That doesn't necessarily mean there's a disagreement about safety between workers and supervisors, it could just as well mean they both disagree with the regula

That doesn't necessarily mean there's a disagreement about safety between workers and supervisors, it could just as well mean they both disagree with the regulators about the acceptable level of risk. This would make sense from first principles, because unsafe truckers impose externalities beyond the direct risks to truckers and their supervisors, by making the roads more dangerous to the public.