 By 1947 , US 395 ran concurrently along the portion of SR 78 from Vista to Escondido before continuing along Santa Fe Avenue to Bonsall and Fallbrook and rejoining its alignment during the 1970s . At this time , all of SR 78 that existed had been paved . Before the present @-@ day freeway was built , SR 78 was routed on the Vista Way Freeway ( which was an expressway ) from Oceanside east to downtown Vista . After this , it followed Santa Fe Avenue and Mission Road east ( now signed as CR S14 ) , continuing onto Grand Avenue in Escondido . Following the intersection with US 395 , SR 78 turned south on Ash Street and rejoined the current alignment of the highway . In 1949 , the rerouting of SR 78 from US 395 to US 99 was listed as a priority by local officials . The road was known for its curves , even though it went over relatively flat terrain ; this reduced its efficiency . 
