by Bart Treece

by Mike Allende

Concrete sealing part of the new expansion joint

The concrete needs about 12 hours to cure but workers will be monitoring it this afternoon. The concrete needs to reach a strength of 2,500 psi (pounds per square inch) for traffic to go over it. Whenever that happens, we’ll be switching the work zone to the other side of the highway to work on the other half of the joints. That is scheduled to happen around 9 p.m. Monday morning drivers will see traffic moving through the work zone in the Phase 2 configuration.

Phase 2 - Monday - Friday morning

By Mike Allende

By now, hopefully you’ve heard that westbound Interstate 90 will be reduced to one lane at Bellevue Way Southeast from 9:30 p.m. Friday, July 18 until 5 a.m. Friday, July 25. That’s 24-hours-a-day for a week, and yes, it’s going to be messy.

During that time, contractor crews are going to be replacing two huge, old expansion joints embedded deep in the roadway near Mercer Island. They’re 33-years-old and despite repairs over the years, they are at the end of their useful life.

We don’t make decisions to do these kind of closures lightly, and a lot of thought and discussion went into it. There’s never a good time to close lanes on major highways. In the end, doing a few weekend closures like we did for our I-5 expansion joint replacement just wouldn’t work this time.

Construction details
These expansion joints are massive, much bigger than those on I-5. Each of the 33-year-old joints are 92-feet long and weigh almost 29 tons. They’re embedded into 11-inch-thick concrete. Chipping out the concrete, replacing the joints, pouring new concrete and letting that concrete cure for a minimum of 12 hours would take longer than a typical weekend-long closure allows. Once in place, between 24 – 30 hours of welding is needed to connect both sides of the new joints.

Keeping traffic moving
No two-ways about this, we’re going to need your help. Knowing what to expect and staying informed is something everyone can do. For an idea of what this closure will look like, we put together this animation showing what is closed and how cars will move through the closure.

As the animation shows, besides the three lanes of I-90, we’ll also have some ramp closures. Take a look and get an idea of how to move through the closure if you end up having to go that way.

Stage 1

Stage 2

If you don’t plan ahead, your typical commute could last an hour or more. The best advice is to avoid using westbound I-90 during the closure. With a big Sounders match and the Mariners in town, along with work and other trips, we know that’s not easy. Taking an alternate route will help, but still add extra time to your trip because other routes will be affected with folks doing the same thing. If you can telework, or even take a vacation, this would be the week to do it.

When we had two lanes closed on westbound I-90 floating bridge in July 2009, we saw up to 7-mile backups, but we had the express lanes to help. On this closure we do not. Congestion could be much worse this time around.

To keep delays from really getting horrible, we need at least 60 percent of drivers to adjust their plans. We recognize that’s a lot to ask, but every person who can change their plans helps.

The graph below shows that normal peak travel times on westbound I-90 in the closure area are up to 15 minutes in the morning, up to 30 in the afternoon. If we get a 60 percent diversion during the closure, we still expect morning travel times to be 45 minutes to 1 hour, and a little longer in the afternoon. So if there's any way for to you avoid the area that week, do it.


We wouldn’t do this closure if we didn’t have to but it’s vital to maintaining our infrastructure and avoiding emergency closures that would lead to having to replace the expansion joints anyway.

Tolls on SR 520
Folks have asked us about tolls on SR 520 during construction on I-90. SR 520 is just one route from the Eastside to Seattle. The Transportation Commission sets toll rates and exemptions and there are none for this project or other construction closures. Drivers can set up a short-term account and can save $.50 on the pay-by-mail toll rate.

Aging infrastructure
This is a safety and mobility issue. We’ve had several temporary fixes over the years, and these expansion joints simply need to be replaced before they break.  If we do nothing, this could happen during a busy commute and tie up traffic for a long time. Vehicles could be damaged and lanes of traffic closed for an indefinite amount of time. As you can imagine, you can’t just go to the store to buy a replacement expansion joint. These are custom made for the bridge, and it takes between six to nine months to fabricate.

New expansion joints to be installed

It’s not going to be easy, but hopefully with some planning and adjustments, many of you may be able to avoid the congestion that inevitably happens with a major closure like this. With many of our roads being 30 to 60 years old, this is a step we need to take to ensure they can meet the demands of day to day traffic.

Learn more about the I-90 closure on the project website.

by Guest blogger Mike Allende

Hockey is a winter sport and WSDOT is getting in on the puck action. Well, kind of. While it doesn’t involve goalies, slap shots or penalty boxes, this action may end up helping traffic move more efficiently.

Soon we’ll be giving Sensys Puck road sensors their first Seattle-area tryout when we install them on northbound I-5 near Northgate. It’s a test project pitting the youthful technology of these wireless sensors against the veteran savvy of existing loop detectors embedded in the roadway in a heated matchup to see which performs best in gathering traffic and vehicle information.



Loop detectors only work with good pavement, and funding for pavement preservation is looking grim. We still need to have reliable traffic information, so as an alternative, the plucky pucks may be the answer.
The pucks are compact and solid, just 3 inches tall and 3 inches in diameter, but don’t let their size fool you. There’s plenty of power and versatility packed in those little bodies and they hold up well under pressure, whether it’s a semi-truck or heavy rain.

What can these little guys do? Plenty. They count every car as it goes by, measuring speed, lane occupancy, gaps between vehicles, direction of travel and even vehicle length. This information is valuable in evaluating traffic flow and signal control, and letting drivers know if a road is congested or not on our flow map. That’s some MVP ability.

Inductive loops have similar skills but require pavement that is in good shape in order to work well. Pucks are also easier to handle than the gangly and awkward loops. That means they can get in position quicker, usually just 10 to 15 minutes per puck, leading to a much shorter disruption of traffic. Two loops, on the other hand, take about two hours to install.



To prepare for the puck’s debut, crews bore a circular hole in the pavement, about 4 inches wide and 4 inches deep. We want to put the puck in the best position to be successful, so crews level the holes so that each sensor gets an accurate reading.



After the pucks are in position, they're well protected with a strong epoxy. These guys are valuable and they need to be taken care of. They look sharp and impressive in their black uniforms, but at the same time aren't distracting. They'll fit right in.



The pucks aren’t going to be on their own, though. They team with a local controller, which receives transmissions and crunches data from each individual sensor. The controller can give an overall report about the presence of vehicles, average number of vehicles at any time, average speeds and lane occupancy, among other information. That’s some great teamwork! Loops also work in tandem but have to be hard-wired to a controller device, meaning there are only particular areas they can work without incurring a huge cost.


The pucks often make their appearance overnight to little fanfare, and can even be installed using a brief traffic slowdown rather than lane closures, unlike the loop sensors. They are run by battery and expect to have a long 10-year career. They’re also healthy, and unless the battery dies or there’s an epoxy failure, there shouldn’t be any other maintenance necessary. If maintenance is needed, the pucks can easily be popped out of the pavement, minimizing concrete damage. The health of loops is more questionable, as maintenance is a big issue with these guys. Some loops hold up well over time, others have to retire after 2 or 3 years. Maintenance involves digging up the concrete, dealing with the loop, and replacing the concrete, a much more invasive process. These are huge factors as pavement preservation is vital with increasing traffic. The less the ground has to be dug up, the longer it will last.

So who’s it going to be, the grizzled veteran or the intriguing rookie? The Northgate project costs about $20,000 while a comparable setup with the loops would be about $15,000. The signing bonus is higher for the pucks but add in the costs of maintenance down the road and the potential traffic disruptions and the up-front cost may be worth it. Clearly there are pluses and minuses with both, so the result of this tryout is going to be interesting and exciting to watch!

by guest blogger Jamie Holter

Each day, our traffic engineers monitor traffic through the 440 cameras perched high above Puget Sound roadways. They look for collisions, disabled vehicles, dangerous litter (like bumpers or hubcaps) that could cause collisions or other problems. They also watch traffic flow to determine when to activate systems like Smarter Highways on I-90 (we just activated these signs this week).

Well, it was during a routine traffic check on I-90 when they found Mother Goose and her five goslings booking down the shoulder of I-90. Washington State Patrol spotted them too and herded (herded? guided?) them off at the next exit. Not only do we want them to make it through spring, but we also want to make sure they don’t wander in front of your car. Can you imagine how bad you’d feel if you hit one? Or the mess it would cause if you swerved to try not to hit it?