The Obama administration is nearing completion of a major federal regulation of greenhouse gas emissions for the first time in U.S. history. The Environmental Protection Agency and Department of Transportation will jointly issue a rule regulating vehicle emissions by mandating increases in fuel efficiency over the coming years.

Tuesday, EPA and DOT’s National Highway Traffic Safety Administration submitted a draft final rule for review by the White House Office of Information and Regulatory Affairs (OIRA), the last step in the rulemaking process before publication. The rule must be published by April 1 in order to give automakers enough time to comply with the rule’s requirements for model year 2012 vehicles.

In the proposed rule, EPA estimated the standards would reduce climate changing greenhouse gas emissions by 950 million metric tons and 1.8 billion barrels of oil for cars sold in the model years covered (2012-2016).

The environmental gains aren’t the only benefits worth noting; drivers’ budgets will benefit too. Under the proposed rule, DOT estimated fuel cost savings of more than $150 billion.

The joint rules have the support of both environmentalists and the auto industry who came to an agreement in May 2009. Environmentalists persuaded the administration to use California’s vehicle emissions program, which had never been implemented, as a model for the federal regulations. Even though automakers had objected to the California plan, they signed on because they wanted one standard applied to all 50 states.