In 2014 I did an organised 30 day trip through Ethiopia. Our itinerary in this region was: Kombolcha - Awash and the next day from Awash to Harar.
From Kombolcha (or Dessie) you travel around 4-6 hours on a gravel road before reaching the main Djibouti road. This is a good asphalt road. Our guid mentioned that in this area Lucy was found, but it is almost impossible to visit this site itself as there is no infrastructure between Kombolcha and Awash. You start very early and arrive at dark in Awash.