The “tall poles with boxes” you see on I-40 are actually part of the “511” system instituted by the Tennessee Department of Transportation.
The poles with boxes you see in this area on I-40 measure the “mass and speed” of traffic and report it back to the 511 system, news media, the help vehicles and law enforcement. They actually use radar (vehicles with a radar detector will detect a radar in operation), to measure this.
Also part of the 511 system are the live web cameras that you can look up on the internet to view actual traffic.
If you want traffic or road information, dial 511!
For an interesting review of the 511 system and how it is used, go to http://www.tdot.state.tn.us/tdotsmartway/schedule.htm., or do what I did and to to tdot.state.tn.us and type in a search for TDOT.
To me, this is truly amazing and I encourage you to look at the web site for additional, more detailed information both on the 511 system and how to use it to your advantage.