June Hill Robertson McCarroll ( June 30 1867 â '' March 30 1954 ) was a nurse ( later a physician ) with the Southern Pacific Railroad in the early twentieth century . She has been credited by Caltrans with the idea of using a painted line to separate lanes of traffic on a highway . June Hill Robertson McCarroll ( June 30 , 1867 â '' March 30 , 1954 ) was a nurse ( later a physician ) with the Southern Pacific Railroad in the early twentieth century who is credited by Caltrans with the simple but revolutionary idea of delineating highways with a painted line to separate lanes of traffic .