The system knows where you are supposed to be going and when you are supposed to arrive there. If it calculates that you have too far to go for the amount of time you have left to get there it will issue an alert to dispatch letting them know you seem to be running late. It will track when you arrive at the pickup point, when you opened the trailer doors, whether or not you drop the trailer, when you close the trailer doors, where both the truck and trailer are along the route, when you arrive at the destination, when you open the doors, and when you close them again.
The system will store all of this information permanently in case any of it needs to be known anytime in the future for any reason. You, your truck, your trailer, and everything you do related (or maybe not related to) your job is being tracked in real time and being stored permanently somewhere.
If the tracking system looses the signal from any of the tractors or trailers for some short specified amount of time another alert will be sent to dispatch letting them know the last time and location of the equipment and they can send the police if they like to determine if the equipment has been stolen and the devices deactivated.
For the sane amongst us let me assure you that once you get your CDL and set foot in a commercial truck your days of privacy, or perceived privacy, are long gone. You'll find out how true that is the first time you apply for a job at a large company. I can not prove that they are able to use FBI computers to pull up your personal history but I don't know how they could POSSIBLY find out all the things they able to find out about you otherwise.
I do know that the Department of Homeland Security spends an enormous amount of time, money, and resources tracking the trucking industry. They are convinced that terrorists would like to use trucks to attack our cities and landmarks. I'd have to say that they are probably correct. It makes perfect sense.
So if you are trying to hide in any way from any law enforcement agency you should probably stay far away from the idea of getting your CDL. For the rest of you, come on in.
The point of all of of this is to inform you that no matter how legal and untouchable you may THINK you are by having your truck all shined up and your logbook caught up with hours of driving still available I promise you it's an illusion.
You are only free to roam this country in a big rig as a commercial driver because they are allowing you to do so. You do not have the right as a commercial driver to be left alone no matter how perfect having that right may seem. They can shut you down, search your vehicle, and hold you in custody if they really want to or feel they need to.
Now I'm not saying you're likely to be thrown in prison for life for absolutely no reason. I'm simply saying please don't make the mistake of copping an attitude or making a dumb decision based on the facade that you have some God given rights and nobody can take them away from you.
That may indeed turn out to be a big mistake someday.