Toyota held onto its dominant position in annual vehicle quality rankings, which were revamped to highlight design and layout problems that can irritate consumers as much as defects.

Toyota and Lexus, the automaker’s luxury brand, took the top spot in 11 out of 19 vehicle categories in the survey released Wednesday by J.D. Power and Associates. Porsche AG came in first in the overall ranking of brands, averaging 91 problems per 100 vehicles. That compared with an industry average of 124 problems per 100 vehicles.

The study, in its 20th year, was revised to isolate consumers’ concerns about design flaws, as distinct from defects and malfunctions. The change in methodology makes year-to-year comparisons impossible.

However, a parallel survey conducted using the old methodology found that as a whole, the industry improved 8 percent from 2005, said Joe Ivers, executive director of quality and customer satisfaction research at J.D. Power.

Lexus came in second in the overall nameplate rankings, with 93 problems per 100 vehicles, while the Toyota brand was fourth with 106. The two brands scored particularly well on the defect side of the equation.

"They’re the closest thing to defect-free," Ivers said Toyota and Lexus.

On the other hand, Porsche’s top ranking had a lot to do with good design: It had the least number of design problems of any brand, but was behind Lexus when it came to defects and malfunctions.

The design issues that tended to irk people most were those having to do with ergonomics and the integration of technology into a vehicle, Ivers said.

A prime example was BMW AG’s BMW brand, which had an average of 142 problems per 100 vehicles. It ranked among the best for defects and malfunctions, but took a beating from survey respondents in the design area. In particular, Ivers cited BMW’s iDrive system, through which many different controls are operated by a single knob.

Bob Lutz, vice chairman for global product development of General Motors Corp., criticized "systems where you gather everything under one control and then you are asked to scroll through menu after menu trying to do things.

"We are used to having certain vehicle controls in certain places," Lutz said Wednesday at an auto interiors show in Detroit prior to the release of the J.D. Power results.

BMW spokesman Dave Buchko defended iDrive, saying customers expect cutting-edge technology from the brand.

"New stuff is new," he said. "It takes a bit of time to gain some familiarity with it."

But Ivers argued it is possible to integrate new technology in a way that doesn’t make a vehicle less user-friendly. "Porsche has all the functions but none of the complaints," he said.

Even Toyota and Lexus could improve when it comes to technology and ease of use. Jim Lentz, group vice president for Toyota’s U.S. sales division, said some complaints focused on use of the handsfree system for cell phones and even the clocks in vehicles.

In vehicle segments, Toyota had five winners, including the Corolla for compact car, the Camry for midsize car, and the Sequoia for large sport utility vehicle. Lexus had six top vehicles, including the IS 250 and IS 350 for entry premium car, the SC 430 for premium sporty car and LX 470 for large premium SUV.

Of the Big Three domestic automakers, General Motors made the strongest showing. Its vehicles won in two segments: large pickup (Chevrolet Silverado LD) and large car (Pontiac Grand Prix).

DaimlerChrysler AG’s Chrysler Group had a hit with the Chrysler Town & Country, which was the top-ranked van. Ford Motor Co. also won a segment with the Ford Ranger for midsize pickup.

Hyundai Motor Co. scored a sleeper hit with consumers, with the Hyundai brand coming in No. 3 with an average 102 problems. The Hyundai Tucson took the top spot for compact SUV or crossover.

J.D. Power, based in Westlake Village, Calif., collected responses from 63,607 purchasers and lessees of new 2006 model-year vehicles after 90 days of ownership for the study. This year’s survey included 217 questions, up from 135 in previous years.