More than 24 million Americans - 11 percent of the adult population - are using buses, light rail, commuter rail and other forms of public transportation more than they did last year, according to a new nationwide survey commissioned by the HNTB Companies.

An even greater percentage of survey respondents, 16 percent, said they expect their ridership to increase in the coming year.

Nearly one in three Americans (32 percent) said their biggest motivator to choose public transportation over driving would be high gas prices. While conventional wisdom holds Americans would find it frustrating to give up the convenience of a car, the survey found the second most popular reason someone would choose public transportation rather than driving is more convenience (14 percent). Avoiding traffic (5 percent) was a distant third, followed by concern for the environment (4 percent).

"Our interstate highways are aging and under tremendous strain, and we're seeing the costs of an unbalanced transportation system," said Peter Gertler, vice president and national director of public transit services for HNTB Corporation. "Now more than ever we need to invest in multiple modes of transportation that address modern demands and preserve our quality of life."

Gertler cited several benefits in a balanced approach to transportation that includes public transit:

• Saves time and conserves fuel - 541 million hours and 340 million gallons, according to the Texas Transportation Institute's 2007 Urban Mobility Report.

• Saves money - Americans living in areas served by public transportation save $18 billion annually in congestion costs.

• Promotes cleaner air - Public transit usage reduces U.S. carbon emissions by 37 million metric tons a year, equivalent to the electricity used by 4.9 million households.

For additional survey information, go to www.hntb.com