A bus of Boltbus in an undated file photo. Many Americans have abandoned their love of getting behind the wheel during the last year, and opted to hop on buses instead, according to a study released this week.

Many Americans have abandoned their love of getting behind the wheel during the last year, and opted to hop on buses instead, according to a study released this week.

Inter-city bus service jumped 9.8 percent between the fourth quarters of 2007 and 2008, the highest growth rate in more than 40 years.

"The growth in intercity bus traffic is being driven by a number of factors, chiefly the spiking price of fuel over the past year," said Joseph Schwieterman, professor of public service and director of the Chaddick Institute, who directed the study, released on Monday.

"The basic economic efficiencies of bus travel are proving to be extremely attractive in this difficult economic climate," he said.

The revival of downtown districts and a growing acceptance of bus travel among younger travelers are also partly responsible for the U.S. bus renaissance, the study found.

The study includes all arrivals and departures of all conventional intercity bus companies, such as Greyhound Lines and Continental Trailways, as well as curbside bus operators, but not commuter-bus operators.

Much of the growth was driven by two companies, Megabus and Boltbus, a joint venture of the Greyhound and Peter Pan bus companies, which started curbside pick-up service in northeastern states in spring 2007.

The two companies offer high-frequency service between major U.S. cities and wireless Internet service on board.

Growth in passengers choosing to take the bus has also had an environmental impact. Over the past year, bus route growth has reduced carbon dioxide emissions by an estimated 36,000 tons and 3.48 million gallons of fuel, according to the study.

The number of Americans who traveled by car dipped 3.3 percent in the first eight months of 2008.