When asked how to get between Boise and Mountain Home on a bicycle without riding on I-84 and without riding the Old Oregon Trail, which is dirt road, I haven’t been able to give a good answer. Until now.
From Bike Touring News to the eastern most exit off of I-84 it is 14 miles. Take Federal Way south past Gowen Road to Memory Lane and turn right to the freeway Exit 59B. Actually, this route does mean about 8 or nine miles on the freeway, but the shoulder is wide and smooth and rumble strips divide it from the traffic. Ride to Exit 71 Mayfield Road. Turn left across the freeway to Desert Wind Road. Turn right and follow Desert Wind as it becomes W. Tilli Road. Turn right on Ditto Creek Road which crosses I-84 to the junction with Old Oregon Trail Highway. Turn left and parallel the freeway into Mountain Home. This is not the most scenic route in the world, but it will get you to Mountain Home and from there Old Highway 30 takes you to points East.