Neb. Rev. Stat. § 60-6,364

Sections 60-6,363 to 60-6,374 shall apply to all diesel-powered motor vehicles operated within this state with the exception of the following: (1) Emergency vehicles operated by federal, state, and local governmental authorities; (2) Vehicles which are not required to be registered in accordance with the Motor Vehicle Registration Act; (3) Vehicles used for research and development which have been approved by the Director of Water, Energy, and Environment; (4) Vehicles being operated while undergoing maintenance; (5) Vehicles operated under emergency conditions; (6) Vehicles being operated in the course of training programs which have been approved by the director; and (7) Other vehicles expressly exempted by the director.