I would only interpret adverse conditions to include traffic accidents, road impediments by labour strife, terrorism, criminal investigations, and weather related road closures or other acts of god as they are unpredictable. Anything that is predictable or is possible to have forewarned knowledge of such as rush hour traffic, announced construction delays, even coming storms while considered acts of god, if they have been announced, they are generally considered plan able to avoid and I think you would have a hard time beating a ticket given for it. Even an undue delay at a shipper or consignee that would have otherwise allowed you to beat rush hour I doubt you could get away with because even if it is legit, it would be a huge loophole that everyone would be using all the time to extend their driving time so legit or not, it can't be an allowable excuse.
also any adverse condition that allows you to extend your driving time must be given back immediately the next day so it cannot extend your 70 hour week.