Drive times vary greatly
Drive times vary significantly in the Dominican Republic depending on current road conditions (construction), traffic levels, and weather (rain can bring things to a halt).
For example, it is about 4 hours from Santo Domingo to Puerto Plata. I've done it in just over 3, and I've also spent 2 hours just to get across Santo Domingo in heavy traffic, with a trip time of over 6 hours (raining).