Final answer:
In poor visibility on a highway, the safest course of action is to pull over and wait for visibility to improve. Using high beams can worsen visibility in fog, and driving slowly with hazards on is risky.
Step-by-step explanation:
When driving on a highway and visibility becomes so poor that you can barely see, the safest action to take is to pull over and wait for visibility to improve. Speeding up would increase the risk of an accident, using high beams can actually worsen visibility in fog by reflecting off the water particles, and continuing to drive slowly with hazard lights on could still lead to a collision if other drivers are not able to see you in time.
It is crucial to ensure that when you pull over, you do so in a manner that maximizes your safety and the safety of other road users. Find the farthest point away from the travel lanes, turn on your hazard lights to alert other drivers, and wait until you can see clearly before re-entering the road. Patience and caution are key in such low visibility conditions on the highway.