When truckers know there is a weigh up position ahead, they will get into the right lane to be ready to exit. If they have a transponder in their truck for a pre-clearance check (PrePass, Best Pass, Green Light or Norpass), they might not exit, but they’ll get in the right lane until their transponder give them “the green light.” Sometimes the weighing scales is stopped and the truckers don’t have to exit the freeway.
But when truckers don’t know there is a weigh up position ahead, they may get caught out in the left lane. If they are transient slower moving vehicles (most likely other truckers who have slowed down in preparation to exit to the weigh station), they may have to do a few tricky driving to get over into the right lane in time. Or they may miss the exit overall and pull over on the shoulder of the freeway. These truck scales walk into the scale house with their official procedure in hand and their heads hanging low.
You can blame the trucker for not being ready in those instances, but what about bench scales that have been closed down for a while? What about new weigh up station or scales houses that aren’t marked properly on the trucker atlas? Truckers want to be ready but occasionally there are factors that at truck driver just can’t control.