Average gas prices topped 99 cents per gallon.

The national average price of a gallon of gasoline has creeped up to more than 99 cents and could top the $1 mark if demand rises during the summer vacation driving season, said Trilby Lundberg, publisher of the Lundberg Letter, a newsletter that tracks the oil industry. A nationwide survey completed Friday of 13,000 gasoline stations combining all three fuel grades showed the average gallon price nationwide rose .38 cents from 98.7 to about 99.1 cents since the last survey two weeks ago, Whether the average price tops $1 “will depend on millions of decisions yet to come on the part of vacationers and other travelers,” Lundberg said.