Photo by Eric Keith / St. Joseph News-Press / Purchase this photo

The high cost of gasoline is beginning to curtail American driving habits.

Armchair economists once speculated that drivers in the Midwest would never tolerate $2 gas.

But people bought it.

When unleaded neared $3 per gallon, pump predictors decided that customers would cut down on their driving and buy less fuel.

People still bought it.

And with gas marching toward the $4 mark, people fill their tanks as much as ever.

Or do they?

Americans cut their driving in March by the largest margin ever recorded, according to the U.S. Department of Transportation. Compared with March 2007, drivers slashed their mileage by 4.3 percent — or 11 billion miles. The department’s Federal Highway Administration has tracked national driving statistics since 1942.

St. Joseph drivers admitted that they were surprised with the drop. Wayne Pierce said that despite his efforts to cut back on miles, he still has to fill up twice a week.

“A lot of people say they’re going to drive less, and I try, but you still have to drive to work and take the kids to school,” Mr. Pierce said. “I guess some people are better at it than me.”

If drivers stay stingy with their driving habits, gasoline supplies could increase, leading to a drop in prices. Crude oil traders drew a similar conclusion Tuesday. Light, sweet crude for July delivery dropped by more than $3 to $128.85 per barrel after reaching record-highs last week.

Some oil executives remain unconvinced that oil prices will decline. Texas tycoon T. Boone Pickens said last week that he expected $150 oil by the end of the summer.

Kerry Cordray, spokesman for the Missouri Department of Natural Resources, said it was too early to judge how much impact consumers could have on gas prices.

“It has been known to have effects in the past when we’ve had price run-ups with gasoline,” Mr. Cordray said. “It’s hard to look at the current situation and know how much impact it will have.”

Clinton Thomas can be reached

at clintonthomas@npgco.com.