In the 1970s, planning continued for the construction of the route, as well as modifications to the existing roadway. The City of La Mesa began discussions regarding adding SR 125 from SR 94 to I-8 into the scenic highway system in 1968; the county Planning Commission continued pursuing these plans in 1970. SR 125 was lengthened by the Legislature to extend to the Mexican border in 1972. In 1973, then-governor Ronald Reagan vetoed a bill to delete part of SR 125 from state plans, over concerns that not enough transportation studies had been done on the matter. An improved interchange with SR 94 was being planned the next year. Soon after, Caltrans raised concerns about the remainder of SR 125 not being constructed, due to objections from the community relating to freeway construction in general.