Ann Freeman was filling up her Pontiac Vibe, watching the numbers on the pump spin so fast they blurred, when she noticed something she'd never seen before.

"I had never broken 40 bucks on gas before," she said, muttering to herself: "This is ridiculous."

She went home, got out her bicycle and took it in for a tuneup.

"My knees aren't what they used to be," Freeman, 54, said Monday afternoon. "But thanks to higher gas prices, I am motivated to drive less, ride more, save money and consume less."

As the average price of regular gasoline hit $3.88 a gallon Monday in the Twin Cities -- and threatened to enter the $4 orbit last reached in June 2008 -- Freeman wasn't the only one changing habits.

Buses are packed. Bike lanes are jammed. People are juggling child visitation dropoffs and making errand loops instead of separate trips to the vet, the cafe and the grocery store.

Steep gas prices are even affecting romance. Tom Marver of Mendota Heights said he changed his settings at dating service, limiting his radius to 25 miles instead of the 50-mile range over which he used to cast his net of potential love.

"The empirical evidence shows that escalating gas prices prompt people to cut back on driving and travel, work more from home and combine trips," said Prof. Akshay Rao, a marketing expert at the University of Minnesota's Carlson School of Management. "We are seeing a lot more sensitivity to energy consumption."

For five straight weeks, Americans have bought less gas than in comparable periods last year, according to MasterCard Spending Pulse, which monitors gas sold at 140,000 stations nationwide. The first week of April saw drivers pumping 2.4 million fewer gallons than they did last April -- a 3.6 percent drop despite an economic warmup that has created roughly 1 million jobs in the past year.

"More people are going to work and they should be buying more gas," said John Gamel, MasterCard's gas research director.

But more than two-thirds of major gas station chains reported lower sales in a March survey. In the Twin Cities, where the price of gas soared 30 cents this month, that drop is showing up in places large and small.

Parking ramps in downtown Minneapolis are seeing higher vacancy rates, said Dan McLaughlin, executive director of the Transportation Management Organization, which helps car-poolers find parking discounts. He said car-pool rates are up 30 percent and ramp owners are approaching him to fill vacant stalls.

First-quarter Metro Transit ridership numbers come out later this week, but spokesman John Siqveland said light-rail, train and bus ridership rose 1.5 percent in the first two months of 2011 compared with 2010. Visits to Metro Transit's website broke records last month, with 205,000 people clicking there 650,000 times -- despite a typical lag of a few weeks between spikes at the pump and increases in transit ridership.

Siqveland and others expect commuter behavior to mirror the summer of 2008, when gas cost $4 a gallon and surveys showed a 29 percent increase in bicycling and Metro Transit recorded all-time highs.

"The buses are really packed," said Laura Kittelson, who commutes from Chanhassen to her downtown Minneapolis accounting job. "I used to be able to park on the second floor of my park-and-ride ramp. Now they need overflow lots."

Errand loops

Steve Basile and his wife, Naomi Sack, used to make a few errand runs a week from their south Minneapolis home. Both own economy cars, but now Basile says they do "giant errand loops together on the weekend." Recently, that meant combining the dropoff of their dog at the vet for an annual checkup, a grocery run, visits to a book and thrift store, and lunch at a cafe -- all on the same outing.

"We sit there and plan it," Basile said. "It cuts our errand driving in half."

For Freeman, that recent $42 fill-up proved to be the boiling point. She used to commute by bike from the Seward neighborhood to her job at the University of Minnesota. She'd use her bike to visit friends, buy groceries and pick up prescriptions.

But then she raised two kids, dropping them off at different day-care centers.

Now a grandmother of two with somewhat creaky knees, Freeman says gas prices have motivated her to saddle up again. "That $40 tank," she said, "renewed my commitment to return to those good habits."

The Associated Press contributed to this report. Curt Brown • 612-673-4767