(b)(1) Any vehicle utilizing an auxiliary power or idle reduction technology unit in order to promote reduction of fuel use and emissions because of engine idling shall be allowed an additional 400 pounds total to the gross, axle, tandem, or bridge formula weight limits defined in this section.(2) To be eligible for the exception provided in this subsection, the operator of the vehicle must provide written proof or certification of the weight of the auxiliary power unit (APU) and demonstrate or certify the idle reduction technology is fully functional at all times.(3) Written proof or certification of the weight of the APU must be available to law enforcement officers if the vehicle is found in violation of applicable weight laws. The weight allowed cannot exceed 400 pounds or the actual weight proven or certified, whichever is less.(4) It is the intent of this subsection to apply at the state highway level the weight limit increase for vehicles using a functioning auxiliary power or idle reduction technology as provided in the Federal Energy Policy Act of 2005."