewhere else, then.

[compdude787]

Setting aside my opinion (and that of Alps) that induced demand is a fallacy, if Alaskan Way Viaduct is going to remain four lanes as it is now, why would induced demand even be a concern if the road is not going to be widened beyond its present configuration?

[jakeroot]

Setting aside my opinion (and that of Alps) that induced demand is a fallacy, if Alaskan Way Viaduct is going to remain four lanes as it is now, why would induced demand even be a concern if the road is not going to be widened beyond its present configuration?

Alaskan Way is only 2 lanes for most of its southern half, and has been configured as so for several years.

[compdude787]

Setting aside my opinion (and that of Alps) that induced demand is a fallacy, if Alaskan Way Viaduct is going to remain four lanes as it is now, why would induced demand even be a concern if the road is not going to be widened beyond its present configuration?

Alaskan Way is only 2 lanes for most of its southern half, and has been configured as so for several years.

Oh yeah, that's right.

[bing101]

https://www.youtube.com/watch?v=Z1uf1d7ta1M


Freewayjim did a tour of the Alaska way viaduct and some updates of construction for a tunnel at the time.

[compdude787]

Good idea to post that video! It will soon become historical documentation. I subscribe to Freewayjim as well as many other people like him (and am planning on making some road videos of my own), so I've already saw it, but it's good to post it for those who haven't seen it. WARNING: Watching road videos is a great way to waste a bunch of time.

[Alps]

Setting aside my opinion (and that of Alps) that induced demand is a fallacy, if Alaskan Way Viaduct is going to remain four lanes as it is now, why would induced demand even be a concern if the road is not going to be widened beyond its present configuration?

Alaskan Way is only 2 lanes for most of its southern half, and has been configured as so for several years.

Oh yeah, that's right.

Whether you believe in it or not, induced demand is much less a problem when widening a street on an existing urban grid. Getting to the downtown is the trouble. As long as existing Alaskan Way isn't a bottleneck (which I don't believe it is), while it may draw some traffic off of other parallel streets, it's not going to free up all the approach routes that would be needed to draw new demand to the downtown.

[jakeroot]

Setting aside my opinion (and that of Alps) that induced demand is a fallacy, if Alaskan Way Viaduct is going to remain four lanes as it is now, why would induced demand even be a concern if the road is not going to be widened beyond its present configuration?

Alaskan Way is only 2 lanes for most of its southern half, and has been configured as so for several years.

Oh yeah, that's right.

Whether you believe in it or not, induced demand is much less a problem when widening a street on an existing urban grid. Getting to the downtown is the trouble. As long as existing Alaskan Way isn't a bottleneck (which I don't believe it is), while it may draw some traffic off of other parallel streets, it's not going to free up all the approach routes that would be needed to draw new demand to the downtown.

There is one omission from the tunnel design that is different from the current viaduct: no downtown exits or entrances. This means that cars going to and from the south will need to use Alaskan Way to enter or exit the Hwy 99; essentially, Alaskan Way will become a giant on-/off-ramp. Right now, traffic (destined for downtown) exits at either Seneca or, less likely, Western, and can enter from Columbia or Elliott. Everyone else passes through the Battery Street tunnel and turns around, or gets off waaayy down south near Spokane Street and traverses 1st or 4th Avenues. An Alaskan Way that has signalized connections to most/all east/west named streets, and has direct access to the tunnel, will end up serving a whole lot more traffic than it does now because present-day Alaskan Way terminates at a T-junction with 1st Ave. A widened Alaskan Way won't induce demand in a way that brings more cars downtown, but it will encourage more cars to use Hwy 99 + Alaskan Way, versus Spokane Street Viaduct + 1st or 4th Avenues.

[jakeroot]

Err, on second thought, guess we don't have a choice but to maintain 4 GP lanes along Alaskan Way. WSDOT signed an agreement with the Port of Seattle that, in exchange for $300M in funding, guaranteed four lanes of GP traffic along Alaskan Way (see pages 3 and 4 at the link).

The only two options would be either (A) refund the Port of Seattle's $300M of funding in exchange for an MOU that basically tells the port to piss off, or (B) ban general traffic along Alaskan Way, but permit trucks, which should still make the Port of Seattle happy (but perhaps not fit the contract in the exact manner requested).

[Alps]

There is one omission from the tunnel design that is different from the current viaduct: no downtown exits or entrances. This means that cars going to and from the south will need to use Alaskan Way to enter or exit the Hwy 99; essentially, Alaskan Way will become a giant on-/off-ramp. Right now, traffic (destined for downtown) exits at either Seneca or, less likely, Western, and can enter from Columbia or Elliott. Everyone else passes through the Battery Street tunnel and turns around, or gets off waaayy down south near Spokane Street and traverses 1st or 4th Avenues. An Alaskan Way that has signalized connections to most/all east/west named streets, and has direct access to the tunnel, will end up serving a whole lot more traffic than it does now because present-day Alaskan Way terminates at a T-junction with 1st Ave. A widened Alaskan Way won't induce demand in a way that brings more cars downtown, but it will encourage more cars to use Hwy 99 + Alaskan Way, versus Spokane Street Viaduct + 1st or 4th Avenues.

So we're basically in agreement.

[jakeroot]

There is one omission from the tunnel design that is different from the current viaduct: no downtown exits or entrances. This means that cars going to and from the south will need to use Alaskan Way to enter or exit the Hwy 99; essentially, Alaskan Way will become a giant on-/off-ramp. Right now, traffic (destined for downtown) exits at either Seneca or, less likely, Western, and can enter from Columbia or Elliott. Everyone else passes through the Battery Street tunnel and turns around, or gets off waaayy down south near Spokane Street and traverses 1st or 4th Avenues. An Alaskan Way that has signalized connections to most/all east/west named streets, and has direct access to the tunnel, will end up serving a whole lot more traffic than it does now because present-day Alaskan Way terminates at a T-junction with 1st Ave. A widened Alaskan Way won't induce demand in a way that brings more cars downtown, but it will encourage more cars to use Hwy 99 + Alaskan Way, versus Spokane Street Viaduct + 1st or 4th Avenues.

So we're basically in agreement.

Maybe. I haven't made up my mind. Anything that relieves pressure will make it easier for the compressed energy to flow. If future Alaskan Way makes it easier to drive downtown, I have a hard time believing that more people won't switch back to driving (even though my previous comment states the exact opposite ).

Even if we surmise that more cars don't come downtown after all of this waterfront work is finished, Alaskan Way will basically begin to act as though it were an at-grade interstate spur into downtown from the south (like I-180). It will be busy, a lot. Most of the time, I'd bet. In fact, I have no doubt that it will be substantially busier than present-day Alaskan Way, because it serves a much bigger purpose. While we have the opportunity to build ourselves a great waterfront, we really ought to keep the cars downtown in the one-way system, away from the waterfront where walkability should be king (which it won't be if there's a giant 8-lane expressway running right alongside it, simultaneously separating it from downtown).

[cpzilliacus]

Seattle Times: How did we get here? A look back on Seattle's tunnel machine Bertha

Bertha's end could be near.

The world's largest tunnel-boring machine is on schedule to break into daylight this spring after a tumultuous dig under downtown Seattle that's years behind schedule.

The massive drill is part of the state Department of Transportation's multibillion-dollar plan to replace the aging Alaskan Way Viaduct, which runs about two miles along the city's waterfront and could buckle in an earthquake.

We've spotlighted Bertha's technical challenges and successes every step of the way.

Here's a look back on that coverage, leading to what is expected to be the four-lane, $2.1 billion Highway 99 tunnel's opening in 2019.

[Henry]

So what are they going to do with Bertha when she's done? I'm guessing one of two things: Either destroy her or donate her to the Smithsonian.

[nexus73]

So what are they going to do with Bertha when she's done? I'm guessing one of two things: Either destroy her or donate her to the Smithsonian.

Would there be any sense in drilling more tunnels in Seattle?  If so, keep it around for that time!

Rick

[jakeroot]

So what are they going to do with Bertha when she's done? I'm guessing one of two things: Either destroy her or donate her to the Smithsonian.

I suspect she will be scrapped. There simply is no other use for a tunnel boring machine that large. The Sound Transit tunnel boring machines are being re-used because multiple tunnels need digging, but the Alaskan Way tunnel is very much a one-off project.

[kkt]

Yes, scrapped.  They're too big to transport economically.  They aren't built with the expectation of re-use; once they've dug and dug for a couple of years on one project they're pretty much shot.