Abstract: A tip up light bar assembly includes front and rear light bars pivotally supported above transversely opposed end assemblies joined by connector bars to form a rigid support structure. Each light bar is built on a rigid substrate having a uniform cross section. Longitudinally extending features of the rigid substrate provide locations for mounting light sources, electronic assemblies and lenses which, together with gaskets, define a weather-resistant enclosure surrounding the light sources and electronic assemblies. The light bars pivot at transversely opposed ends to a vertical position in which the light sources are elevated above traffic. Each end assembly includes a base plate, a pivotally mounted pivot plate. A gas spring reduces the dead weight of the light bar while a limit strap controls angular movement of the light bar relative to the base plate to approximately 90°. A motor-drive actuator exerts outward force on the pivot plates to move the light bars between a horizontal and vertical position.