Trucks skipping weigh stations

Solved a mystery while traveling recently. For a year or two I had noticed some trucks skipping the weigh stations. This mystified me as I couldn't imagine the risk was worth taking if they were supposed to pull in and were just blowing it off. I hadn't seen anything to explain it, till:

We were heading toward Memphis from KY and at the weigh station approaches we saw signs that said something like "prepass rigs follow instructions in cab." Just remembered to look it up, and turns out it is a transponder arrangement. It appears to be based the belief that certain outfits are trustworthy, rather than pre-inspection . Or it may be a 'less frequent weighing' arrangement at random, that doesnt seem to be clear. Sorry if everybody already knew this.

http://prepass.com/
https://en.wikipedia.org/wiki/PrePass

The trucks are no longer required to actually enter the scales and if they do enter often can keep rolling rather than stop.

If they were weighed and found to be empty they get a signal to just go on by. Or weighed and found legal... go on by, neither weight nor duty hours having significantly changed. Some firms don't have electronic logbooks indicating driver's rest breaks, some do.

Been going on for a long time, especially
with the big haulers that own thousands
of trucks.

Saw the "obey in-cab signals" a few times on trips. Didn't completely know what it was for. But it makes sense. Enhance inspections at the terminals for the big guys, they are less likely to cheat anyways.