There's a lot of useful information to be obtained from our roadways and loops help ADOT collect some of that data.

Loops are detectors embedded in the roadway to detect vehicle movement. These devices permit ADOT to determine traffic counts, density and vehicle speed.

This information helps traffic engineers make decisions and feeds ADOT AZ511.gov.

See also PADS.

Transportation Defined is a series of explanatory blog posts designed to define the things you see on your everyday commute. Let us know if there's something you'd like to see explained ... leave a comment here on the blog or over on our Facebook page!

You've probably never gotten a good look at the Passive Acoustic Devices (PAD) out on the freeways … they're easy to miss.

PADs are small objects that sit near the top of utility poles and are barely visible to drivers below, but they collect a lot of useful data.

PADs use microphones to “listen” to freeway traffic. These sophisticated devices can use that information to determine vehicle speed and density in an area. This information helps feed AZ511.gov.

Transportation Defined is a series of explanatory blog posts designed to define the things you see on your everyday commute. Let us know if there's something you'd like to see explained ... leave a comment here on the blog or over on our Facebook page!

Maybe you've noticed some of the cameras that are perched high above the roadways ...

These are Closed Circuit Television (CCTV) cameras and are used by ADOT's Traffic Operations Center (TOC) to constantly monitor traffic conditions throughout the state.

Most of these cameras can pan, tilt and zoom from any workstation at the TOC, which allows operators to get a closer look at traffic incidents and determine the appropriate response.

Several television stations have access to ADOT's live CCTV camera feeds to show freeway conditions.

The CCTV camera shown, like most, is installed with an important feature ... a lightning protection rod!

Transportation Defined is a series of explanatory blog posts designed to define the things you see on your everyday commute. Let us know if there's something you'd like to see explained ... leave a comment here on the blog or over on our Facebook page!

Have you ever spotted something on the highway and wondered, ‘what is that and why is it there?’

If you have, the ADOT Blog is here to help you find the answer!

We’re going to start periodically sharing short blog posts that identify and define some of the transportation-related objects, equipment and machinery you see out there on the road.

To make these posts easy to recognize, they’ll be tagged with a “transportation defined” label. We’ll also be linking back to these definitions in our more comprehensive blog posts to help better explain things.

And, of course we’d like to invite you to tell us if there’s anything you’d like explained. Let us know what transportation-related objects you’re curious about … just leave us a comment here or on our Facebook page!

Controller Cabinets:

Controller cabinets (see photo above) sit along the roadway and send information from things like ramp meters and loops to ADOT’s Traffic Operations Center. These cabinets are not air conditioned and all the equipment inside is “field hardened” to withstand Arizona summers.