Does merging on the highway pose a dilemma for you?

For a lot of us, a “Merge Left (or Right)” sign triggers an inner debate: Should we politely do what the sign says and merge now, or should we wait to merge later – and gain more ground – but feel guilty for cutting?

The zipper merge system ends the debate and encourages drivers to wait until the last minute to merge – without guilt!

What is the zipper merge, you ask, and what does it have to do with ADOT?

Glad you asked! No, it’s not a new line dance or a carnival ride, but a traffic system that organizes how motorists merge when a lane closes.

ADOT has been using the zipper merge on various projects since 2016. Currently, it is being used on the Meteor Crater and Two Guns bridge deck replacement and rehabilitation project on Interstate 40 east of Flagstaff.

Okay, but how does it work?

Here’s how, according to AAA. The zipper merge is like a zipper on a pair of jeans. Just as the teeth of your jean’s zipper come together, the zipper merge keep traffic coming together, smoothly closing the lane.

Motorists stay in their respective lanes until the final merge point, which is efficient because it’s not leaving one lane empty. It uses all available lane space.

At the merge point, vehicles take turns merging: The car in one lane merges, and then a car in the other lane merges, then the car in the next lane merges, and so on. Like a zipper!

Additionally, ADOT is testing a “smart work zone” in the westbound direction of the I-40 project. It uses a dynamic merge system with electronic signs and sensors and can be controlled remotely. When traffic is light, the signs ask motorists to merge well ahead of the closure. When traffic is heavier, the zipper merge system kicks in and signs ask drivers to merge later. You can read more about it here.

Dilemma resolved!

For more information about the zipper merge, check out this classic ADOT blog.

To see photos of the I-40 bridge deck and rehabilitation project, visit the ADOT Flickr album.

We who oversee the ADOT blog love it when new constructions gets underway, mainly because we get to dive deep into the process of taking a project from idea to fully finished road.

That's the case right now with the interim expansion of State Route 24 from Ellsworth Road to Ironwood Drive in the southeast Valley. Preliminary work kicked off before the holidays, but now that it's a new year, drivers can expect to see construction in earnest. 

Which brings us once again around to taking a look at highway construction. Part of the work people might see happening right now is construction of a box culvert near Williams Field. 

Okay, so box culverts. You've probably seen them all your life, but haven't given them much thought. We don't blame you. On the scale of engineering complexity, their design is kind of simple. But that contrasts with their function, which is an all important concern when it comes to road building: moving water. The purpose of a culvert is to help water flow along a channel in such a way to keep it from washing away a road or a bridge. They can come in a variety of shapes - for example round or square - and materials - like either concrete or metal. Depending on a variety of factors such as an expected flow of water, you can have one culvert or multiple ones together. 

We think you get the point. Box cuverts: simple, yet super important. Let's now tie it back to where we started, the ones being built on SR 24 near Williams Field.

The photo here gives you a little perspective on how you go about installing culverts. For reference, the image you see is the inside of the culvert. One of the first things you'll notice is the wooden bracing inside. As we told you about in another blog, that's called falsework. It's job is to help hold up the shape of the culvert until the cement is dried and the whole thing is self supporting. That's what happening here; cement was being poured for the walls and deck the day this photo was taken. 

The blog we just mentioned will also teach you about sand jacks and how the falsework is removed after the cement sets. We may be a bit biased, but we think its pretty fascinating.

With construction expected to last through fall of 2020, expect to see more work like this as we extend two lanes of highway in each direction between Ironwood and Ellsworth, and add bridges over Ellsworth and Mountain roads with additional intersections at Williams Field, Signal Butte and Meridian roads. And, as with all highway projects, you can sign up for traffic alerts and other updates on the project page on the ADOT website. 

If this small glimpse has not scratched your box culvert itch, you can check out the full Flickr gallery of the construction below.

As a new year begins, so will a new freeway project in the southeast Valley. Work on the addition of a new Loop 202 Santan Freeway interchange at Lindsay Road, east of Gilbert Road, will start this month.

To mark the start of construction, the town of Gilbert hosted a groundbreaking ceremony in the area near where new on- and off-ramps will be added along the Santan Freeway at Lindsay Road. Gilbert’s event team should be applauded for arranging and carrying out a socially distanced ceremony with precautions taken during the current health situation.

Officials from Gilbert, including Mayor Scott Anderson, spoke about the work of various agencies over time to make the project a reality as well as the benefits that a new interchange will provide for local drivers and the town’s economic development opportunities.

ADOT’s State Engineer Dallas Hammit also took part in the groundbreaking and focused his remarks on how this project is an example of partnering and cooperation between local, regional, state and federal agencies.

Over approximately the next year, ADOT will now manage a $21.7 million project to add the Lindsay Road interchange. Completion is anticipated in early 2022. Other improvements include the widening of the westbound Loop 202 off-ramp at Gilbert Road and eastbound off-ramp at Val Vista Drive and construction of a new westbound frontage road between Lindsay and Gilbert roads.

Gilbert will complete local street improvements in the area. Both ADOT and Gilbert will provide project updates, including traffic restriction reports, as the construction moves forward. Minimal restrictions are expected along Loop 202 during the course of the project since much of the work will take place away from the freeway’s lanes. We urge drivers to use caution and to always watch for workers and equipment in freeway or local street work zones.

As State Route 189 construction progresses from the international border of Mexico to Grand Avenue in Nogales, monarch butterflies are emerging throughout the new highway structures. 

Abstract butterflies are cascading down the concrete piers being installed for the new bridge and flyover ramps connecting SR 189 and Interstate 19.

“This design shows how these butterflies cluster together on tree trunks,” said Landscape Architectural Designer Joseph R. Salazar, who is the project aesthetic manager. Three-dimensional metal butterflies will be attached as accent icons on the concrete retaining walls. Abstract butterfly designs also will be incorporated in landform graphics. 

Why were butterflies chosen as the project’s aesthetic theme? 

ADOT roadside development team members studied the cultural, historical and biological contexts in the Nogales Port of Entry area. They learned that SR 189 is also known as Mariposa (Spanish for butterfly) Road. In addition, the North American monarch butterflies are significant in this region — migrating through Arizona between Mexico and Canada in the fall and spring. 

“I decided to incorporate the monarch butterfly because it represents movement and transportation, which ties in with the busy Nogales Port of Entry that has a lot of trade going back and forth,” Salazar said. 

The monarch butterflies’ bold colors and shapes echo the vibrant colors, cultural and natural beauty of the area. Monarch butterflies are under consideration by the U.S. Fish and Wildlife Service for inclusion on the Endangered Species List.

The SR 189 landscaping will benefit monarch butterflies because milkweed shrubs — the primary food source for monarch caterpillars — will be part of the vegetation. Roadside Resources Specialist Kris Gade is part of a group that developed a nationwide candidate conservation agreement for monarch butterflies to conserve and enhance monarch butterfly habitat, including providing vegetation they need to survive, such as milkweed. 

“ADOT supported development of the agreement and is working on identifying monarch butterfly habitat areas in rights of way around the state,” she added. 

View more photos of the butterfly design in the SR 189 highway on the embedded Flickr album. Read more about the highway improvements and see a video with a butterfly’s view of Mariposa Road. 

One of ADOT’s major priorities while rebuilding the I-10/Houghton Road interchange is to minimize disruptions and closures, which means we’ve got to move really fast when we close a roadway.

If you’ve driven through that interchange in the last couple months, you’ve seen that our crews have moved so quickly that they’ve transformed the landscape on half of the interchange in less than two months. This photo from the project team shows the work so far, including constructing bridge piers for a new overpass on the west side of the interchange, regrading everything on the east side of interchange and building up the earth for new ramps.

That’s a lot of progress for a project that kicked off Aug. 24.

We closed two of the interchange’s ramps in late August, with a goal of rebuilding and reopening them before Thanksgiving. Those ramps – the westbound exit ramp and eastbound on-ramp – are already taking shape and should be paved by early November.

We’ll rebuild the ramps on the west side of the interchange as well, but they will remain open through the project except for an occasional nighttime restriction or closure. Likewise, only occasional overnight restrictions and closures will be needed on Houghton Road. And, I-10 will remain open, though drivers should expect overnight lane restrictions at times.

The new $24.4 million interchange east of downtown Tucson is expected to be complete in late 2021. It will feature southern Arizona’s first diverging diamond interchange – a type of interchange where drivers cross and travel on the left side of the overpass while crossing the interstate.

You can read more about the I-10/Houghton Road project and diverging diamonds here. And if you’ve driven through north Phoenix recently, you may have noticed ADOT opened Arizona’s first major diverging diamond interchange earlier this month at I-17 and Happy Valley Road. The Phoenix interchange won’t be fully complete until late this fall, but the major elements are in place if you’re looking to get a feel for what’s coming to I-10 and Houghton Road in southern Arizona next year.

We have quite the talented group of shutterbugs here at ADOT, as evidenced by the quantity and quality of the highway construction photos you can easily find on our Flickr page.

If you have paid any attention to our Throwback Thursday blogs, you know that we also have a rich archive to draw on to see what construction was happening decades ago. Between both, there are thousands of photos that are each capturing a moment in time, showing us the people, places and equipment that came together to build the transportation infrastructure we enjoy today.

That's why we like this photo so much. As the caption says, this was taken during paving operations on February 26, 1934 on an unnamed stretch of Thomas Road. You can immediately spot the plethora of differences that has taken place in the last nearly 90 years. There's the equipment, the old cars in the background and the wooden telephone poles running the length of the street. Can you imagine visiting a construction site in a three-piece suit and fedora?

Also, how about that street? In 2020, Thomas Road is a major route that runs – with some gaps – between 144th Avenue in Goodyear to Power Road in east Mesa, cutting through much of the heart of the Phoenix metro area. It's come a long way from the dirt-packed, house-lined path that we see here.

This photo is interesting to us because today ADOT oversees state highways and freeways. But apparently, at this time, the then-named State Highway Department was interested in the paving happening along this city street. 

There's a lot to unpack in this photo, but it does raise an interesting question: What will future ADOT bloggers say about the photos we're taking now for the construction on I-10 at Ruthrauff or I-17 and Happy Valley? 

Highway construction is and has been labor-intensive, but after we found this photo we couldn't be happier to be living in our modern, mechanized age.

Because these folks here driving the livestock are not farmers out plowing a field. They are actually Arizona Highway Department crews in the process of grading a highway. US 60 between Salome and Aguila, to be exact. This mule-driven photo is from Dec. 7, 1933.

As you might know, grading is the process of smoothing the base layer of a road to remove divots, washboards and other high or low points. For dirt roads, such as this stretch of US 60 (which would also be co-signed with US 70 for a time), grading is basically all the roadwork and maintenance that is done. Today construction crews have grading machines for this type of work. We can only imagine those machines are a bit more reliable than the mules and produce less ... um ... waste.

The year this photo was snapped is significant because it was actually a bit of turning point for highway construction in Arizona. According to our report on the state's transporation history, that year the federal Public Works Administration gave Arizona $5.2 million for road projects, which covered hundreds of miles of grading and draining, oiling, sealing and paving, along with bridge construction, shoulder-widening and railroad-crossing construction.

By 1933, Arizona was also the leading state in the West when it came to oiling, or spraying "low-type bituminous surfacing" on, gravel roads. At the start of the year, more than 1,000 miles of state highways had been oiled, and when State Route 87 in Chandler was surfaced, for the first time a person could drive between Phoenix and Tucson without driving on a single stretch of a gravel road. At the end of 1933, the state reported that all its highways, with limited exceptions, had been oiled or actually paved.

That's all fascianting for us, but it most likely meant little to our mule-driving friends here, who were probably just happy if their stubborn charges kept the grader moving.

The important ongoing project to reconstruct the Interstate 17 bridge over Central Avenue south of downtown Phoenix remains in an early stage. But before the work got started, our staff at ADOT knew the bridge work zone would present challenges for drivers who use the stretch of I-17 between the I-10 “Stack” and “Split” interchanges.

A decision was made to incorporate a “Smart Work Zone” safety innovation into the I-17 project at Central Avenue. As you can see in this ADOT video, the project team has followed through with the placement of portable message signs on trailers at nearby freeway locations to provide drivers with travel times for both I-10 and I-17 in the downtown area.

For example, one of our message signs along westbound I-10 near Phoenix Sky Harbor International Airport provides both I-10 and I-17 travel times. That allows drivers to compare the estimated travel time for using northbound I-17, which includes the work zone, or what to expect by staying on I-10 in the downtown area.

On average, the optional I-10 route that includes traveling through the Deck Park Tunnel is saving drivers five or more minutes of commute time, not to mention avoiding the frustration associated with slow moving traffic in a work zone. Even with lighter traffic conditions on freeways during the current health situation, there are times when slow downs and backups occur on I-17 in the area approaching the bridge work at Central Avenue.

The portable sign system uses traffic data to calculate the estimated travel times to predetermined destinations. This system is much like the one used to provide drivers with valuable travel times on ADOT’s permanent electronic message boards along Valley freeways.

As part of this pilot project, portable message boards also have been placed in areas along I-10 approaching interchanges connecting to the new Loop 202 South Mountain Freeway. Those signs also provide drivers with estimated travel times for using either Loop 202 or I-10 through the downtown Phoenix region.

ADOT has recently established several Smart Work Zone initiatives to help offset challenges associated with keeping traffic moving while construction is taking place. Those innovations include an I-15 queue warning system in the Virgin River Gorge, providing drivers with information to prepare for stop-and-go conditions ahead. Another example is the I-40 dynamic merge system east of Flagstaff that adjusts methods for merging depending on conditions near a bridge project at Meteor Crater.

EDITOR'S NOTE: During this unprecedented time, ADOT is creating transportation activities for kids. Please visit azdot.gov/ADOTKids or use the hashtag #ADOTKids on ADOT's Twitter, Facebook and Instagram accounts to see what we have going on.

By Steve Elliott / ADOT Communications

I hope you've enjoyed our latest ADOT Kids activity focusing on the Loop 202 South Mountain Freeway and how we use designs and landscaping to make freeways nice places to be. Please remember to send us your freeway design art by 5 p.m. Wednesday, May 13, so we can include it in our slideshow of everyone's work.

If you've finished your design and are looking to do something else fun, some creative people I work with have come up with a word search and a construction zone maze. Depending on your age and interests, you can print one or both by clicking the images below.

You'll find these and other activities at the ADOT Kids home page, azdot.gov/ADOTKids. 

Have fun, everyone!

South Mountain Freeway word search:

Work zone maze: