General Motors and Toyota captured 15 of the 18 top model segment awards, according to the J.D. Power and Associates 2005 Initial Quality Study (IQS) released on Wednesday.

In the study, Toyota Motor Corporation earned 10 of the top model segment awards, with the Lexus SC 430 honored as the highest-ranking model for the second consecutive year, at 54 problems per 100 vehicles (PP100). Other Toyota models earning segment awards include the Toyota Prius (Compact Car), Scion tC (Sporty Car) and Toyota RAV4 (Entry SUV).

General Motors earned five top model segment awards, including those for the Chevrolet Malibu/Malibu Maxx (Entry Midsize Car), Buick Century (Premium Midsize Car) and Chevrolet Suburban (Full-Size SUV).

HUMMER improved dramatically, with a 36 percent reduction in reported problems. Since its debut in the 2003 IQS, HUMMER has reduced reported problems by 115 PP100.

Ford Motor Company captured two model awards, with the Ford Explorer Sport Trac (Midsize Pickup) and Ford F-150 LD (Full-Size Pickup) ranking highest in their respective segments.

The Chrysler Group maintained the quality levels of its products. The Chrysler Group's score of 125 was unchanged from last year. Overall DaimlerChrysler vehicle quality (including Mercedes-Benz and smart) improved one point to 122.

Nissan performed dramatically better in the 2005 study, with the Nissan Quest as the most-improved model, recording an impressive 104 PP100 improvement.

Other models showing notable improvements are the Kia Spectra (64 PP100 improvement), the HUMMER H2 (63 PP100 improvement), and the Scion xA (62 PP100 improvement).

Overall, the automotive industry garners only a minor increase in industry-wide initial quality in 2005. After showing an 11 percent quality improvement from 2003 to 2004, the overall industry average has improved only one PP100 in 2005 to 118 PP100.

Among the nine problem categories surveyed, ride/handling/braking and exterior problems continue to cause the greatest challenge to manufacturers. Consumers report that the transmission causes the least number of problems.

IQS is a model-level study. It measures 135 attributes across nine categories, including ride/handling/braking, engine and transmission, and a broad range of quality problems symptoms reported by vehicle owners. Survey results in chart form.