A comprehensive research effort to develop operator's manuals for variable message signs (VMSs) was undertaken to improve the operations of both portable and permanent (fixed-site) VMSs in Virginia. This report describes the development of two manuals, the Permanent VMS Operator's Manual and the Portable VMS Operator's Manual which will be published separately. These manuals were based on information obtained from the literature, VMS operators, and motorists. Issues addressed by the manuals include when a VMS should be used, where a portable VMS should be placed, and the design of the VMS message. The manuals are not simply a list of pre-defined messages. They are a series of concise modules guiding the operator through the thought process required to use a VMS effectively. The operator follows a logical decision tree from module to module, to achieve the best placement and best message for a VMS. Effective VMS use actually requires a complex thought process, despite the apparent simplicity of the messages. The manuals include essential material about VMS operation. Based on theoretical calculations and motorists' experiences, it is strongly recommended that a VMS use no more than two message screens. A single message screen is preferred. VMSs should be used only to advise drivers of changed traffic conditions and convey specific traffic information concisely. Due to limited information capabilities, VMSs should be used in conjunction with other means of communication such as highway advisory radio and static signs. Most importantly, it is crucial that credibility be maintained. Incorrect information can have extreme consequences in terms of VMS effectiveness.