Wednesday, March 16, 2016

A fix to ease a bottleneck on northbound I-405

I-405 striping changes near the SR 520 Interchange

By Caitlin Morris

The problem—congestion on I-405 at SR 520
If you drive northbound on I-405 often, chances are you’ve run into traffic at the northbound I-405/SR 520 interchange, where drivers from both highways converge and traffic can back up. We’ve heard about it from drivers, and we’ve seen it ourselves. You’re frustrated and we want to fix it.

We’ve been looking for opportunities to improve traffic flow at this critical interchange. With the express toll lanes now open, we’ve had the chance to monitor traffic patterns and create plans that respond to drivers’ choices.

What we’ve seen
Many drivers entering the express toll lanes at SR 520 are coming from downtown Bellevue. While Northeast 6th Street provides a direct access into the express toll lanes from downtown, we are seeing that people are not always choosing this new option and instead they’re using the SR 520 access from Northeast 4th Street and Northeast 8th Street ramps. But as the name indicates, the SR 520 access point occurs right near the on-ramp from SR 520, meaning that a lot of cars are converging at the same point on the highway, creating the bottleneck.

Our goal is to open up this chokepoint, allowing more space for cars to flow. To do that, we need to get cars into the express toll lanes earlier and give vehicles from SR 520 more time and room to safely and easily merge onto the highway.

How we’ll improve access into the express toll lanes
Our plan to improve traffic flow has two components. First, crews will extend the SR 520 to northbound I-405 on-ramp by a half mile to give drivers more room and time to merge into the I-405 general purpose lanes. Second, crews will triple the length of the express toll lane access point at SR 520, extending it southward, allowing drivers from downtown Bellevue earlier access into the express toll lanes.

That means the access point will change from a weave lane to a skip stripe type of access. As you can see in the before and after diagrams, a weave lane has striping that acts like a cushion, allowing drivers space to merge in and out of the express toll lanes without holding up the drivers behind them.

A skip stripe is made of simple dashed lines that indicate it’s OK to enter and exit the express toll lanes. A longer skip stripe provides more access and more opportunity to find a gap in traffic when moving from slower to faster speeds.

These changes will allow drivers to access the express toll lanes sooner from Northeast 4th Street and Northeast 8th Street in downtown Bellevue. By the time express toll lane users reach SR 520, they’ll be out of the general purpose lanes, providing more space for the drivers entering I-405 from SR 520.

What to expect
Crews will make these changes Friday, March 18 through the morning of Sunday, March 20 with the following closures:

From 8:30 p.m. Friday, March 18 to 9 a.m. Saturday, March 19
  • Up to four right lanes of northbound I-405 between Northeast 8th Street to Northeast 70th Place
  • The SR 520 on-ramp to northbound I-405
  • The Southeast and Northeast 8th Street to northbound I-405 on-ramps
From 9 p.m. Saturday, March 19 to 5 a.m. Sunday, March 20
  • Up to three left lanes of northbound I-405 between Northeast 8th Street to Northeast 70th Place
This work is weather dependent and requires two nights of favorable weather conditions to complete the lane striping. Signed detours will be in place.

Keep in mind that it may take drivers awhile to get used to the new striping. So be alert when you’re driving through the area as the road will look a little different. And remember, the bottleneck won’t disappear overnight; drivers will need time to adjust to the new configuration.

In case you love to access the express toll lanes via the Northeast 6th Street Direct Access ramp, don’t worry, the ramp won’t be affected by this work.

Keep talking!
We’ve made changes along I-405 based on driver feedback and we’re looking forward to continuing the trend. So drop us a line. What other changes might help traffic flow? We’d love to continue the conversation.


Matt Johnson said...

So what happens with regard to traffic coming from SR520 trying to cross over three lanes of traffic to get into the toll lanes?

Joe Gforce said...

To get to 405 N from SR520

A) Be sure your insurance is up to date
B) Repeat the following

Forgive us our trespasses,
as we forgive those who trespass against us;
and lead us into Bothell,
and deliver us from WSDOT
C) Send the sideswipe bill to WSDOT

Mark Beales said...

The HOV exit lanes north of Beardsley are too far north to allow drivers in the HOV lanes a way to get into the far right lane exiting to 527. The right lane is backed up almost to the on ramp from Beardsley and it's bumper to bumper. The way it is now, one exiting the HOV lane literally has to almost come to a complete stop waiting for a break to get into the far right lane. Begin the exit lane at the Beardsley overpass to allow drivers who want to exit on 527 enough time to get into the far right lane.

G Swi said...

That's funny, Joe. Humor appreciated.
On a serious note, it's a bad plan. The problem as it is now is the 520 to 405 north ramps coming from both east and west merge into a single lane going up hill. You crawl until you get to the point you are allowed to enter the traffic stream.

And the DOT thinks making that point even further up the ramp is a good idea? For who? Anyone but those of us coming from 520, I guess. What a nightmare. It takes so long to get on 405 at that one bottleneck it might just save time to get off 520 at 124th and work backward to the 6th St onramp.

What's wrong with you folks at the DOT that you can't diagnose a problem? It's not getting across to the toll lanes, it's getting into the 405 traffic stream in the first place. By that time traffic is moving so slowly on 405 changing lanes isn't that hard. The problem is you waste 30 minutes going that one mile to get on 405 before you can get to the toll lanes.

I believe the solution will make traffic back up further on 520 as the ramps to 405 north move even slower.

Vince R said...

It will be interesting to see if this works. From the diagram, I can see people trying to jump into the ETL from the 520 merge lane and stopping as they weave across traffic to try and get in. I think it needs to be super clear that you cannot enter the ETL from the 520-405 interchange.

What is needed, and unfortunately its dang expense to do, is a HOV/ETL flyover, similar to how it used to work on 405 S to 90 W, where the need to weave across all those lanes of traffic is completely eliminated.

Besides the cost to implement such an improvement, there are two other issues:
1. The impact the construction would have now that the traffic is so bad.
2. It does not appear that there is not enough land set aside (or set back) to add in the flyover.

At this point, after GTG went in, the 520-405 interchange is so bad, trying something else needs to be done. And we need to keep trying new things until the problem is significantly less. The 405N to 520E is still a bit of a pain, but it is better than it used to be. We just havent invested in a similar change on the reverse side of the interchange process.

oneeyedelf1 said...

You made it longer, yet put a giant white line that you aren't supposed to cross, how is that going to help?

After the white line ends there is no way to get all the way to the HOT Lanes.

A huge problem with 520 to 405 is the massive build up of both 405 south and north on 520 west bound, the 405 south backs up so far that it blocks 405 north, meaning now there are people that try to cut in after 405 north and its just well crazy, there needs to be separate lanes for 405 south and 405 north much further back or entrances on different sides of the highway, also sharing the lane with HOV sucks. PLEASE PLEASE fix 520 west into 405.

Jeff Day said...

Matt, check out the drawings. You have more room/time to move over to the left now.

Jeff Day said...

Matt, the drawings show there merge lane is longer and provides more time for drivers coming from 520 to move to the left. Still not ideal but clearly an improvement.

Cu Bong said...

WSDOT should change the same on Exit/entry on SOUTH 405 at SR-520 as well.
you should get rid of wasting weave lane and using simple dash-lines instead.
WSDOT insist that this section isn't a problem. we are frustrating every morning to see all the drivers driving in a very narrow space while ETLs+ weave+shoulder taking up 2/ 3 or the freeway width . Get rid of the weave lane and use it to making exit only lane longer to SR-520 .\
Before I posted the comments about these section, WSDOT insist that we need the weave lanes for safety , now you removed on the north bound you SHOULD do the same on southbound, giving back spaces for GPLs...
we are very frustrating every morning to see these non-sense lanes designed for the southbound

WSDOT said...

Vince R et al, the I-405 Master Plan does have plans for direct connector ramps the SR 520 HOVs to the I-405 the express toll lane system. Unfortunately, those projects are currently unfunded.

In the meantime, drivers on Saturday morning can expect the express toll lane access point to start about 1,000 feet earlier and no longer have the weave lane. The new access point will be a skip stripe access similar to the access in downtown Kirkland. Drivers from SR 520 will notice that the northbound I-405 on-ramp will extend another half mile north. Sunday morning, drivers will notice that the express toll lane will start much farther south and be three times longer.

We are observing how commuters are utilizing the express toll lanes, and making adjustments accordingly. See more information on future improvements here:

Unknown said...

1. There needs to be a way to get into the ETL when merging from the 520W to 405N. The entire congestion is clustered in that area, and not providing an entry to the ETL pretty much defeats the point since by the time you get to an access point the congestion has cleared up.

2. The merge lane from 520W to 405N needs to be skip striped, not solid line. This allows merging traffic to filter in opportunistically instead of being forced to find an opening at a specific point, forcing both merging and highway traffic to slow to make things line up at that point.

Travis Pahl said...

how about striping changes to fix the congestion at I90E to I405S? The ramp between the two has plenty of room to be 2 lanes the whole way but instead the lines force everyone down to one, only to open immediately back to 2. make it 2 lanes all the way through and make the right lane a coal creek pkwy exit only lane. That would get more people through the choke point and seperate people better once they get on I405.

Brian Peterson said...

Yes this! It needs to be more than tripled. I didn't even know it was possible to enter hoc from 520 today given the traffic

Brian Peterson said...

This x 100. I didn't even know it was possible to enter hoc from 520 given the traffic. It needs to be more than tripled.

Vince R said...

@Travis I have come through that area with a trailer and I am not entirely sure how much margin of error would be available. Imagine the turn radius with a 40' trailer in tow... then imagine the rude 'I am going to weave in traffic and slam on my brakes' person that does that in front of a truck. There are areas where we have 'fit' lanes in by removing shoulders and making the lanes narrower. Its pretty challenging driving when your tires are only given 8 to 12 inches of clearance on each side of the lane.

Vince R said...

@oneeyedelf So I could be wrong, but you want to promote traffic that enters the highway, at rush hour, that immediately jumps 4 lanes across traffic so they can use the ETLs?

I would argue that this should not be allowed and the next open area to enter the ETLs should be around a mile up. Here is my reasoning:

1. Weavers, those that actively jump across lanes, most often negatively impact traffic flow. They don't see the wake of brake lights they create behind them and this is a domino effect at rush hour.

2. Weaving traffic is less safe. Its not just me that thinks that. Statics show its true and prior to GTG, WSDOT had campaigns to eliminate weave patterns to improve safety. (no idea what happened with that but you don't hear much about it now). Oh, and it's not just WSDOT that thinks weaving is less safe (although you wouldn't know it from GTG), the feds don't think its safe either.

3. The shorter the weave pattern distance, the higher the risk of accident. Again, stats show this one and its recognized at a fed level to be a bad practice.

4. Anything that can negatively impact traffic flow (IE lead to traffic jams being created or getting worse) and reduces safety on our roads is considered a bad design. That one is just part of the definition of bad design... no logic or anything crazy needed there.

So when I look at this proposal, as much as this idea might not be popular, I don't think that traffic should be able to immediately enter the ETLs from the 520/405 interchange and that until an entrance can be created/funded to address this, and so long as it is an operational requirement to enter/exit at specific points to properly account for tolling, I don't think it is a good idea.

The words from one of the public safety commercials come to mind:
"How many fatality accidents are acceptable on our roads?"

Everyone thinks it ok to have some... until you ask this question...
"Would it be ok if someone you cared for died in a traffic accident?"

So long as someone else is negatively affected people think its ok... but once they are affected its not. Remember, most people are not using the ETLs... why should they be affected by the few that do. Why should their lives be put at risk so little Sally can get to soccer practice sooner.

I was almost been hit by someone carelessly doing the 'GTG weave' in the last week... driving their 8 cylinder land yacht/family killer and pretty much not looking to see if anyone else might be using 'their' road. Unfortunately this behavior is not uncommon and seems more prevalent since GTG went in. We had to slam on our brake to avoid the collision and they never even noticed we were there. Probably too busy chatting on their phone.

Vince R said...

I should have posted references on the weaving stats... so here are a few:

Safety aspects of freeway weaving sections
"... the total number of lane shifts required by drivers in weaving sections affect both weaving and non-weaving speeds..."

"...Studying accident experiences among weaving sections, from 700 weaving sections in
20 states based on data gathered in the early 1960s, Cirillo (1970) determined that shorter acceleration and deceleration lanes exhibited higher accident rates, for all percentages of merging or diverging traffic. The effect of increasing the length of acceleration lanes appears to be substantial when the percent of merging traffic is greater than 6%, and below the 6% range improvement was speculative and probably not cost beneficial. ..."

"... A recent study sponsored by The Washington State Department of Transportation (Glad,
2001) studied accidents occurring in a particular weaving area by collision type and severity from 1994 to 1996, finding that the predominant accident types during peak hours periods were rear end collisions occurring at lower speeds upstream of the weaving section, while during off-peak hours, the incidence of sideswipe as well as rear end collisions increased considerably ..."

(btw... this is the exact condition we have created with the new design )

"... Also, accidents within weaving sections are more likely to involve citations other than speeding, because sideswipes are more likely to be attributed to violations such as failure to yield or other dangerous driving. ..."

Effects of Weaving on Traffic Flow

"Because vehicles typically accelerate/decelerate when weaving, the capacity of a freeway network is reduced. Not only does weaving impact effective capacity, it affects the safety of motorists. Due to safety concerns, attention will be given to weaving zones where there is a high speed differential between weaving lanes."

This statement indicates that creating weaving patterns, like GTG does on 405, it unsafe...

Relationship between Weaving Length and Traffic Safety in Road Interchanges

"Weaving areas in road interchanges are dynamic areas, where vehicles change lanes frequently to complete merging and diverging operations in a short distance. As a result, traffic flow is rather unpredictable and volatile, with negative impact on the safety and efficiency of the entire interchange"

Weave Distance
"More weave distance is needed when traffic volume OR traffic speed is high. "

"ODOT is concerned about driver safety when weave distance is too short near major intersections, signalized intersections and interchange ramps. Weaving creates conflicts when weaving vehicles slow the speed of through traffic and block travel lanes while maneuvering"

Weave Analysis and Performance: The Washington State Case Study
"The accident rates were substantially higher for acceleration lanes than for deceleration lanes. Cirillo found that the shorter the length of the lane the higher the accident rate regardless of the percentage of merging or diverging traffic."

Helena said...

They need to get rid of the extortion lanes and then we will see real improvements in traffic congestion. When the extortion lanes when in traffic became much much worse. This is why WSDOT is acting like they are doing us a favor by making the extortion lanes free after hours and weekends. This still does not do anything for everyone suffering during the day. This is not over. We will continue to fight against the biggest mistake in transportation history and we will win. No one wants these extortion toll lanes. Real Lanes for Real People!

dude463.waze said...

My question is pretty simple. Are you intending drivers from the SR-520 to north bound I-450 be able to actually merge all the way to the express toll lanes? You've said that you don't let the Express Lane drivers from I-90 westbound use the Rainier Ave exits (signed). Isn't this about the same distance?

Travis Pahl said...

@vince: Take a look again at this exchange. There is a good 15-20 feet of unused shoulder.

Vince R said...

Somewhere in the research material funded by WSDOT I recall reading a minimal suggested distance for merge/weaves... something like 750 feet (but it might have been meters), provided there were no mitigating factors... where anything less than that was a reduction of safety.

So looking at the diagram of the changes, and knowing that we are talking about a 5 lane weave, the minimal distance should be something like (number of lanes we think people will be weaving) X (minimal safe distance) OR (5) X (750) OR 3750 feet.

Now there are mitigating factors that were specifically identified in the research as causing higher incident rates (which are not limited to just accidents):
* high speed differentials between weaving lanes
* inability to accelerate

As GTG is designed, there is a speed differential between the ETL and the GPL which, by research funded by WSDOT clearly identifies that as a safety issue. When entering the ETL from the GPL, the weaver will be going slower than the traffic they are weaving into. When exiting the ETL, weaver will be going faster than the traffic they are weaving into.

Second, this area of the highway is at an incline, impacting the ability for some vehicles to accelerate as they would on a flat roadway. This is another form of the same issue listed above.

For these reasons, if WSDOT designed the GTG system such that it intended 520 traffic to weave into the GTG lanes with anything less than 3750 feet, they would be knowingly putting lives at higher risk.

I would assume that for our sakes, they haven't done that. I have not yet seen the new design, but I do not want to see people injured if the appropriate safety measures haven't been followed. The research material made it clear that the impact of a poorly designed weaves create incidents upstream of the weave area, as well as down-stream.

It would really peeve me off if the money collected from the tolls ended up used in some kind of wrongful death lawsuit because the WSDOT didn't follow the guidelines from research that they funded.

All that said, it is super hard to tell if the drawings were to scale and if the intent was that people entering 405 from 520 were to weave all the way across the highway in what appears to be about 50 foot of road (or 5 car widths).

Vince R said...

As a side note, and this is entirely my opinion but I would love to see any information about it either way, as we have designed GTG, we do not have a simple weave as was outlines and studied in most of the research material I listed above. We have a double weave, were people both enter and exit in the same locations. In my opinion, this is a mitigating factor that should require either:

A) Separate 'entrance' and 'exit' weave locations


B) longer weave distances than those that were prescribed in the research from about 14 years ago, which I seem to remember being 750 feet (or meters, I can't recall but I think it was feet)

In my opinion, option 'A' would probably be safer, but again, I can't back that up with anything I have read.

This is one of those cases were it just doesn't look right, so I am using the same approach for it as was used in determining if somethign was obscene in the 'Jacobellis V. Ohio' case...

"I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description..., and perhaps I could never succeed in intelligibly doing so. But I know it when I see it

When I look at the new approach, it just seems to scream safety risk to all commuters, upstream or in the immediate area, if people are intended to weave into ETLs directly from 520.

I would love for WSDOT to say otherwise, or to point me to some research material that shows this is safe.

WSDOT said...

@oneeyedelf1 – The changes will allow drivers to access the ETLs sooner, and changes in striping give drivers more space to merge in and out of the ETLs without holding up other drivers. While these are big improvements, we are always taking feedback into consideration to make the system work for everyone.

Helena said...

These changes don't do anything in regards to the mess that everyone is facing every day with the extortion lanes. What good does nights and weekends really do when the majority of users still suffer every day. How dumb does WSDOT think the public is? We would all be better off if the extortion lanes were suspended ASAP. The new and improved configuration would be 4 general purpose lanes and 1 HOV lane. We are not finished and we still have more work to do. We will get rid of the extortion lanes. We will win the fight!!!

Vince R said...


It might not seem like it, but making the ETLs work like the old HOVs is a step forward. It actually reduces the percentage of money collected that is lost to operational overhead and helps improve congestion on weekends.

It doesn't address the issues created by GTG during peak hours but its a start.

WSDOT said...

@dude463.waze - We do intend for drivers entering northbound I-405 from SR 520 to be able to use the express toll lanes. Drivers entering I-405 from the express toll lane access point north of SR 520 have nearly a mile (at least 4,800 feet) to move over to the express toll lanes. This is because we allow 800-1,000 feet of room per lane change needed to enter the system. By contrast, drivers have an estimated 1,200 feet to cross three lanes of traffic on the westbound I-90 Express Lane to get to Rainier Avenue South.

Vince R said...


The drawing at the top of the page depicts something that is not to scale or not quite what your are saying. It appears that the entrance to the ETLs is almost directly across from the merge from 520 to 405. Is that just an issue in the drawing?

Based on the data that I read, a mile is just about right. What has the impact of this change been?

WSDOT said...

@Vince R, I can see how that diagram is a little difficult to read in this circumstance. The scale is more or less accurate, but the line dividing the SR 520 on-ramp and the right-hand general purpose lane of northbound I-405 is different than what you would see on the road. On the road, that line is actually a dashed line, indicating to drivers that it’s OK to begin to merge left. That mile that drivers have to merge over to the express toll lanes begins just after the southernmost point of the SR 520 access point. I hope this helps make the diagram a little easier to use. Apologies for the confusion.

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