SUMMARY: In response to a petition for rulemaking from the Alliance of Automobile Manufacturers@ NHTSA is issuing this final rule to facilitate the development and introduction of fuel cell vehicles@ a type of electric-powered vehicle@ and the next generation of hybrid and battery electric powered vehicles. It does so by revising the agency's standard regulating electrolyte spillage and electrical shock protection for electric-powered vehicles to align it more closely with the April 2005 version of the Society of Automotive Engineers (SAE) Recommended Practice for Electric and Hybrid Electric Vehicle Battery Systems Crash Integrity Testing (SAE J1766). The standard currently requires manufacturers to design their vehicles so that@ in the event of a crash@ a vehicle's propulsion battery system will be electrically isolated from the vehicle's electricity-conducting structure. As amended@ this rule provides greater flexibility@ requiring manufacturers to design their electrically powered vehicles so that@ in the event of a crash@ the electrical energy storage@ conversion@ and traction systems are either electrically isolated from the vehicle's chassis or their voltage is below specified levels considered safe from electric shock hazards. Since the physiological impacts of direct current (DC) are less than those of alternating current (AC)@ this rule specifies lower electrical isolation requirements for certain DC components than for AC components. The current standard does not recognize the difference in safety risk between DC and AC components@ requiring both types of components to meet the same requirements. As requested by the petitioners@ this final rule specifies the following electrical isolation requirements: 500 ohms/volt for AC and DC high voltage sources and 100 ohms/ volt for DC high voltage sources with continuous monitoring of electrical isolation.