As ADOT employees, we naturally get a lot of transportation-related questions thrown our way by friends and family... it’s just something that comes with the job!

By far, one of the most frequently asked questions has to do with HOV lanes and why ADOT builds them after the freeway is constructed (we answer that one here, by the way).

But, another question we regularly get focuses on the rock landscaping surrounding our Valley freeways.

People want to know why we don’t just use trees and shrubs instead of rock. Others wonder why we landscape the area at all.

Well, here’s the answer...

The main purpose of all freeway landscaping is really a practical one ... it helps control erosion and dust.

According to ADOT’s Chief Landscape Architect LeRoy Brady, anything that breaks up the rainfall (such as rock landscaping) or has a root system and holds soil together is going to help handle erosion.

As for dust control, Brady says rock landscaping and other types of plant-based landscaping help simply by covering the dirt.

“Because you don’t have bare soil, you don’t have the dust. It eliminates the dust source,” he said.

The type of rock that’s used matters, too.

Brady says his department sponsored a study that researched what size and grade of rock would work best for controlling erosion. The study was completed about 23 years ago, but the information is still used today.

Not only does landscaping help with erosion and dust, it has the added benefit of improving the aesthetics along freeways!

Rock landscaping is less expensive to maintain than planting and trimming trees and shrubbery... and rocks don't exactly require a lot of water.

ADOT works with the local communities to determine how to enhance the scenery along the freeways. Take for example the landscaping project along the recently upgraded I-17 in the north Valley.

ADOT worked with the city of Phoenix to create the landscaping theme and settle on designs, which are created to reflect Arizona's heritage and environment.

Brady says "context-sensitive design" is an effort in transportation to design and construct environmentally sound projects that fit and relate to the community, “instead of something that’s foreign and has no relationship.”

Along I-17, great care was taken to create designs that really fit the community.

About 15 colorful landform graphics made of crushed granite have been created for the project. There are a few Gila Monsters that have now taken shape at the Carefree Highway interchange and along the slopes at the Jomax Road interchange there’s a design patterned after a Hohokam water bowl.

It’s a challenging prospect to take a landscaping pattern from paper to the extra-large canvas of a freeway slope...

The process starts with site visits. Crews use flexible PVC piping and rope to set patterns before using spray paint to outline the design on the ground. Metal edging is then used to create the borders for the different sections of the colored rock and then the rocks are put in place.

Landform graphics and rock landscaping aren’t the only affordable and sustainable options for our freeways.

The location of the freeway often plays a role in determining what type of landscape to go with, as it did on a recently completed stretch of Loop 303.

There’s a lot more to freeway landscape design that we’ll cover in future blog posts. In the meantime, check out ADOT’s Roadside Development Web page.

It’s not often that a tree gets wrapped up in a mystery, but a lot of unanswered questions surround one Juniper growing next to I-17.

Some Arizonans might already know about the tree – it’s actually sort of famous around the state. Sitting in the middle of the median, just north of the Sunset Point rest area, around milepost 254, this is the tree that’s secretly decorated around Christmas and the Fourth of July. For years, no one has been able to figure out who is responsible.

Earlier this month something else happened that’s equally puzzling …

On Aug. 3, the 20-foot high tree survived a brush fire that had already consumed much of the vegetation around it. Flames got so close to the tree that plastic pipes situated near the trunk were melted (the pipes serve as a watering system and were put there presumably by the same people who stealthily decorate the tree each year).

The fire started about 200 feet south of the tree and forced a closure of the highway. But, according to ADOT Highway Operations Supervisor Randy Skinner , the tree, amazingly, was not harmed.

“The fire pretty much just burned up to the tree and burned out,” said Skinner, adding fire departments from Mayer and Black Canyon City responded to the blaze.

This isn’t the first time something like this has happened.

ADOT employees, who handled traffic control as the fire burned, have seen the tree somehow survive over and over again.

“In the 15 years I’ve been with ADOT, we’ve had fires three or four times a year and the tree never gets touched by the fire,” Skinner said. “For some reason this tree doesn’t burn.”

So, what do you think protects the tree? And, any ideas on who decorates it for the holidays? Leave your theories in the comments or post them over on our Facebook page!

Memorial Day weekend is here and if you’re headed out of town you probably have your travel plans all wrapped up by now.

Hopefully those plans already include some safety preparations … if not, here are a few things to think about before hitting the road!

• Check out your vehicle’s condition before a trip. Inspect things like tire condition and pressure, oil and other fluid levels and inspect belts and hoses.
• Pay attention while out on the road and expect the unexpected.
• Get plenty of rest before traveling and take regular rest breaks.
• Be patient and alert to changing road conditions … and buckle up!
• If your vehicle breaks down or you need to change a flat tire, pull completely off the roadway. Be cautious in areas with taller grass or brush – hot vehicle components can spark a fire.
• Don’t drive under the influence of alcohol or drugs (even prescription drugs can limit your ability to safely operate a motor vehicle).
• Cell phones or satellite devices help in an emergency – make sure they are fully charged.
• Obey the posted speed limit and check for changing speed limit conditions.
• Signal in advance for lane changes and turning maneuvers.
• Take plenty of food and water.
• Slow down in areas known for high winds and dust storms and be prepared to exit the roadway if extreme weather conditions occur. Weather conditions can change and monsoon storms can arrive suddenly, creating dust-filled winds and cutting visibility along the highway up ahead.

It’s always a good idea to allow some extra travel time, too. Unscheduled closures due to crashes or other incidents, including wildfires, can affect highway travel. Existing work zones for highway improvement projects, even when work is not taking place over holiday weekends, can add time spent on the road.

A couple of existing highway work zones to be aware of – especially at the start and end of the Memorial Day weekend – are located along Interstate 10 at the Hassayampa River bridges 40 miles west of downtown Phoenix and at the Interstate 17 bridges at Munds Park 20 miles south of Flagstaff. The highways are narrowed to one lane in each direction at those locations.

One last thing … before your trip you can call 5-1-1 or log on to ADOT’s Traveler Information site at az511.gov to check on updated highway conditions around the state.

The bridges over Pinewood Boulevard in Munds Park have been carrying Interstate-17 traffic for the past 53 years and now it’s time for some well-deserved reconstruction!

ADOT has already begun the project that will rebuild the bridges and ramps on I-17 at Munds Park, an area just south of Flagstaff . Work started last month and is scheduled to wrap up by fall 2012.

When the job is finished, motorists will have two new bridges each measuring 100-feet long (they’re now just 25 feet). The bridges will also be wider to accommodate an eventual third lane planned for I-17. A new sidewalk on Pinewood Boulevard is going in, too. It will allow pedestrians to cross safely underneath I-17 (see above video).

This update is necessary because there is more traffic now then when the bridges were built in 1958. Back then there was no development in Munds Park . The bridges are just inadequate for today’s traffic.

Drivers should expect some slowing of traffic due to this project – especially over busy holiday weekends. It is expected that delays at peak holiday travel times could reach up to 45 minutes … so please plan accordingly.

Project Timeline

April 2011 - Oct. 2011: The northbound bridge will be demolished, then reconstructed and I-17 will be repaved through the work zone. Because the northbound bridge is closed, motorists traveling northbound on I-17 will be directed to a detour that crosses over the median and utilizes southbound lanes. All on and off ramps will remain open.

April 2012 - Oct. 2012: The southbound bridge will be demolished, then reconstructed and I-17 will be repaved through the work zone. While this work is being done, the southbound bridge will be closed and motorists will be detoured over to the northbound lanes of I-17.