Battery powered warning lights had taken over the highway construction industry by then. Now some warning lights are solar powered. See the link to the torch section of the traffic gard page for a brief description written by the late George Vandercook on why kerosene lanterns and torches ceased to be used. Safety was the primary reason that the use of open flame torches was discontinued. Speaking as a highway engineer, the MUTCD is still the standard used by the Federal Highway Administration to regulate all highway agencies in the United States.