This document will cover the aspects of the design and test of Class 4 through 8 electric and hybrid-electric trucks and buses for electrical safety. The document is intended to address the safety concerns of electrical systems in commercial vehicles that employ voltages greater than 60 VDC or 30 VAC RMS. Hybrid Electric powertrain technology has been newly introduced to the commercial Class 4 through 8 truck and bus market. With this introduction, hybrid trucks and buses now contain components with higher voltages and stored potential energy. The presence of high voltage batteries, motors, and electronics therefore creates new potential electrical hazards that were not before present on non-hybrid trucks and buses. The safer operation of trucks and buses is a shared priority of all truck and bus operators, fleet owners, OEMs, and suppliers and is not a basis for competition. Therefore, the SAE Truck and Bus Council formed the Truck and Bus Hybrid Safety committee. The committee members have volunteered to develop common, consistent design and test practices that can be applied to hybrid technology for Class 4 through 8 vehicles, in order to benefit the drivers, maintainers, and emergency personnel who come in contact with these vehicles. Although specifications for hybrid electric technology have been developed and published for passenger cars, specifications have yet to be adopted for Class 4 through 8 vehicles. This recommended practice is intended to leverage the existing body of SAE hybrid standards, and to also leverage procedures already developed individually by truck and bus industry manufacturers for the safer operation and service of their vehicles. The focus of this document will be the documentation of practices for those aspects of hybrid technology that relate uniquely to Class 4 through 8 trucks and buses.