[wideminded]

Where do folks think that they get the information on the freeways for the signs that tell you how many minutes to major exits/interchanges? They have to be calculating off of the toll tags to see how long it takes for specific cars to cover the distance, and then posting it to the electronic boards in near real time.

I have never heard any other claim that these figures referred to "specific cars". That would not even be that helpful because highway conditions are constantly changing. The figures are determined/estimated by monitoring traffic flow everywhere along the highway at the same time.

[PAR35]

What the state department of transportation says they use:

“The units are Smart Sensors manufactured by Wavetronix. The Smart Sensor is a digital wave radar used for vehicle detection. The Smart Sensor measures vehicle volume, occupancy, speed and classification. The information gathered is NOT used for law enforcement purposes. We use the information to generate the speed map shown on our web site and to generate the travel times displayed on the dynamic message signs on the freeways.”

This one hasn’t passed - for now:

“The Texas legislature considered a bill that would have required all state vehicle registration stickers to have RFID spy chips” https://blog.mysanantonio.com/terrihall/2013/10/toll-tags-tracking-big-daddy-government-coming-to-a-road-near-you/