They weigh up at a paid scale at the flying J truck stop then use an electronic pass for the rest of the weigh stations along the way. That’s my guess anyways since I saw the paid scales at the truck stops being used. And I have seen that “something-pass” brand readers along the highway. I’m not a trucker. The state weigh station on my work commute is open and they chase trucks down that don’t stop. https://prepass.com/services/weigh-station-bypass-service/