 The San Diego Chamber of Commerce and the San Diego Highway Development Association urged for the conversion of SR 78 west of Vista , a length of 5 @.@ 6 miles ( 9 @.@ 0 km ) , from an expressway to a freeway in April 1967 . The College Boulevard diamond interchange on this western segment was scheduled to open to traffic on October 24 , 1967 , and connected the recently relocated MiraCosta College to the freeway . The interchange , previously an at @-@ grade intersection , improved traffic flow to the college by removing the left turn across the highway needed to access it . The construction of the interchange cost $ 800 @,@ 941 ( about $ 10 @.@ 3 million in 2015 dollars ) . May 1968 saw the state designating the Jefferson Street and Emerald Drive interchanges as a priority . In August 1968 , the state allocated $ 750 @,@ 000 ( about $ 8 @.@ 91 million in 2015 dollars ) for building the Jefferson Street interchange . Further funding difficulties were encountered due to US 395 being given priority , but both interchanges had funding by August 1970 . 
