Horton (or was it WC?) had this flip-up traffic advisor with inlaid LED's. Not huge, but it was actually somewhat effective.
Taylor Goodman
Captain - Henrico County (VA) Division of Fire
Fire Chief - Huguenot VFD, Powhatan, VA
Captain - Henrico County (VA) Division of Fire
Fire Chief - Huguenot VFD, Powhatan, VA