Abstract: A highway sign machine adapted to be mounted in an overhead position proximate to a traffic lane operates under local or remote control to dis play selectively to motorists any of a plurality of written traffic messages on a vertical sign face covering the front profile of the machine and virtually duplicating the appearance of standard overhead signs for expressways that continuously display unchanging messages. A plurality of traffic messages are written longitudinally on angularly spaced message faces on rotors that are rotatably indexed to different message presenting positions where the rotors are accurately located and releasably held by rotary cam and follower means against vibration. Replaceable message panels on the rotors are supported by lightweight structure resistant to bending and vibration and comprising extruded corner chords having tubular bodies and integral flanges connected by diagonal webs underlying the message panels.