In another chapter of “while you were sleeping,” we tell the story of the overnight work that recently went into creating the concrete deck for the northbound side of the Interstate 17 bridge that’s under construction above Central Avenue in Phoenix.

For ADOT, the I-17 bridge over Central Avenue had reached the end of its service life. Makes sense, since it originally opened to traffic back in 1962.  Over the past year the old bridge has been demolished in phases and a new bridge has taken shape south of the downtown area.

One of the last major moves was the concrete pour for the new northbound bridge deck. It takes a number of loads of concrete shipped via trucks. And as you can see in this ADOT I-17/Central Ave Bridge Video, an extended boom pump system delivered the concrete from street level on Central Avenue up to the bridge deck. It reminds me of a series of fire hoses that pump concrete instead of water.

Crew members then poured the concrete into the network of steel rebar that provides strength for the bridge deck. Specialized equipment, including a Bidwell pavement roller, is then used to spread and smooth the concrete pavement that drivers will be traveling on within a matter of months.

For this particular operation, 545 cubic yards of concrete were poured for this span in just a matter of hours.

So let’s review the project’s advances since work started in May 2020. Project phases included demolishing and reconstructing the southbound side of the steel-girder bridge. I-17 traffic, which had temporarily been sharing the old northbound side of the bridge, was then shifted to the new southbound span earlier this year. In turn, that allowed the same type of demolition and reconstruction work to take place for the new northbound side of the bridge.

Now it’s on to the last stages of work to finish the entire bridge so I-17 traffic can once again travel through the area with three lanes in each direction. The new structure will be wider to accommodate regional plans for additional lanes along I-17 when future funding is available. Increased clearance below along Central Avenue will provide more room for commercial trucks as well as Valley Metro’s future South Central Avenue light-rail line.

The $13.5 million project has been funded in part by Proposition 400, a dedicated sales tax approved by Maricopa County voters in 2004.

Today’s Throwback Thursday entry goes back to 1971. Flip Wilson is on your TV, the price of peanut butter is 59 cents, and Sunset Point is looking mighty inviting.

Yes, here’s a look at Interstate 17’s favorite rest area one half century ago. We can spot a Volkswagen Bus, a pickup with a pretty impressive camper shell, and perhaps a Buick Skylark towing one of those fancy silver Airstream trailers.

Fifty years later, Sunset Point remains a popular pit stop for folks traveling up and down I-17. Except now there are a few more vending machines and a lot more parking. Those baby trees in the foreground are undoubtedly nearly grown now, too.

Not much beats the breathtaking views Sunset Point offers. Especially around dusk, when you can take in a little thing called…the sunset.

The highway will definitely look different in the next few years. Interstate 17 is about to embark on an ambitious widening project beginning in 2022, bringing one additional lane in each direction and two flex lanes to the stretch between Anthem and Sunset Point by late 2025.

When it’s halftime in a football game, the teams can use the break to go over strategy for the second half action. But on ADOT’s project to reconstruct the Interstate 17 bridge over Central Avenue, crews didn’t get much of a break before their own second half got underway.

Of course, the strategy was already known. The project team is using “construction in stages” to build the new steel-girder freeway bridge, which will be wider and provide additional clearance for Central Avenue traffic traveling under it. 

The project’s “first half” included a temporary switch of all I-17 traffic onto the existing northbound side of the bridge so crews could tear down the southbound half and build a new span in its place. That work wrapped up in February, allowing crews to use the weekend of Feb. 20-21 to switch freeway traffic to that new southbound span (with two lanes in each direction).

Just one week later (this past weekend of Feb. 27-28), it was time to demolish the old northbound structure. That feat was accomplished with heavy equipment that pounded away and pulled at the girders, the concrete and other material in time to reopen Central Avenue for Monday morning travel.

Now the project team will start the march toward the goal line. They will build the new northbound half of the I-17 bridge south of the downtown Phoenix area. Completion is scheduled for this fall. At that time northbound traffic will be switched to its rightful place with more room to operate.

The I-17 bridge will be wider to accommodate regional plans to add more lanes in the future, including auxiliary lanes (also known as merge lanes) between interchanges along the freeway in that area, including Seventh Street and Seventh Avenue.

The improved bridge also will provide more clearance for Central Avenue, not just for larger commercial trucks but also for Valley Metro’s light rail line that also will be passing under I-17.

So I’ll raise my sports drink bottle to the crews on the I-17 bridge project and wish them good luck in the second half. Here’s hoping they give us a game winning drive. Pardon the pun.

You’re not alone if you’ve said, “I can’t wait for this year to be over.” Despite the challenges and disappointments of 2020, there are improvements along Phoenix-area freeways that were accomplished during the year by ADOT’s planners, designers, engineers, contractors and field personnel.

Among the largest steps forward with work to improve highway safety and the movement of today’s and future traffic was completion of the $72 million widening of Loop 101 (Price Freeway) in the area from Baseline Road, south of US 60, down to the Loop 202 Santan Freeway in Chandler. Crews completed the addition of a new lane in each direction, along with other improvements, in August. 

This particular project was moved up in regional transportation plans in order for the added traffic capacity to be in place before the upcoming I-10 Broadway Curve widening project stretching from the Loop 202 interchange in Chandler to the I-17 “Split” near Phoenix Sky Harbor International Airport. That’s because Loop 101 will serve as an important alternate route when I-10 construction closures are needed.

ADOT also completed the reconstruction of the neighboring I-17 interchanges at Happy Valley and Pinnacle Peak roads in north Phoenix. You may not live in that area and haven’t had a reason to check out the significant upgrades at both interchanges, which are just a mile apart along the Black Canyon Freeway. The $50 million project was completed in early December, although many of the improvements were in place earlier in the fall. The most notable change was construction of the state’s first major diverging diamond interchange at Happy Valley Road (smaller diverging diamonds also are in place along Loop 202 South Mountain Freeway). 

The diverging diamond design, which has grown in popularity across the U.S. for safety and traffic flow benefits, uses intersections and traffic signals to allow drivers to cross to the left side of the bridge over I-17 and thus make direct left turns to the freeway on-ramps without crossing in front of opposing traffic. The reduction in such “conflict points” is a primary safety improvement. 

Not to be overlooked is the expansion of the interchange at Pinnacle Peak Road, where drivers now have more lanes to cross over I-17 or make left turns. That’s already helping with the movement of rush hour traffic. Oh, and I-17 was also widened by a lane in each direction between the two improved interchanges.

Another project in our 2020 spotlight didn’t involve widening a freeway, although we wouldn’t blame some drivers if they thought that took place. It was actually an I-10 project completed in the spring that primarily focused on adjusting lane stripes and signs to create more traffic capacity in the area near the Loop 101 (Agua Fria Freeway) interchange in the West Valley. Along eastbound I-10, the changes provided two lanes, instead of just one, for traffic approaching the ramp to northbound Loop 101. The move reduced sudden lane changes and collisions in the area by increasing the amount of room for drivers to work with. Traffic flow also was improved along westbound I-10 with the extension of a right lane carrying vehicles through the Loop 101 interchange. The safety project was done in partnership with the Arizona Department of Public Safety and Maricopa Association of Governments, the Valley’s regional planning agency.

So it’s on to 2021 and other improvement projects, including completion of the Loop 101 (Pima Freeway) widening between I-17 and Pima Road/Princess Drive in the north Valley. We’ll keep you posted on what’s in store. Make it a safe New Year!

As part of ADOT’s recent major project along Interstate 17 in north Phoenix, the reconstruction of the bridge and traffic interchange at Pinnacle Peak Road often took a backseat to the rebuilding also taking place at the busier, nearby interchange at Happy Valley Road.

After all, the I-17/Happy Valley Road interchange received more attention because it was reconstructed as a diverging diamond with new – and different for Arizona – lane configurations and traffic signal setups. 

But enough about Happy Valley Road. We’re here to sing the praises of the new and improved Pinnacle Peak interchange. What a difference a couple of years and hard work can make.

As you can see in the video to the right, the Pinnacle Peak Road interchange now features a much wider bridge crossing over I-17. The old, more narrow bridge was demolished as part of the $50 million project that delivered the upgraded interchanges at Pinnacle Peak and....that other interchange a mile to the north.

Before this project, traffic on Pinnacle Peak Road often backed up approaching I-17, especially in the westbound direction during rush hour. Drivers had to wait in fewer lanes for traffic signals to change.

Now, there are left turn bays with two lanes for traffic entering I-17. That means more “storage capacity” for traffic making those left turns. The I-17 on- and off-ramps at the Pinnacle Peak interchange also were reconstructed with more lanes that provide drivers with improved options at the interchange. The traffic signals are all new and the interchange is much more aesthetically pleasing with individual red paver blocks used to fill the raised median islands.

The modernized, larger Pinnacle Peak Road interchange along I-17 is now in place to efficiently handle today’s traffic as well as traffic in the area for decades to come. We just want to let the new bridge and other improvements at Pinnacle Peak get a little time in the spotlight.

The reconstruction project was funded in part by Proposition 400, a dedicated sales tax approved by Maricopa County voters in 2004.

It is an operation that requires planning, steady hands and a focus on safety. Oh, and let’s throw in another word: measuring. We’re talking about the recent placement of more than 20 steel girders at Interstate 17 and Central Avenue in Phoenix, where the first half of ADOT’s reconstruction of the old freeway bridge continues to advance.

As you can see in our accompanying group of ADOT photos, these are large and heavy girders. Project crews worked earlier in November to lift them into place with cranes, followed by the important work to safely secure them with bracing.

To be a bit more descriptive, these are Continuous Welded Steel Plate Girders. Each of them is 80 to 88 feet long and each tops the scales at between 12 and 15 tons.

For this part of the I-17 bridge project at Central Avenue south of downtown, three girder sections were placed end-to-end in seven rows, also known as girder lines. They will provide the support for what will be the southbound lanes of the freeway when all is said and done in 2021.

These girders are now secured with steel plates that are installed every 16 feet between the side-by-side girder lines. And before you bolt from reading this, give some thought to how many bolts are used in this whole process. Don’t go “nuts” when you learn the answer is more than 6,500 bolts for the entire new structure. It’s all about strength, security and safety.

The focus of this $13.5 million project so far has been on rebuilding the southbound side of the bridge over Central Avenue. The original I-17 bridge was opened to traffic in 1962. Working in phases, crews earlier this year demolished the old southbound structure to make room for the area where these new girders are now located. Freeway traffic is currently shifted and thus temporarily sharing the existing northbound side of the bridge.

ADOT’s project team plans to complete the modernized southbound side of the bridge early next year. That’s when all I-17 traffic in the area will be shifted to the new structure so that reconstruction of the northbound side can move ahead. 

That second major phase in 2021 will include placing an additional 27 of these big girders to provide a wider bridge that will be able to accommodate more lanes along I-17 when future funding is available. So there’s still lots of heavy lifting ahead at I-17 and Central Avenue. 

You may have noticed, but we like to show you photos of our ongoing construction projects. 

Partially it's because we get some great shots as asphalt goes down, girders go up, rocks go "boom" or signs go in. But it's also because it's not always easy to see progress being made as you are driving through a construction site to get home, to work or to wherever you might be heading.

That might be the case with the current phase of our project to replace the Interstate 17 bridge at Central Avenue. Some parts have been noticeable; anyone driving on the I-17 in central Phoenix will have noticed that since June the road has been narrowed to two lanes in each direction and traffic has been using only the northbound side of the old bridge. You may also have seen when demolition work on the southbound bridge was ongoing earlier this summer.

But the photos to the right show something that's a little more difficult to notice: Crews hard at work building the piers that will eventually support the new southbound bridge. While this new structure won't be finished until early next year, you can see that progress is definitely happening.

Once the new southbound bridge is finished, there will be more noticeable changes. Traffic will be switched to the recently finished structure, and then it's the northbound side's turn to be knocked down and built back up. The project is schedueld to be completed in fall 2021, so drivers should continue to expect delays in the area while I-17 is narrowed to two lanes in each direction. They should also consider using Interstate 10 if they are going beyond the downtown area. 

As part of the $13.5 million rebuild, we are improving upon the original bridge that has serviced drivers since 1962. The new bridge will raise the clearance on Central Avenue from 14 to 16 feet, which will also allow for the future extension of the Valley Metro light rail south of the downtown area. Plus, the structure will be wide enough to accommodate future work to add auxiliary, or merge, lanes along the right shoulder of I-17 in both directions between the on- and off-ramps at Seventh Street and Seventh Avenue.

We think you'll also notice – and appreciate – that.

It’s happening!

The new diverging diamond interchange (DDI) at Interstate 17 and Happy Valley Road is scheduled to open to motorists sometime in mid-October.

The innovative Arizona Department of Transportation interchange paves the way for a slew of benefits: Better traffic flow, fewer “conflict points” between traffic traveling in opposite directions and thus, improved safety.

ADOT has worked closely with the city of Phoenix and Maricopa Association of Governments (the Valley’s freeway planning agency) in designing and now building the state’s first major diverging diamond interchange. The DDI design has been growing in use across the country for its innovative features. 

As mentioned above, diverging diamonds provide safety benefits by reducing the number of conflict points at intersections within the interchange. Those are locations with opposing directions of traffic. A potential conflict exists every time a vehicle crosses or turns across the path of another direction of traffic.

For example, at the Happy Valley Road DDI, intersections and traffic signals will allow drivers to cross to the left side of the bridge over I-17 and thus have a direct turn onto the freeway on-ramp. They are able to make that left turn without facing traffic in the opposite direction.

Reducing such conflict points as well as overall traffic-signal movements also allows more traffic to move through the interchange in a shorter amount of time. That helps to limit wait times for drivers, especially during times of busier traffic.

While you may be unfamiliar with such an interchange, studies and observations in other states have shown motorists quickly get the hang of traveling in a DDI. The use of noticeable pavement markings also helps direct traffic. You can see how it all works in the video to the right..  

ADOT State Engineer Dallas Hammitt discussed the benefits of a DDI in a blog earlier this year about two smaller diverging diamonds (called “half DDIs”) now in use along the Loop 202 South Mountain Freeway.

“This type of interchange works by temporarily transitioning traffic to the left side of the road, allowing through-traffic and left-turning traffic to proceed through the interchange simultaneously, eliminating the need for a signalized left turn.”

Crash rates improved dramatically after a diverging diamond interchange was constructed in Springfield, Missouri, according to the Federal Highway Administration. The study compared crashes from the first year after construction to the five-year average before, and found the following:

• Left-turn crashes were totally eliminated.
• Right-angle crashes were reduced 72 percent.
• Rear-end crashes were reduced 29 percent.
• Total crashes were reduced 46 percent.

“Where they have been built,” the FHWA report said, “travelers save time, agencies saved money, and communities will benefit from safer facilities for many years.”

There's an idea out there called creative destruction. It basically says that tearing down the old is sometimes necessary to make way for the new. This has been applied to everything from economics to the arts, but we found it very fitting recently for our project on Interstate 17 over Central Avenue.

As you can see in these photos, crews spent a busy weekend recently tearing down the old southbound bridge. Now that the old bridge (built in 1962, by the way) is gone, we can go ahead and start building its replacement. Traffic was switched to using only the northbound bridge back in June. When the southbound bridge is finished early next year, traffic will be switched again to use that and the whole process of creative destruction will begin on the northbound side.

Drivers should continue to expect delays in the area while I-17 is narrowed to two lanes in each direction. They should also consider using Interstate 10 if they are going beyond the downtown area. 

But we aren't tearing down just to erect something similar in its place. The new bridge will raise the clearance on Central Avenue from 14 to 16 feet, which will also allow for the future extension of the Valley Metro light rail south of the downtown area. Plus, the structure will be wide enough to accommodate future work to add auxiliary, or merge, lanes along the right shoulder of I-17 in both directions between the on- and off-ramps at Seventh Street and Seventh Avenue.

Once the creative destruction is all over, we think you’ll like what we will have created.

The whole $13.5 million project is scheduled to wrap up in fall 2021. You can learn more on our website.