How do they calculate travel times on the Illinois Tollways?

Over the weekend, I was driving on I-90 towards Chicago to go to the Cubs game. The traffic started to get congested as I got closer. I was hoping that I was early enough, so there wouldn't be a horrible back up.

Then, I saw one of the electronic signs that give driving time information. When I see one of those signs, I always try to keep track of the time to check if they're correct. I usually get distracted and forget.

Of course, I think how do they know? The tollway people don't know how fast I'm going. There's no way they can see and keep track of all the traffic.

Well, guess what? According to the, they do know.

  • "Traffic speeds and volumes are collected when vehicles pass through toll plazas, and by pavement sensors and detectors mounted on poles."
  • "The agency also uses technology to capture speed data from vehicles with Bluetooth. That information, officials stressed, is kept anonymous."
  • "The data is transmitted back to the Tollway's Traffic Operations Center, squirted through an algorithm and -- ta-da! -- displayed on message boards that are updated every three minutes or so."

Now, don't you wish you study harder in school? Maybe, I can actually use some of that math stuff in real life?

Next time you are traveling on I-90 to Chicago, test the signs to see if they are correct.

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