ROME — Ten dollars a gallon may seem unthinkable to American drivers still smarting from the spike in gas prices to around $4 a gallon. But that was nearly the price that Marco Annarumi faced recently when filling his Jeep on his way home from work.

"It hasn't changed my driving at all — not a bit — I just have to work harder," he said with seeming indifference.

High oil prices and high taxes on gas pushed the average price of gasoline to new heights in much of Europe this summer. Yet transportation experts in this laboratory of sky-high fuel prices say many Europeans, out of necessity, habit or love, have proved surprisingly willing to bear the extra cost of driving. That raises questions as to how effective high prices by themselves can be in achieving the ambitious targets for reducing carbon dioxide emissions that European leaders have committed themselves to meeting.

Gas prices have persuaded some people to drive less. Traffic on the Eurostar train that links London and Paris was up 21 percent in the first three months of 2008. Gas purchases in Italy dropped 10 percent compared with the year before. Sales of gas-guzzling sport utility vehicles have plunged across the continent, just as they have in the United States.

But, at least so far, there are few signs of the wholesale shift away from current driving habits that environmental economists contend is needed for European countries to meet emissions control targets. The U.N. Intergovernmental Panel on Climate Change says meeting the targets is crucial if the world is to prevent the worst effects of global warming. Rental car companies say their business is up this summer. Many consumers appear willing to economize in other parts of their lives — eliminating vacations, movies, even birthday gifts — before choosing not to drive.

"We do see reports of a significant change in the types of cars people are buying, but I've been mostly surprised at the lack of a reaction," said Peder Jensen, a transportation expert at the European Union's European Environment Agency in Copenhagen. "One had hoped that these prices would deter driving, but people have coped better than we hoped they would."

Although new car sales in both Europe and the United States have slumped this year, the number of cars per person has continued to rise, partly because many people now have more than one car, according to statistics from the Organization for Economic Cooperation and Development.

Partly because of high gas prices here, European cars are already far more efficient than those sold in the United States. The average new European car gets 40 miles to the gallon, double the average for new cars sold in the United States. Even so, total carbon emissions from all forms of transportation in Europe are rising. They are about a quarter higher today than they were 20 years ago, while emissions from industry have declined in the same period.