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Author Topic: Alaskan Way Viaduct Replacement Tunnel  (Read 193009 times)

compdude787

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Re: Alaskan Way Viaduct Replacement Tunnel
« Reply #875 on: December 30, 2020, 02:30:17 AM »

Now I wonder if I-5 will ever get the big dog treatment through downtown Seattle. That road needs at least 6 lanes each way.

God no. We do not need that at all. Not in a million years.
I disagree. It needed it 10 years ago.

I like my wide freeways as much as the next roadgeek, but I recognize that while I-5 may "need" many more lanes through downtown if you just take a surface level look at the traffic backups, there are many other factors at play. I-5 already has 5 lanes per direction to the south, and 4 per direction, plus the express lanes, to the north. The reason for reduced lanes downtown is due to the vast amount of traffic demand exiting downtown, and adding more through lanes would only shift the traffic jams to the edges of downtown (not to mention the complete lack of space for said additional lanes). Increasing capacity by eliminating bottlenecks and poor design choices (looking at you, left exits) would have a greater impact for much less cost and actually has at least some chance of being constructed.

For example, WSDOT is painting a third lane through the northbound bottleneck downtown, which should balance things out in terms of capacity to demand and ease traffic through the area.

Agreed. I-5 is plenty wide already. There are several chokepoints on I-5 through downtown Seattle, including the one mentioned above, as well as the left exit and entrance at 520 as well as Mercer Street. They need to fix those before considering adding more lanes!

jakeroot

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Re: Alaskan Way Viaduct Replacement Tunnel
« Reply #876 on: December 30, 2020, 04:09:23 AM »

Now I wonder if I-5 will ever get the big dog treatment through downtown Seattle. That road needs at least 6 lanes each way.

God no. We do not need that at all. Not in a million years.
I disagree. It needed it 10 years ago.

I like my wide freeways as much as the next roadgeek, but I recognize that while I-5 may "need" many more lanes through downtown if you just take a surface level look at the traffic backups, there are many other factors at play. I-5 already has 5 lanes per direction to the south, and 4 per direction, plus the express lanes, to the north. The reason for reduced lanes downtown is due to the vast amount of traffic demand exiting downtown, and adding more through lanes would only shift the traffic jams to the edges of downtown (not to mention the complete lack of space for said additional lanes). Increasing capacity by eliminating bottlenecks and poor design choices (looking at you, left exits) would have a greater impact for much less cost and actually has at least some chance of being constructed.

For example, WSDOT is painting a third lane through the northbound bottleneck downtown, which should balance things out in terms of capacity to demand and ease traffic through the area.

Agreed. I-5 is plenty wide already. There are several chokepoints on I-5 through downtown Seattle, including the one mentioned above, as well as the left exit and entrance at 520 as well as Mercer Street. They need to fix those before considering adding more lanes!

If they did actually go and fix all of those merge issues (Mercer Weave, 520 Shuffle), given the hundreds of millions that it would cost, I think we'd be hard-pressed to actually want to spend more to add lanes. Especially when you consider the general number of lanes in the city limits overall: we could expand I-5 to five through lanes through Seattle (at a considerable expense), but where are those lanes coming from? Where are they going? Because the Ship Canal Bridge only has four lanes in each direction over it (plus the reversible lanes), and that is not up for replacement anytime soon. I-5 is five lanes south of downtown but only if you count HOV lanes. Five regular lanes would require total reconstruction of the bridge system south of downtown.

The fact is that adding additional lanes to I-5 in a major fashion would require absolutely insane amounts of money. It's not happening, and there's virtually zero chance of it ever happening. The best we can hope for is improved ramp configuration and better city planning.
« Last Edit: December 31, 2020, 05:32:38 PM by jakeroot »
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jakeroot

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Re: Alaskan Way Viaduct Replacement Tunnel
« Reply #877 on: December 30, 2020, 04:11:01 AM »

^^^^^^^^^

Couple of questions. About 30 seconds in, there is an LED Speed Limit sign. Can this be changed based on traffic conditions? Also saw the speed limit in the tunnel is 45 mph.  Is tat fixed or is it also variable?

I think it's designed to change, but I've never seen it as anything other than 45. That limit matches the limit north of the tunnel along Aurora Ave.

I've seen lower speed limits driving through it during afternoon rush hour (back in 2019), so yes, it does change. I think the lowest I saw them go was 30. They can also be used to alert of lane closures and hazards, similar to the other per-lane LED signs in the Seattle area. I actually happened to get pictures of this in action, shown below.







Nice catch!! I've never seen those signs displaying anything other than 45, even when traffic was crawling.

Looks like traffic was ignoring the overhead matrix displays. Did they finally merge when they caught up to whatever incident was blocking the left lane? I'm personally a fan of using the whole road, right up to an incident, so seeing these "lane closed" signs without anything in sight does bother me as it seems to be a waste of lane space.
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stevashe

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Re: Alaskan Way Viaduct Replacement Tunnel
« Reply #878 on: December 31, 2020, 04:34:24 PM »

Nice catch!! I've never seen those signs displaying anything other than 45, even when traffic was crawling.

Looks like traffic was ignoring the overhead matrix displays. Did they finally merge when they caught up to whatever incident was blocking the left lane? I'm personally a fan of using the whole road, right up to an incident, so seeing these "lane closed" signs without anything in sight does bother me as it seems to be a waste of lane space.

If I recall correctly, that red X was the first one, so people were just starting to merge there. I don't think you could see the disable vehicle yet, but it was just out of sight around the bend. A few people did defiantly stay in the lane and race ahead though, only merging when they saw the obstructed lane.
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kkt

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Re: Alaskan Way Viaduct Replacement Tunnel
« Reply #879 on: December 31, 2020, 05:07:14 PM »

Because the Ship Canal Bridge only has four lanes over it, and that is not up for replacement anytime soon. I-5 is five lanes south of downtown but only if you count HOV lanes. Five regular lanes would require total reconstruction of the bridge system south of downtown.

Maybe I didn't understand what you were trying to say.  At the Ship Canal Bridge, I-5 is four lanes each way plus four reversible express lanes.

Northbound I-5 drops down to two lanes past the Seneca Street exit.  Southbound isn't quite as bad.
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jakeroot

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Re: Alaskan Way Viaduct Replacement Tunnel
« Reply #880 on: December 31, 2020, 05:31:57 PM »

Because the Ship Canal Bridge only has four lanes over it, and that is not up for replacement anytime soon. I-5 is five lanes south of downtown but only if you count HOV lanes. Five regular lanes would require total reconstruction of the bridge system south of downtown.

Maybe I didn't understand what you were trying to say.  At the Ship Canal Bridge, I-5 is four lanes each way plus four reversible express lanes.

Northbound I-5 drops down to two lanes past the Seneca Street exit.  Southbound isn't quite as bad.

That's what I meant. I appreciate you clarifying. Anymore than four approach lanes to the bridge is pointless.
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