NEW YORK (CNNMoney.com) -- Americans took 10.3 billion trips on public transportation last year, marking the highest ridership level since 1957, according to a new study.

The rate of ridership continued to climb at a quarterly rate of 3.3% through the first three months of 2008 to 2.6 billion, according to research from the American Public Transportation Association (APTA). That's nearly 85 million more trips than the same period last year, the APTA said.

"There's no doubt that the high gas prices are motivating people to change their travel behavior," said APTA president William Millar, in a statement.

The number of riders on trolleys and streetcars rose 10.3% in the first quarter of 2008, while the number of commuter rail riders grew 5.7%, according to APTA data. Ridership on subways, elevated trains and buses also increased.

"People are looking at the gas prices and they're making a choice," said Joe Calderone, spokesman for the Long Island Rail Road (LIRR), a commuter rail system in Long Island, New York.

The LIRR, which recently hiked fares, has seen ridership increase 5.4% during the first 4 months of 2008, compared with the same period a year ago.

Last year the LIRR served 86.1 million riders, the most since 1949, according to Calderone.

The average price of gasoline nationwide crossed the $4 a gallon mark last Sunday, and the price of regular gasoline is now over $4 a gallon in more than half of the states in the country, according to a daily survey from automobile group AAA.

In a survey released last month by IBM's Institute for Electronic Government, a total of 31% of commuters who normally drive to work said they would change their transportation habits if gas were to cross $4 a gallon.

IBM also found that a total of 66% of drivers would seek other means of transportation if gas hits $5 a gallon.