The competition to develop vehicles with greater fuel efficiency has heated up in the face of ever-more-stringent government standards. But new government rules are also creating unexpected alliances. In a first for the auto industry, U.S. automaker Ford and Japanese behemoth Toyota have announced a partnership to create new gas-electric hybrid engines unlike anything available now. Here, a guide to this development:

What are Ford and Toyota working on?
Trucks and SUVs, primarily. New rules from the Obama administration require automakers to develop a fleet of vehicles averaging 54.5 miles per gallon by 2025. But the rules also incentivize manufacturers if they can make pickup trucks and SUVs — typically the biggest gas-guzzlers on the road — using more fuel-efficient hybrid drivetrains. Ford and Toyota will seek to do just that.

Aren't these two companies strange bedfellows?
Yes and no. Partnerships like this are increasingly common in the auto industry, and Ford makes the best-selling truck in the all-important American market (the F-150), while Toyota is recognized as the industry's leader in hybrid engine technologies. Though Ford and Toyota will remain competitors, their hybrid collaboration is expected to yield innovations faster and cheaper than if either automaker worked independently.

When will their hybrid innovations reach the market?
Not for several years. Earlier this week, the automakers inked a preliminary deal that's expected to become a more detailed formal agreement next year. Cost-sharing and the specifics of the deal, such as how many engineers from each company will be assigned to work on hybrid technologies, have yet to be determined. Nonetheless, considering the strength of the SUV and truck market in the United States, this is big news. "Common sense, it seems, has finally found its way to SUV and truck makers," says Martin LaMonica at CNET.

Sources: CNET, NY Times, Wall Street Journal