how does lexus ensure the high quality of every lexus vehicle
By placing an emphasis on targeting specific vehicle development standards.
Lexus
Lexus design has traditionally placed an emphasis on targeting specific vehicle development standards. 
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Lexus [SEP] Design and technology
Lexus design has traditionally placed an emphasis on targeting specific vehicle development standards. Since the marque's inception, design targets have ranged from aerodynamics and ride quality to interior ergonomics. The backronym "IDEAL" ("Impressive, Dynamic, Elegant, Advanced, and Lasting") is used in the development process. Each vehicle is designed according to approximately 500 specific product standards, known as "Lexus Musts," on criteria such as leather seat stitching. Design elements from the marque's concept vehicle line, the LF series (including the 2003 LF-S and 2004 LF-C), have been incorporated in production models. Vehicle cabins have incorporated electroluminescent Optitron gauges, SmartAccess, a smart key entry and startup system, and multimedia features.