THE PRICE of oil - up to a record $146 a barrel as I write, has sent shock waves through the U.S. economy.

The most obvious sign is at the local gas station, where prices are well over $4 a gallon and still climbing. Gas has gone from an incidental in the family budget to a major expense, and the hardships are real - like for the single mom who lives nowhere near public transportation and drives her old gas-guzzler 25 miles round-trip to her job at Wal-Mart.

Taxi drivers now have to pay more just to do their job. Suburban parents who shlep their kids and their sports equipment to away games and tournaments in their SUV now find it costs almost $100 to fill the tank.

Nor are city folk immune. Even those who don't drive have found that higher fuel costs for truckers and manufacturers have led to higher prices for consumer goods, including basic necessities such as food.

No doubt about it, there's a lot of bad news. But as the cliché has it, every cloud has a silver lining.

The high price of gasoline has done what years of dire warnings have failed to do - get Americans to change their driving habits.

Air and water pollution? Global warming? Sending our dollars to unfriendly countries and corrupt regimes? That wasn't enough to get our attention. Now that the money is coming out of our pockets, Americans are doing what environmentalists and others have been urging for years: saving energy.

The gas crisis has generated a fundamental shift in attitude. A friend recently told me she used to do errands whenever she thought of them. "Now I combine them, and map them all out so I don't drive extra miles," she said. "And I walk whenever I can. I've made it part of my exercise routine."

More cars have their windows open and the air-conditioning off, despite the heat. People are carpooling to work and school. College students who live off campus are enrolling in online classes to save on the commute. GM has stopped making the once wildly popular Hummers.

A guy on a bicycle was recently spotted in King of Prussia wearing a T-shirt that read, "Can't Afford Gas."

Indeed, "Soaring gas prices are driving some motorists to try bicycles instead," PennDOT spokeswoman Jenny Robinson confirmed.

"The agency's official mission is to reduce traffic congestion. But we don't have control over drivers' behavior," Robinson added. "Market forces are effectively accomplishing that." PennDot itself has only recently started an internal ride-share board for its employees.

SEPTA ridership is up 5 percent from a year ago, with Regional Rail up 11 percent. "Those are highs we have not experienced for 25 years," said SEPTA's Felipe Suarez. Most of that growth, he said, can be attributed to gas prices.

In 2004, when my husband turned in his Lexus for a Toyota Prius, friends thought he was crazy. Now they think he was prescient - he gets more than 40 mpg! People are lining up to buy hybrid cars. Even NASCAR Sprint Club Champion Jimmie Johnson drives one.

For decades, Detroit made big cars, arguing that people wanted them. Now they can't get rid of them. The automakers lobbied unsuccessfully to stop recent legislation that would have raised automobile fuel efficiency standards and lowered emissions.

We need to seize the momentum for change and invest more in public transit and the development of alternative forms of energy. Reward American innovation, not consumption.

Fewer cars. Less driving. Less time spent in traffic. Greater fuel efficiency. It all adds up to cleaner air and water, and better health for people and the planet. Quite a silver lining. *

Deborah Leavy is a regular contributor to the op-ed page and an associate member of the Daily News editorial board. E-mail her at