The travel books said that the Road to Hana trip would be bumper to bumper. We did not experience alot of traffic but you should start out very early so that you can return before dark. You do not want to drive that road in the dark. The road is very challenging and you will want to stop along the way to see various waterfalls, beaches, towns, etc. My husband and I really enjoyed the trip. Our kids needed dramamine and my one daughter thought the day was a complete waste of time because she would have rather spent the day in the pool rather than in the car.
We stopped in Hana for lunch. It was very expensive but unless you pack a lunch, you are stuck. We stopped to body surf on the black sand beach of Waianapanapa State Park. It seems that all of the state parks in Hawaii have adequate shower and bathroom facilities. We ended up at Oheo Gulch expecting to swim in the 7 pools of fresh water. However, the pools were closed to swimming. The views there, as with the entire drive, were spectacular. We found out later that the day before, some drunk Hawaiian native accidently killed himself diving into one of the pools so perhaps that is why the pools were closed that day.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.