Boosted by an improving economy and lower gasoline prices, travel is increasing on U.S. highways and transit systems, although individual American drivers appear to be driving fewer miles than they used to.

The rebound in vehicle traffic in 2014 followed six years of declining or stagnant numbers, attributed to tough economic times and changing driving habits.

Mass transit ridership also grew last year, continuing a decades-long trend.

Transportation patterns are being closely watched by policymakers and federal legislators as they debate ways to pay for highway and transit construction and maintenance.

Funding for the nation's Highway Trust Fund, which uses money generated by the federal gas tax to pay for highways and mass transit projects, will run out May 31, unless Congress acts.

Christopher Puchalsky, deputy director of transportation planning for the Delaware Valley Regional Planning Commission, said several factors had contributed to the rise in traffic.

"The biggest thing is lower gas prices," he said. He speculated that drivers were making more discretionary trips because gas is more affordable.

Also, as confidence in the economy recovers, consumers are more willing and able to spend on driving, Puchalsky said. And commercial traffic is increasing as the economy improves.

Nationwide, total vehicle miles traveled through November 2014 rose 1.4 percent to the highest level since 2007, before the Great Recession began, according to data collected by the Federal Highway Administration.

Vehicle miles traveled per licensed driver rose by a smaller amount, 0.86 percent, to 14,040 vehicle miles a year, and remained below pre-recession levels.

In 2007, vehicle miles traveled per licensed driver stood at 14,770.

Some of the decline can be attributed to changing driving habits among younger Americans, transportation experts say.

Young people are getting driver's licenses later or not at all. More of them are urban dwellers who opt to take the train or bus or bike to work, or telecommute. If they need a car, they can rent one by the hour, or summon a ride-share vehicle, such as Uber.

Mass transit continues to enjoy a resurgence in ridership, at 50-year highs. Through September 2014, the nation's transit agencies reported a 0.91 percent increase in passenger trips over the same period a year earlier, on pace to be the highest since 1956.

Amtrak is on track for another record ridership year: Total number of passengers was up 1.2 percent in the four months ended in January, and Northeast regional trains carried 1.8 percent more passengers.

In the Philadelphia region, SEPTA said Regional Rail ridership was up 2.8 percent through the first seven months of its fiscal year, with suburban bus service up 2.5 percent and city bus and subway service down 0.6 percent.

Ridership on PATCO, the 14-mile commuter rail line between Center City and South Jersey, declined 5.08 percent in 2014 after steady growth for most of the last decade. The drop was blamed on an ongoing track reconstruction project on the Benjamin Franklin Bridge, which caused delays and crowded trains.

Vehicle traffic was also down on toll bridges over the Delaware River.

The four bridges operated by the Delaware River Port Authority (the Franklin, Walt Whitman, Commodore Barry, and Betsy Ross spans) reported 47.8 million vehicles, a drop of 0.10 percent, a seventh consecutive annual decline. The record year was 2007, when 55.1 million vehicles crossed the bridges.

Traffic was down 2.2 percent at two toll bridges operated by the Burlington County Bridge Commission.

Both agencies blamed construction and bad weather for much of the drop-off in traffic last year.

The region's toll roads generally reported growing traffic in 2014, but the number of vehicles remained below pre-recession levels.

The Pennsylvania Turnpike counted 1.7 percent more vehicles in the seven months ended in December, compared to the same period in 2013. Still, there were fewer vehicles than in 2008.

The New Jersey Turnpike, which opened additional lanes to traffic in 2014, showed an increase of 2.9 percent, to 212.4 million vehicles. In 2007, the turnpike carried 251.6 million vehicles.

pnussbaum@phillynews.com

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