High gasoline prices and a slowing economy mean less traffic in Honolulu and across the nation, according to a traffic congestion study released yesterday.

However, Honolulu's traffic congestion remained the worst in the country, according to the annual report by INRIX, with Los Angeles in second place.

Honolulu's travel time index, which is a ratio of peak period travel time to free flow travel time, dropped from 1.47 in 2007 to 1.36 this year, according to the report. That means, for example, that a trip that took 29.4 minutes last year now takes 27.2 minutes.

INRIX, a company based in Kirkland, Wash., compiles traffic information nationwide. Its National Traffic Scorecard is based on an analysis of traffic patterns during the first half of 2008 and survey of 2,000 consumers in October.

Survey respondents of all income levels said they've reduced their driving. However, those making less than $35,000 were most likely to have decreased their driving.

Two-thirds of consumers surveyed said they took fewer driving trips, took shorter trips, carpooled or used public transportation more because of higher gas prices.

The reductions came amid rapidly rising gasoline prices. The average price for self-serve regular gasoline in Honolulu rose from a little more than $3 a gallon in November to nearly $4.40 this summer, according to the AAA Daily Fuel Gauge Report. Prices have since backed off to about $3.63 a gallon for regular yesterday.

That spike in prices should have a lasting impact on driving behavior, said Bryan Mistele, INRIX founder and chief executive.

"Although we can't predict the future price of fuel, we can predict the potential impacts to traffic congestion," he said in a news release. "As a whole, the population appears to have made lasting changes to their behavior, which we expect to persist at some level even if gas prices revert to pre-2007 levels."

Nationwide, the INRIX survey said, U.S. commuters will spend an estimated 6.5 fewer hours driving to work this year because of reduced congestion.

"It's the biggest drop in traffic congestion since the oil crisis in the 1970s," said Scott Sedlik, INRIX's vice president of product marketing.

U.S. motorists drove less in July for a ninth consecutive month, the Federal Highway Administration said on Sept. 30. The annual total may fall for the first time since 1980.