HELENA, Mont. - In big, wide-open Montana, a state trooper might have to drive more than 100 miles to answer an emergency call, and routinely puts several hundred miles on the odometer in a day.

With gasoline at $4 a gallon, all that driving is tearing up the Highway Patrol's budget.

It is the same story elsewhere around the country, especially in big, sparsely populated Western states with vast stretches of highway. State police agencies nationwide are scrambling to reduce gasoline use and find the money to cover their costs. Some are beginning to worry that they will have to cut back on hiring officers.

North Dakota is not facing such a dire prospect, though gas prices are having an impact, the state Highway Patrol says.

"The state and the Legislature actually provided us with a budget that anticipated some higher fuel costs," said Capt. Dave Kleppe, the patrol's support services commander. The budget for the state patrol vehicles is about $4.5 million for the 2007-09 biennium, he said.

"We were actually under budget for the first half of the biennium. We're expecting to be over budget the second half, but we've got enough controls in place that we feel we'll be OK," Kleppe said Wednesday.

Ninety-four of the 141 patrol vehicles are Ford Crown Victorias, and the patrol may look at more fuel-efficient vehicles, he said.

Maj. Neil Johnson, the patrol's administrative services commander, said the patrol has not restricted travel, but has reminded officers to share rides to meetings take other steps to avoid wasting fuel. "Common sense mostly has done the job," he said.

For the Highway Patrol in Montana - the fourth-largest state in area, at 147,000 square miles - the options are limited. It is considered buying more V6 Chevrolet Impala cruisers to save gasoline, but initial tests showed the Impalas get about the same mileage as the department's V8 Ford Crown Victorias.

The Highway Patrol is over budget more than $340,000 in gas costs alone. To help cover its expenses, the agency has had to dip into its personnel budget.