Over the river and to the gas station

Grandma lives in Paso Robles. Cousin Jim moved to Turlock. And the stepkids are in Petaluma.

No way around it: If you want to see the extended family this Christmas, you'll probably have to drive – just like every other year. In fact, Christmas is traditionally ranked as the third-busiest travel holiday, after Thanksgiving and the Fourth of July, according to the American Automobile Association.

But in these cash-strapped times, as families work harder at managing their budgets, climbing gas prices have been known to put the squeeze on holiday travel plans.

"I'm always concerned about it," said Kathleen, a rushed local gas shopper who declined to give her last name, "I don't travel unless I have to."

So at what point do higher gas prices begin to affect holiday travel?

"I don't think there's necessarily a specific number," said Matt Skryjal, a spokesperson for AAA's Northern California region. But be added that when it comes to price-per-gallon, there does seem to be a "psychological tipping point."

"It depends on who you talk to," he said. "If you were to talk to investors and analysts, they would tell you that four dollars is a tipping point."

Skryjal agreed that "Something does happen at the four-dollar mark psychologically," but noted that there are multiple factors involved. Above all, he said, "It depends on people's individual budget."

If $4 per gallon is an important marker, Gilroy residents should be in the clear this year. As of Dec. 7, the average price in that region for a gallon of regular unleaded was $3.25, according to Fuel Gauge Report, a AAA-run website which monitors fuel prices on a daily, weekly, monthly and yearly basis.

Prices seemed to vary widely around that average. For example, on the same day at Rotten Robbie on Leavesley Road, the price per gallon was only $3.13. At Hecker Pass Shopping Center on First Street, it was $3.27.

"At $3.50, $4, you start to see a lot less people," said Maria Quintaña, who has seen prices jump as high as $5 since she started working at the station three years ago.

Skryjal said gas prices are driven largely by oil investors, the strength of the U.S. dollar, and geopolitical factors. "On average," he added, "California prices are 25 cents (per gallon) more than the national average" due to state taxes and special environmental requirements.

Regionally within the state, he said, prices are "driven by localized markets." San Francisco, Eureka and South Lake Tahoe typically have among the highest prices.

AAA regularly releases predictions on travel numbers in advance of the holidays. A report for the upcoming Christmas holiday is due out on Dec. 17.