BOSTON -- Massachusetts police and fire departments are getting squeezed hard this summer as they struggle to keep patrol cars and fire engines on the streets, despite skyrocketing gasoline and diesel costs and fixed budgets.

From one end of the commonwealth to the other, departments are trying to figure out ways to conserve on fuel without compromising on public safety.

"Letting cars idle is not a good idea," said Methuen Police Chief Kathi Lavigne, who said she's instituted several measures to try to cut fuel costs.

Lavigne said she's reduced the number of cars officers can take home and has asked officers to avoid letting cruisers idle while they're on patrol calls.

Many agencies rely heavily on gas-guzzling vehicles, but they must perform their essential duties whatever the cost of fuel.

Fixed annual budgets for gas and fuel, however, have not kept up with steeply rising prices, leaving some departments struggling to stay out of the red.

“The cost of gas is way too high for us,” said Lavigne.

Lavigne said her department had a budget of about $150,000 for oil and gasoline - including diesel -- in the 2008 fiscal year, which closed at the end of June. She said the 88-man department, which serves a population of 50,000, ended up spending $15,000 per month.

Other police departments are in similar, or even worse, situations.

The Worcester Police Department had a 2008 fiscal year gas budget of $465,000, but spent $674,000. The extra $209,000 ended up coming from other city funds, said Worcester Police Sgt. Kerry Hazelhurst.

The Worcester department’s deficit occurred despite adjustments made over the last few years.

“In five years, we tripled our budget just in gasoline,” Hazelhurst said.

Compounding the problem for some departments is the fact that their most recent budgets, for the 2009 fiscal year, were not increased from the year before but were level funded.

In Edgartown, on Martha’s Vineyard, where gas is especially expensive because of the cost of getting it to the island, the police department was given a $29,000 gas budget for both 2008 and 2009, said Chief Paul Condlin.

The department has eight cruisers and used about 11,000 gallons of gas last year, Condlin said.

Right now, he said, gas on the island is priced at about $4.85 a gallon, but his department gets a break from the federal gas tax and a discount from the dealer. Even so, that still means paying $4.52 per gallon which adds up to close to $50,000 a year to cover the town's 26 square miles during the busy summer season, when its population jumps from 4,000 year-round residents to about 35,000.

While departments are doing what they can to conserve gas, and to avoid a budget deficit at year’s end, keeping the public safe doesn’t necessarily lend itself to frugality.

The operation of patrol cars poses one of the biggest difficulties for departments trying to conserve.

Throughout the Bay State, departments have been trying to decrease unnecessary vehicle use as much as possible.

“We try to limit our idle time,” said Hazelhurst.

In some places, such as Weymouth, the message on vehicle use has come from the local government. There, the mayor issued a “no idling order,” said Robert O’Connor, of the Weymouth Department of Public Works.

While placing restrictions on idling has been one of the most widespread attempts in the state to save gas and money, it is a strategy that isn’t always viable for daily police work.

Patrol officers don’t use their cars only for transportation, but also for a variety of purposes over the course of their daily shifts. Keeping the engine running often is necessary for an officer’s job.

“The patrol car not only is the office for the officer on the street, but it’s also a temporary shelter for the victim of a crime, or others,” Fitchburg Police Sgt. Glenn Fossa said.

Condlin made a similar point. “Idling at an accident scene would occur,” he said, because it is necessary to run the computer in the patrol car.

It makes the implementation of cost-saving strategies very tough.

"There's not a lot, that I can see right now, without affecting how we operate and manage," he said.

Apart from changing officers’ habits, some departments have followed the trend among consumers by trying a move to smaller, more gas-efficient cars.

The shift hasn’t met great success because larger vehicles were found to be necessary for many of the rigors of police work.

“Smaller cars didn’t hold up for patrol,” said Captain Timothy Carr of the Weymouth Police. “To stand up to the beatings [cruisers] take, you need a stronger car.”

Carr did say smaller cars have been more appropriate for administrative purposes, and that his chief has downsized his vehicle.

Like the Weymouth Police, the Fitchburg department also maintains a fleet of smaller vehicles for administrative and ancillary duties, said Fossa.

"Over time, there's been many public safety departments using more fuel-efficient vehicles, but that's a long-term strategy," said Jeff Beckwith of the Massachusetts Municipal Association.

Short of trading existing vehicles for smaller, gas-saving models, departments are trying less drastic changes to save money.

Fitchburg and Needham police have begun to use LEDs for their cruisers’ light bars. The bright displays are made up of small bulbs that don’t use as much energy or draw as much gas as traditional incandescent lights.

“The smaller drain from better technology saves gas,” said Fossa. Over the course of a year, he said, the savings add up.

In a further effort to take advantage of technology, Fitchburg Police Chief Robert DeMoura has led an initiative to bring in Segway Personal Transporters to the department.

“There seems to be a tremendous momentum from city leaders to obtain these,” Fossa said.

He also said the Fitchburg department may look into leasing a couple of motorcycles.

Mentioning an even more traditional two-wheeled gas-saver, Fossa noted that “bicycle patrols have been popular the last few years.”