The North American International Auto Show opened on Monday with fresh signs the comeback by U.S. carmakers is gaining traction.

In the first big event of the show, the Chevy Volt, the centerpiece of General Motors' return from bankruptcy and already the winner of both Motor Trend Magazine's car of the year and Green Car of the Year awards, was named 2011 North American Car of the Year award, beating out rival vehicles from Japan's Nissan Motor Co Ltd and Korea's Hyundai Motor Co.

The latest version of Ford Motor Co's Explorer sport utility vehicle, meanwhile, was named 2011 North American Truck of the Year -- the third year in a row that Ford has dominated the category.

The U.S. sweep of the awards, which are voted by a panel of 49 automotive journalists, provided an encouraging auto show kickoff for Detroit's Big 3 automakers. The show is the first in a string of trade events where automakers clamor to build buzz for vehicles months before they hit showrooms.

The Volt, it really represents the soul or the essence of the new General Motors, Tom Stephens, GM's vice chairman for global product operations, said as he accepted the award.

The award, Stephens said, was a recognition of the the creativity, the perseverance and the dedication of thousands of employees which continued even during GM's darkest days.

The U.S. auto industry snapped a four-year sales decline in 2010, including three consecutive sales months above the 12 million unit annual rate to close the year. Most analysts expect double-digit growth in 2011 and further gains in 2012.

The last time the U.S. auto market saw three consecutive years of substantial sales growth was in the late 1990s when Detroit automakers were still riding high.

James Paulsen, chief investment strategist for Wells Capital Management, believes U.S. sales could reach annualized rates of 15 million to 16 million units by the end of 2011.

Other analysts have offered a more conservative outlook on 2011, given persistently high U.S. unemployment rates and a still-uncertain outlook for the housing market.

Jeff Schuster, director of forecasting for J.D. Power and Associates, expects U.S. auto sales to reach 12.8 million vehicles in 2011 and rise to 15 million in 2012.

The 2011 forecast could increase, he added.

I think coming off the momentum we had in the fourth quarter there's more likely to be upside risk than a downward revision, Schuster said at a Society of Automotive Analysts meeting in Detroit on Sunday.

HAPPY DAYS ARE HERE AGAIN, ALMOST

If austerity was the watchword at the Detroit auto show for the past three years, then growth and new investment aimed at capitalizing on the still-developing upswing dominate presentations this year.

One sign of the industry's renewed confidence: vehicle debuts are expected to roughly double at the Detroit auto show this year to as many as 40 all-new vehicles, up from 18 in 2010.

Another major theme: the rollout of new small cars, electric vehicles and hybrids that major automakers have readied at a time when oil prices -- and gasoline prices at the pump -- are heading higher.

Those include a larger version of Toyota's market-leading Prius hybrid, the first-ever compact sedan for General Motors' Buick and a boxy concept known as the Curb from Hyundai.

The Korean automaker grew at more than twice the rate of the overall market in 2010 at 24 percent, seizing market share from rivals with competitive pricing and a reputation for sharply better quality.

The Detroit auto show also represents a major milestone for Volkswagen. The German automaker plans to show off a new version of its Passat that will be built at its first U.S. plant since the 1980s. The $1 billion plant in Chattanooga, Tennessee, is near completion and will begin operations later this year.

The Detroit show is also significant for the U.S. automakers, which are in varying stages of a comeback in sales and in profitability.

GM completed its public share offering in November, the largest ever, and its shares are up 18 percent from the IPO price. Chrysler is expected to launch its own IPO in the second half of 2011.

GM shares were flat at $38.98 on Monday morning while Ford shares were down 3 cents at $18.24.

Ford passed Toyota as the No. 2 U.S. automaker in sales behind GM in 2010 and its stock has risen more than 80 percent since the start of last year.

Ford posted a 19 percent U.S. sales gain in 2010, its largest percentage increase since 1984.

A KPMG survey found a much higher percentage of senior automotive industry executives expects global market share growth from Ford than Toyota in 2011.

Ford in one year essentially eclipsed Toyota, which is a big change in one year, said Gary Silberg, who leads KPMG's auto consulting business in the United States.

After massive recalls and U.S. market share losses in 2010, Toyota aims to turn the tide by expanding its Prius hybrid into a family of vehicles in a bid to enhance consumer perceptions that the automaker is a leader in green technology.

(Reporting by David Bailey; Additional reporting by Kevin Krolicki, Bernie Woodall, Deepa Seetharaman, James Kelleher and Chang-Ran Kim in Detroit, and John Crawley in Washington; editing by Matthew Lewis)