Changeable Message Sign. Traffic control devices capable of displaying one or more alternative messages, changeable manually, by remote control, or by automatic control. TRIMARC message signs are dynamic message signs. Variable message signs are matrix signs with eight or more characters per line capable of displaying a very large variety of messages. Variable and/or dynamic CMSs are typically used on freeway and expressway mainlines. Both variable and/or dynamic CMSs can be fixed at a location, portable, or truck-mounted. TRIMARC primarily uses fixed message signs that are capable of displaying 2 frames, with 3 lines of up to 26 characters. TRIMARC also has several smaller portable VMS's used for special events or long term incidents.