Transportation Defined: Passive Acoustic Device

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!