By WILL LESTER 

.c The Associated Press

WASHINGTON (AP) - Three in 10 Americans say the rise in gasoline prices has affected their vacation plans this year - either by causing them to cancel trips, cut back their plans or change their mode of transportation, says an Associated Press poll.

The number of people who expect to take no vacation - 15 percent - has tripled since May 1999, and the number who will travel by car has dropped below half, according to the poll conducted for the AP by ICR of Media, Pa.

``Gas prices are not only affecting my vacation plans, but my everyday plans,'' said Mona Whorton, 38, of McCall, Idaho. ``We're going to take one vacation instead of two. We wanted to go to California this year, but we're not going to go.''

The poll suggested the biggest effect of the rise in gas prices was to cause people to cut back their vacation plans, 17 percent, while another 8 percent said it would cause them to change their type of transportation and 5 percent said they canceled vacation plans because of the increase in gas prices. Almost a fourth who plan to travel by car said they would be cutting back vacation plans.

``I'm going to cut back my vacation plans because of the prices,'' said Mike Durham, 47, of Richmond, Ind., who is married with three sons. ``I don't mean shorten the time, shorten how far I'm going to go. I'd planned to drive to northern Minnesota or Canada, but we'll probably will have to stay within 100 miles of home.''

Travel officials have predicted some cutbacks in travel plans as gas prices surged throughout the spring - with the price of regular unleaded gas increasing more than 16 cents a gallon in the past month to more than $1.70 per gallon on average nationwide. Gas prices were expected to peak over the Memorial Day holiday.

Officials with travel organizations like AAA say they don't expect the travel industry to go into a tailspin because of cutbacks and they note that alternative vacations like cruises have been getting a lot of interest.

Surveys by the travel industry have also reflected that concerns about rising gas prices could cause some people to cut back or cancel their travel plans.

The number of people traveling by car on their vacations dropped from 55 percent in May 1999 to 47 percent this year, according to the AP poll, with some of those people shifting to other modes of transportation or canceling vacations altogether. A third planned to travel by plane. The poll of 1,008 people was taken May 16 through Sunday and has an error margin of plus or minus 3 percentage points.

People who made more than $75,000 a year were most likely to travel by plane, with more than half saying they would fly on vacation. People who made less than $50,000 were more likely to drive than fly by a 2-1 margin.

About a third said they plan to spend less than $500, a slight increase from two years ago, and fewer than four in 10 said they would spend between $500 and $1,500, a slight drop from two years ago. About one in 10 said they would spend $3,000 or more.

Rodney Crozer, a 30-year-old lineman for Pacific Gas & Electric from Fresno, Calif., said changing his vacation plans ``never crossed my mind.'' Crozer plans to fly to Orlando, Fla., with his family, adding: ``My tickets were purchased a month ago.''

One in five said they expect to spend less on their vacation this year, double the number who felt that way two years ago.

Most people plan their longest vacation to last a week or less, with about half saying they would spend a week on their longest break and one in five saying less than a week.

People who don't plan on taking a vacation were most likely to be over age 65, make less than $25,000 and have less than a high school education. But the increase in the number who plan not to take a vacation compared with two years ago occurred in almost all groups.

Jerome Wentz, a 60-year-old farmer from North Dakota, said he's ``not going anywhere on vacation'' - a decision he made when gas prices started going up. ``It's affecting farming, too,'' he said.

Some were determined to take their vacations, even if they had to alter those plans.

``We plan on going to Florida,'' said Anna Jaudon, 48, a clerical worker from Dayton, Ohio. ``We were going to drive, but now we will take the bus.''

The rising gas prices are a consideration even ``when you decide you want to go for a ride,'' she said. ``We don't go shopping as much as we used to.''

AP-NY-05-24-01 0137EDT