Hawai'i drivers should get relief from soaring gasoline prices next week when the weekly adjustment to the state's wholesale gasoline price cap is expected to drive down pump prices by about 50 cents a gallon.

The price cap was launched Sept. 1, and since then, gasoline prices have taken Hawai'i drivers on a roller-coaster ride, with the pump price for a gallon of regular rising to about $4 a gallon on Maui yesterday.

On O'ahu, where drivers have seen pump prices rise 80 cents for a gallon of regular in just two weeks, prices could fall to around $3.10 a gallon next week as the price cap forces wholesale gasoline prices down about 50 cents to around $2.98 a gallon, including taxes, according to Advertiser calculations. Retailers typically tack on an average 12-cent-per-gallon markup.

The state Public Utilities Commission will announce the revised cap today to go into effect on Monday.

In a separate development yesterday, Shell Oil said it is seeking to repeal the nation's only gasoline price control law via the courts.

Shell Oil has asked for a Hawai'i Supreme Court review of the PUC's decision to implement the caps over objections raised by oil companies and state consultants. Shell is challenging the PUC's implementation process and not the substance of the law itself.

"Shell has complied with the law and will continue to do so," the company said in an e-mail. "At the same time, the company is going to work within the law to get the price cap repealed. The Hawai'i consumer is now being subjected to a misguided economic experiment."

Shell filed its request with the PUC, which forwards it to the state Supreme Court, said Kevin Katsura, legal counsel for the PUC.

Before the state's wholesale gasoline cap law, such volatility was unheard of in Hawai'i, where prices historically have been high but stable. The caps change that by tying Hawai'i prices to prices in Los Angeles, the Gulf Coast and New York on a lagging basis. Hawai'i prices spiked sharply this week in response to a rise in Mainland prices caused by supply disruptions from Hurricane Katrina.

Hawai'i prices are expected to fall next week by a similar amount because of a fall in Mainland prices last week.

"Welcome to Mainland-type prices," said Jack Suyderhoud, a business economics professor at the University of Hawai'i-Manoa. "These kinds of swings will occur. It shouldn't come as a surprise that this is happening."

Proponents of the Democrat-backed law contend consumers will ultimately benefit from lower prices by having pump prices correlate to Mainland price swings.

"The good news is the parity with the Mainland prices will help to alleviate prices" next week, said House Majority Leader Marcus Oshiro, D-39th (Wahiawa). "We've consistently said give the law time to work."

Critics contend the law will make Hawai'i prices higher and more volatile and could result in supply disruptions if oil companies decide to close or leave the state.

Because the law caps only wholesale prices, lower street prices won't occur next week unless gasoline stations pass along savings to consumers. Local dealers this week said they would.

"We're hoping the worst is over," said Barney Robinson, who operates Chevron stations near Honolulu International Airport and in Kahala, where the price for regular jumped 44 cents a gallon to $3.699 this week. "This is not something that we're pleased about.

"We're trying real hard to stay competitive and keep the price low to the consumer."

Honolulu pump prices neared $3.70 a gallon in many locations yesterday. On the Neighbor Islands the lowest regular gasoline prices available yesterday were $3.969 a gallon in Wailuku, Maui, and $3.819 a gallon in Lihu'e, Kaua'i.

Kaua'i officials said high gas prices appear to be pushing drivers from their cars to the county bus system.

County transportation executive Janine Rapozo said her office has received calls from people asking about bus schedules, so they can work the bus into their own schedules. Within the past two weeks, bus ridership is up about 5 percent, she said.

Kaua'i County fuel costs are up about 50 percent over the level at which budgets were estimated, and the county is beginning to look for ways to economize as well as for programs that can be raided for gas money, said Mayor Bryan Baptiste.

"We're going to have to do a money bill in order to keep up with the gas prices," Baptiste said.

Despite this week's spike in prices, Gov. Linda Lingle said, she's not ready to suspend the caps. Lingle, who opposes the caps, has the power to suspend the law, but has said she would do so only if the law has an adverse impact on the economy, public health, or the welfare and safety of the state's residents.

Meanwhile, one local business yesterday said it is taking steps to offset higher gasoline costs faced by employees. Pacific LightNet Communications said it is giving its 100 or so employees $50 a month extra to help defray high gasoline costs. The company also is offering employees free bus passes.

"We're doing this for our employees," said Pat Bustamante, president for Pacific LightNet. "It's the right thing to do."

Reach Sean Hao at shao@honoluluadvertiser.com.