Due to lack of use after 1869, most of the wagon roads across the Sierra were allowed to deteriorate until, by the early 20th century, many were again next to impassable to wagons. The railroad served nearly all trans-Sierra passenger and freight needs. The arrival of the automobile in the early 20th century revived the need for good Sierra roads. By 1910, only the Placerville route (now a state highway) was maintained well enough for car and truck traffic to get over the Sierra. The Truckee Trail that was modified and upgraded to the Dutch Flat and Donner Wagon Road over Donner summit had deteriorated so badly that the road had to be extensively rebuilt and relocated to become passable for cars or trucks. After extensive upgrades and modifications this road would become U.S. Route 40 and later Interstate 80.