Even with a scrappage rate (the number of cars taken off the road every year) estimated between 70 percent and 80 percent of new car registrations, the Hawai'i sales figures for 2004 mean that there could be an additional 24,000 to 36,000 cars on Hawai'i roads by the end of this year.

With private auto and rental sales both expected to hit record numbers, planners and drivers alike are wondering if there's room for all the new vehicles.

"I don't know where you'll put them. It's very, very crowded and seems to get worse each time we come," said Janet Shibuya, who visits Hawai'i regularly along with her husband. "We were warned about driving at rush hour, but it seems lunch time was just as bad. It's just as bad as where we live in San Francisco."

With more than 1 million vehicles already registered in the state, thousands of new cars arrive from the Mainland and Asia every week:

• Hawai'i auto dealers estimate they'll sell a record 68,890 new cars and trucks by the end of this year.

Janet and Kenji Shibuya rented a car during their stay in Hawai'i. Janet says traffic is just as bad here as in her home town, San Francisco. Bruce Asato • The Honolulu Advertiser

• And thousands more vehicles, new and used, are brought in by private individuals, including military families transferred to the Islands.

"The figure I'm hearing is maybe 120,000 or 130,000 new cars this year," said state Transportation Director Rod Haraga. "That's good news for the economy, but we're going to pay a price for it on the roads. If we don't start taking some precautionary measures, it's going to keep getting worse."

In public meetings across the state, Haraga has been warning residents about the need to find alternatives or risk even greater traffic problems in the future.

"It would be foolish to bury our heads in the sand," he said. "We've got to get people thinking about alternatives like car pooling or mass transit. We can't just build more highways. It's something we've got to get a handle on."

The trend doesn't appear to be slowing.

Matson Navigation, which shipped more than 140,000 cars into and out of the state in 2003, recently expanded its capacity to ship vehicles between Hawai'i and the Mainland.

Meanwhile a new company, Pasha Hawai'i Transport Lines, said work is nearing completion on the first of its two new $70 million roll on/roll off auto-carrying ships, each capable of holding more than 4,000 vehicles. The company expects to begin operations in Hawai'i early next year.

Even Hawai'i auto dealers are starting to worry about the implications of all those cars on the road.

"The essence of having a car is the freedom it affords you to move around, so there's starting to be some recognition that we have to push for measures that will keep that available in Hawai'i," said Dave Rolf, executive director of the Hawai'i Auto Dealers Association.

Last year, Hawai'i had the largest increase in new car registrations in the nation, up more than 17 percent over 2002. New car registrations in more than 30 other states declined during the same period, and Nevada was the only other state with a double-digit increase.

Rolf said dealers have begun discussing support for initiatives, ranging from more road improvements to alternate transit, that will keep highways safe and open as the number of cars continues to expand.

One little understood factor in the traffic congestion equation is the number of tourists driving in Hawai'i at any time, traffic planners said.

"No one really knows," said University of Hawai'i civil engineering professor Panos Prevedouros. "We don't have any way of counting them separately, but we know they are around and we know they represent a significant number."

A drop in tourism after 9/11 may have contributed to a decline in the state's traffic congestion index in 2002, as reported in one national study, Prevedouros said.

However, with tourism on the climb again, the congestion is likely to increase by the time the 2003 figures from the Texas Transportation Institute are released next fall, he said.

Hawai'i drew 6.35 million visitors in 2003, and more than half of them reported using a rental car during at least part of their time in the Islands, according to figures compiled by the Hawai'i Tourism Authority. U.S. visitors like to drive the most, with 77.3 percent using a rental car. By contrast, only about 21 percent of Japanese visitors used a rental car in 2003.

"Traffic does seem worse since when I was here four years ago," said Ieti Matatia, who was turning in his rental car at Honolulu International Airport last week and preparing to board a flight home to American Samoa. "I hope there will be some more highways by the time I come back again."

However, Justin Calkins, a visitor from Seattle, said he won't even bother with a car next time.

"We rented a car but never used it for the whole week," he said. "We took one look at the traffic out there and decided not to deal with it. Basically, we spent $300 for what amounted to a taxi ride to Waikiki."

Not every one was bothered by Honolulu's traffic; it depends where you live.

"Hey, I'm from Los Angeles and it's a heck of a lot better here," said Eric Nelson, who has been visiting the state for more than 20 years. Prevedouros said the state should consider hiring a tourism transportation coordinator, as many areas with large tourist populations have done.

"Every time there is a new idea out there, you have to think of the implications for private drivers, tour companies, and visitors," he said. "Seems to me there should be some formal procedure to consult with all those folks before changes are made."