Abstract: A light bar incorporates an extruded base and top panel where the top panel is supported above the base by two ruggedly constructed electronics enclosures. The base top panel and electronics enclosures form a structure to which various light units, lenses and covers are attached to form the finished light bar. The top panel is one of the last components to be installed, leaving the internal components of the light bar accessible during assembly. Each electronics enclosure may surround a power supply that includes a heat-generating component, such as a power transistor. Each enclosure is provided with an opening through which the heat-generating component protrudes to form a heat transfer interface with a heat sink plate mounted to the outside of the enclosure. A further heat transfer interface is formed between the heat sink plate and the top panel in the assembled light bar.