Back in the early 2000s ADOT started to hear from drivers who said certain stretches of Valley freeways seemed quieter than others.

ADOT and the Maricopa Association of Governments (MAG) noticed a difference, too.

It seemed that areas paved with an asphalt rubber friction course (rubberized asphalt), which MAG funded through the Regional Transportation Plan, were less noisy than freeway surfaces with cement concrete pavement.

ADOT set out to determine whether the rubberized asphalt really did make any difference when it comes to noise abatement. ADOT officials also wanted to know whether the perceived noise-reducing properties of the rubberized asphalt would last as the pavement aged.

Quiet Pavement Pilot Program

After some initial studies showed promise, ADOT, in connection with the Federal Highway Administration, developed the Quiet Pavement Pilot Program in 2003.

The program allows ADOT to use rubberized asphalt on selected freeway sections in the Valley in order to test out and study its noise mitigation properties.

According to the FHWA description, the program is intended to “demonstrate the effectiveness of quiet pavement strategies and to evaluate any changes in their noise mitigation properties over time. Current knowledge on changes over time is extremely limited. Thus, the programs will collect data and information for at least a 5-10 year period, after which the FHWA will determine if policy changes to a state DOT’s noise program are warranted.”

In other words, this study is going to show whether or not the noise mitigating effects of rubberized asphalt last the test of time.

That’s important to know because right now state DOTs cannot consider rubberized asphalt as a method to lessen highway noise. Noise walls and other tools are used primarily to meet noise abatement requirements.

If this study proves rubberized asphalt helps alleviate some road noise over years of use, states could potentially start using rubberized asphalt as an additional tool to help build quieter roads.

Findings to date

The study has shown so far …

Rubberized asphalt works best at high speeds and for average-sized passenger vehicles. It doesn’t have as much of a quieting impact at slow speeds or for larger trucks or motorcycles It’s not a solution for all climates Rubberized asphalt produces an average noise reduction of about 4 to 5 decibels over time.

Where we are today …

We have about three years remaining in the pilot study and we want to hear from you … the people who drive on Maricopa County freeways.

Public comment is an important part of the pilot program. ADOT has committed to collect and document public reactions on the rubberized asphalt for the study.

You might say each ADOT road construction project is a sum of its parts …

After all, you can’t build a road or a bridge without materials like aggregate, cement, and other structural materials.

But did you know each of those components must adhere to certain specifications? Some of the requirements are spelled out at a state level, while others are determined by the Federal Highway Administration and American Association of State Highway and Transportation Officials.

Because project engineers and contractors don’t have the time to evaluate all the materials and traffic control products on the market, the ADOT Research Center’s Product Evaluation Program is designed to assist them.

ADOT’s Research Center maintains the “approved product list” (APL), which contains products found suitable for use in highway construction in Arizona. The list is updated every month and contains products that have been evaluated and found acceptable by ADOT.

The approved products list is NOT comprehensive. It’s not an endorsement list, either.

Contractors can and do use products not on the list … those products just may require proof of third-party testing before it’s OK’d for use on a project.

How it works …

Vendors submit an application to the Product Evaluation Program manager. (Until recently, applications were mailed to ADOT. Now vendors email their applications and work is being completed to automate the process even more.)

Once an application is received, the product is assigned a product identification number, and then it may be assigned to an evaluator if a category exists for the product.

It is evaluated and the results are presented to one of two committees …

There’s the Traffic Control Product Evaluation Committee and the Materials Product Evaluation Committee. Each committee meets every three months and is responsible for approving or disapproving products on the APL.

If approved, a product will typically remain on the APL for about five years before it must be recertified. If product changes have occurred, then ADOT may reevaluate the product or request a new application if the product has changed significantly.

Product Evaluation Program Manager Stephanie Huang says it can take at least three to six months for a product to be evaluated and submitted to committee. According to Huang, 145 products have been assigned product identification numbers so far this year, which is up from 117 in 2010.

It’s been just about six months, but today the residents of Mescal and J-Six Ranch got their bridge back and can finally say goodbye to one lengthy detour!

These two Cochise County communities had been linked together by an overpass that spanned Interstate-10. But back in March, two semi-trucks collided underneath that bridge and the resulting damage was so severe that the connection between Mescal and J-Six had to be closed for safety’s sake.

Fast-forward to today ... a brand new bridge is in place, ready to accommodate the motorists who have been forced to take the long way whenever they needed to drive between the two neighborhoods.

“For most motorists traveling I-10, this closure was an inconvenience,” says ADOT Director John Halikowski in the video above. “It meant they’d have to travel a little farther to stop for gas. But for the communities of Mescal and J-Six Ranch, the overpass closure created a heavy burden. You see, the bridge is the only road connecting Mescal and J-Six Ranch. Residents from both sides were cut off from the businesses and services they rely on.”

Normally a project like this would have taken up to two years to complete, but ADOT put this job on the fast track because of the hardship the closure caused to local residents (motorists were seeing about 14 miles added to their round trips just to get across the road, which really starts to add up after a while).

The accelerated project started with the demolition of the old, damaged bridge. ADOT was able to take advantage of a previously scheduled April 8 closure of I-10 for the demolition of the nearby Marsh Station Bridge and was able to take down the Mescal/J-Six Bridge the same night.

An expedited design timeline also helped speed things along. An abbreviated bid process that focused on contractors with a track record of building bridges under emergency circumstances kept things moving, too.

The project received $955,000 in emergency funds from the Federal Highway Administration and construction was able to get started right after Fourth of July weekend.

Work included the placement of 35 new concrete box girders atop the bridge piers. Outside support beams were also placed, but they featured attached, precast bridge barriers designed to help expedite the construction.

Amazingly, by Sept. 9, crews were already prepared to pour 150 cubic yards of concrete for the 216-foot-long bridge deck.

The concrete took 10 days to cure and you’d better believe crews didn’t let that time go to waste! They continued to work by filling gaps in the barrier wall between box girders and putting the finishing touches beneath the overpass.

The very final step taken before the bridge could open to the public included placing temporary markers along the lanes (permanent striping will be added to the roadway at a future date).

We’ve followed the progress of this project through videos and blog posts and now that the bridge is open, we hope you’ll take a look back at what it took to get here! As you can see in the video above, this bridge is important to the two communities it connects.

We at ADOT would like to thank all the residents, business operators, as well as Cochise County officials for their patience and support!

Note: This blog post was updated to reflect a revised open date for the bridge. It opened Monday afternoon, about 16 hours ahead of its Tuesday scheduled date.

          Photos courtesy of the Arizona Game and Fish Department

Over the past several years, ADOT has worked to transform the highly traveled US 93 between Wickenburg to the Hoover Dam from a two-lane highway to an environmentally friendly four-lane, divided highway.

A project of this scale will always present its share of issues, but widening the final section – from Kingman to the Mike O’Callaghan - Pat Tillman Memorial Bridge – provided ADOT with an especially unique challenge …

That final stretch also happened to be the stomping grounds of the country’s largest contiguous herd of desert bighorn sheep.

Without some sort of solution, motorist safety would be at risk from the substantially increased chance of wildlife-vehicle collisions. But the sheep still needed to be able to cross the highway in order to reach essential resources on both sides.

Wildlife overpasses were thought to be the obvious fix … but, where should they be built along this 15-miles of new roadway?

To answer that question, ADOT worked with a number of state and federal agencies in a collaborative partnership to seek locations where the sheep were most likely to cross the highway. The Arizona Game and Fish Department, National Park Service, Bureau of Land Management and the Federal Highway Administration were all part of the effort.

The team was able to track the animals by placing electronic collars on them and using global positioning system tracking units to trace their movements over an extended period of time.

This research helped identify the most appropriate crossing locations for the herd. Three specially designed overpasses for bighorn sheep – the first of their kind in Arizona and the lower 48 states – were constructed, along with fencing, as part of the highway expansion.

The project has been successful. Cameras installed on the crossing bridges captured the desert bighorn sheep using the new overpasses, which are 100-feet wide and 203-feet long and the Federal Highway Administration awarded ADOT one of its top environmental honors, the 2011 Exemplary Ecosystem Initiative Award, for the successful completion of this project.

ADOT’s Director of Environmental Services Todd Williams says the project was truly a joint effort of the multiple agencies involved.

“Without their support and teamwork, we would not have been able to accomplish as much as we did,” he said. “This new section of divided highway in this environmentally sensitive area delicately addressed two critical issues: the safety of the traveling public and the need to preserve the livelihood of the Desert Bighorn Sheep, which are native to the Black Mountains. These new wildlife overpasses helped accomplish both objectives on this project.”