July 1 is not only the beginning of a new month, one in which Arizona experiences its hottest average temperatures, but it’s also a very important day for us. 

Today is ADOT’s 48th Birthday!

To celebrate, let us take a trip through the years and recount the agency’s history through our instantly-recognizable logos.

When The Arizona Department of Transportation officially emerged from the Arizona Highway Department in 1974, our logo consisted of a state shield and two vertical lines in a beautiful shade of copper. One vertical line is for highways and the other represents a runway. Did you know that ADOT owns and operates the Grand Canyon National Airport?

The copper logo served us well for 21 years until 1995 when ADOT’s graphic arts team developed nearly 60 ideas for a brand new logo. Those 60 were pared down to six and ADOT employees chose the emboldened Saguaro hovering above a sapphire-shaded Arizona with 43%. While definitely unique and maybe even a bit funky, these tints of blue only lasted four years.

In 1999, ADOT adopted a logo that would take us into the new millennium. The plum and teal design that features two interlocking highways with mountains in the distance and the agency's initials "ADOT" below. The logo is indicative of the beautiful southwest and was revealed to commemorate our 25th year as a state agency. In 2012, this logo was tweaked slightly, removing the road-mountain emblem and leaving only the "ADOT" as ADOT had morphed into a multi-modal agency with more priorities than only roads.

That brings us to today. Our current blue logo continues the same design from the last 10 years, but streamlines it with a sleek, sophisticated look -- gone are the plum and teal colors. This one was unveiled in 2019 when ADOT celebrated our 45th anniversary and took on official usage in 2020.

Five logos and nearly one half-century later, ADOT continues to grow and provide the people of Arizona a trusted public resource.

Which one is your favorite? Let us know!

"The spandrel of an arch bridge is the area between the arch ring and the roadway. ... Open-spandrel arches have columns resting on the arch ring that support floor beams, which in turn carry the roadway."

We know what you're thinking: Uh, OK, what does that mean in plain English? Let's show you an example: Cienega Creek Bridge in Pima County.

Known as Arizona's longest open-spandrel bridge, the Arizona Highway Department -- a precursor to the Arizona Department of Transportation -- began construction of Cienega Creek Bridge began in 1920 as part of the new Borderland Highway (US 80) across southern Arizona. The bridge is located a few miles east of Vail, Ariz., and near a railroad.

Construction was finished in 1921. At 146 feet, Cienega Creek Bridge's open-spandrel arch is comprised of two tapered ribs that are anchored in concrete foundations with spread footings. 

The bridge was part of U.S. 80 from 1926 to 1955 and was put on the National Register of Historic Places in 1988. It is no longer a state highway and, today, carries local traffic on Marsh Station Road. 

Have you ever searched the Internet for videos of trucks using a runaway-truck ramp? If so, you might have seen this video:

A truck having to use a runaway truck ramp is a frightening thing to see. But truck ramps are very effective at stopping trucks that have lost use of their brakes. There are two types of runaway truck ramps:

1. Gravity ramps: A truck takes the ramp and experiences an uphill grade that naturally will stop it.
2. Gravel arrester beds: These are on a flat-level grade. Trucks taking the ramp will run into a bed full of small, round gravel. The friction from the wheels going through the gravel is what slows the truck and eventually stops it.

Why are they necessary? Here's a quick answer from ADOT’s Roadway Design Guidelines:

The combination of heavy trucks and steep highway downgrades presents a potential safety hazard... Defective or incorrectly adjusted braking systems on trucks or trailer, among other things, can contribute to brake overheating and failure resulting in the driver's inability to control vehicle speeds on downgrades. Truck escape ramps offer an opportunity for out-of-control trucks to exit the highway and come to a controlled stop.

For more details on runaway truck ramps, click here.

A truck striking the bottom of a lower-height bridge deck -- also commonly called an overpass -- can cause plenty of damage.

ADOT engineers had noticed that one problem area were I-17 overpasses in Phoenix. Trucks hitting overpasses at 19th Avenue, 16th Street and other locations were causing thousands of dollars in damage.

Enter the Central District and Regional Traffic Engineering teams. After exploring a few options, it was determined that a solution to this recurring issue was adding red-and-white reflective sheeting to the bottom decks of several I-17 bridges. This makes the bridge overpass stand out for trucks that don't meet the bridge clearance.

Sheeting was trimmed to fit the bottom edges of the bridges. Highway Operations team members installed the material on I-17 overpasses at 19th Avenue, Seventh Avenue, Seventh Street and 16th Street.

The team's ingenuity and perseverance paid off. Since the sheeting was installed last summer, there have been no bridge hits at those locations. Previously, overpass repairs at those locations totaled about $37,000 a year.

“The feedback so far has been very favorable regarding the visibility, cost and ease of installation,” said Highway Operations Superintendent Sean McHugh. “Based on this easier and lower cost process, standard work was created for low-height bridges that can be applied across the state.”

There’s a famous quote that says, “Without struggle, there is no progress.”  It’s a good one to keep in mind this weekend  if your travels take you along Interstate 10 in the metro-Phoenix region. You might struggle a bit with delays and longer-than-usual detours getting to and from your destinations. Two major closures will be in place beginning the night of Friday, April 22, through the early morning hours of Monday, April 25:

• I-10 will be closed in both directions between State Route 143 and SR 51 for the I-10 Broadway Curve Improvement Project; and
• Eastbound I-10 will be closed between Loop 101 (Agua Fria Freeway) and 75th Avenue as we continue to improve the pavement between Avondale Boulevard and I-17.

Both closures are necessary so we can make progress on two projects that will provide motorists with smoother driving surfaces and more travel lanes, while reducing congestion and improving safety. 

The decision to have two weekend closures on an urban interstate – including one that shuts it down in both directions at the same time – isn’t made lightly. Before any weekend work is scheduled, our project teams in the metro-Phoenix region map out every location on the state highway system where construction or maintenance activity needs to occur. All of the construction and maintenance teams meet to coordinate closures for the following month. They evaluate which directions of travel will be impacted, as well as the most efficient detour routes for high volumes of interstate traffic. They coordinate ADOT project schedules with road work that’s underway on local roads and streets, as well as with major special events that draw 30,000 or more people. 

At the same time, our project teams are required to follow their project contracts and keep work on time and on budget. That brings to mind another famous quote: “Sometimes you gotta do what you gotta do.” This weekend we’ve gotta do some very specific work so that both projects can move to the next phase. Bumping one of them this weekend simply wasn’t an option if we want to stay on time and on budget and make the highways better for everyone who uses them.

Our allowable times for major closures also impact when we can do major work. Unlike many other states, ADOT doesn’t close urban highways on weekdays. We schedule the highly impactful work during overnights and weekends, with the understanding that every cone and barricade must be picked up by 5 a.m. on weekdays so we don’t tangle up your morning commute. With weekday traffic volumes back to pre-pandemic levels in many areas, our commitment to maintaining open lanes during peak travel times continues. 

With the limited time available, our project teams complete as much work as they can under the umbrella of a weekend closure. For example, Salt River Project crews need to close I-10 along the Broadway Curve this weekend to relocate a 75-foot-tall, 17-ton power pole and the high-powered lines that span both directions of the highway. The massive pole stands in the way of where the new ramp from southbound SR 143 to westbound I-10 will be constructed. While the SRP closure is in place, workers will take advantage of the opportunity to repair the concrete-pavement driving surface in the project area, and shift the work zone. Combining all the work into one weekend means fewer closures later on – good progress.

Our work in the West Valley includes removing the existing asphalt pavement and repairing the concrete pavement to make the driving surface smoother. Making the improvements requires closure of a full set of lanes (again, eastbound this weekend). As someone once said, “You’ve got to take the good with the bad.” In fairness, someone also said “You’ve got to take the bad with the good.” Either way, you get the point.

As you plan to hit the road this weekend, remember another popular quote: “The best defense is a good offense.” Plan ahead. Check out detour routes in advance. Allow yourself plenty of extra time.

Lastly,  remember what the English soldier who founded the Boy Scouts said: “Be Prepared.” We encourage you to prepare yourself by downloading The Curve mobile app for updates on the I-10 Broadway Curve Project; visiting az511.gov; or downloading the AZ511 mobile app for real-time highway conditions. Then you’ll be ready to process the progress!

When ADOT builds a new bridge, our top priority is to make sure the gigantic mass of steel and concrete stays right where we build it.

But that won’t be the case with a new bridge we’re constructing on State Route 79 in Florence, because this bridge is designed to move.

Or more precisely, slide. 

This new bridge’s mobile nature will be only temporary, however, as part of an innovative method of constructing a new bridge by assembling the new structure’s components next to the old bridge and then sliding them into place.

The process begins by constructing new bridge piers in the bed of the Gila River. The piers will be extra wide so the new structure’s components can be built in halves on either side of the old bridge. Once the new segments are complete, crews will tear out the old bridge and slide each half of the new structure where the existing bridge now stands.

ADOT has slid new bridges into the place of old ones before, including a 2020 project to replace the Fourth Street bridge over Interstate 40 in Flagstaff.

By sliding a bridge into place, ADOT can keep traffic moving with minimal delays during construction. Both lanes of traffic will remain open during the SR 79 project, except for two weekends when the bridge halves are slid into place. On both weekends, a temporary traffic signal will restrict traffic to one lane in each direction.

The existing bridge was built in 1957-58 and has reached the end of its useful life. When ADOT began planning for a replacement, engineers had several options for its construction. 

One common method involves building the new bridge next to the old one, which was the case when ADOT replaced the Pinto Creek bridge on US 60 between Globe and Miami. That option was ruled out for the Florence bridge project because of the additional cost to buy right-of-way and shift the road to the new structure. 

Another approach is replacing the bridge one half at a time, which is how ADOT replaced the SR 77 bridge in Winkelman. That option would have meant only one lane of traffic would remain open during the project, which would have led to excessive delays because SR 79 carries significantly more traffic than the highway through Winkelman.

No matter what method ADOT chooses to replace a bridge, our goal is to maintain a safe and reliable transportation system while minimizing delays for motorists. In the case of the project in Florence, drivers should look for a reduced speed limit in the work zone and watch for traffic alerts when the bridge slides require two weekends of lane restrictions. 

Learn more about the project and stay up to date by checking out the SR 79 bridge replacement project page. 

Is there such a thing as TMI about TMAs? TMAs (truck-mounted attenuators) are also called crash cushions, but there’s nothing cushy about them when it comes to keeping drivers and workers safe. 

All kidding aside, we’re serious about your safety and that of workers during the state’s largest urban freeway reconstruction project, the Interstate 10 Broadway Curve Improvement Project. 

Attenuators, whether truck-mounted or fixed, are hard to miss (hint: the yellow and black stripes usually give them away) and you’ve probably seen them along the project area, which spans I-10 for 11 miles in both directions from the Loop 202 (Santan/South Mountain freeways) to Interstate 17. Additional work is occurring on one mile of eastbound and westbound US 60 between I-10 and Hardy Drive and on 1 mile of northbound and southbound State Route 143 between I-10 and the Salt River. 

The mobile TMAs act as a safety barrier between the workers on the job and freeway traffic. A project crew member parks the TMA behind the work crew; if a driver veers into the work site, the vehicle will hit the attenuator instead of a heavy truck or a construction worker. 

Fixed attenuators stay in one place in active work zones. They are usually installed near off-ramps or medians and anywhere a temporary barrier wall comes to an end. 

Fixed or mobile attenuators are designed to absorb the impact of a crash, protecting workers and helping to reduce injuries to motorists and damage to their vehicles. But anytime one is hit, people can be seriously injured. Also, the attenuator must be repaired or replaced right away, which is costly and requires additional lane closures and delays for drivers.

Work zones will be shifting throughout the length of the Interstate 10 Broadway Curve Improvement Project, and fixed attenuators will be added and removed as needed during construction. Mobile TMAs will follow and protect workers for the next three years. Watch for these as you drive through the project area! 

So please slow down, avoid distractions and give our attenuators your full attention. 

All about attenuators: /adot-blog/all-about-attenuators