In a year when Detroit launched a comeback, the real news in the automotive world came from Washington, D.C. In July 2011, President Barack Obama announced a historic agreement with 13 automakers to increase fuel economy to 54.5 miles per gallon for cars and light duty trucks by model year 2025. The agreement meant little to consumers looking for cars in 2011, but it meant a great deal to the engineers designing next-generation vehicles.

During the course of the year, mainly in anticipation of such declarations, automakers around the globe launched new technologies aimed at helping them reach the aggressive fuel economy goals. They rolled out plans for hybrids, plug-in hybrids, and electric cars. They announced motor-generators for mild hybrids. At the same time, they also unveiled technologies aimed at helping with safety and vehicle connectivity.

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Here's a look at the five biggest trends.

1) Vehicle electrification: In what may be the biggest news for electric cars in the past decade, the Chevy Volt and Nissan Leaf hit the streets in 2011. Sales numbers have been small -- 8,048 for the Leaf and 5,003 for the Volt through October -- but manufacturers of both vehicles promise those numbers will rise. The Volt and Leaf weren't the only electric cars to make headlines, however.

At the Detroit Auto Show in January, Ford announced plans for the Focus Electric. GM also shook up the automotive world later in the year by announcing its first all-electric car since the ill-fated EV1. Called the Spark EV, it will begin production in 2013. Luxury automaker BMW said it would also roll out an all-electric production vehicle known as the i3 in 2013. Other electrifications include the jumbo-sized 102EX concept car from Rolls Royce and the DeLorean EV, an electric car that marries existing vintage-1980s DeLoreans with a lithium-ion-powered electric drivetrain of today.