The typical direction is from Paia to Hana.
The disadvantage of this route can be that the side of the road used is more crowded than others. However, it is not correct to say that you "escape the traffic" if you take the route from Hana to Paia.
On the contrary, if you drive the route in this direction (from Hana to Paia), along the many hairpin curves on the way there and back, you will encounter many more vehicles that you will have to avoid. Driving in narrow passages is thus made more difficult and the traffic risk increases.
Another disadvantage of driving the route "the other way around" is that you are on the side facing the ocean. In order to get to the sights, it is often necessary to change sides of the road in heavy oncoming traffic.
Our recommendation is therefore to choose the typical route and to "go with the flow" from Paia to Hana in a relaxed way. The way is the goal!
However, a real tip to avoid some traffic on the way there is to choose your departure time as early as possible and, in case of doubt, plan stops like Paia and Ho'okipa Beach Park for another vacation day. (Or end the evening there after the return trip).