One risk in product development is to underplay design heritage. In many product venues, from haute couture to automobiles, customers cheer the reiteration of classic design cues. They want to enjoy them again. For an easy lesson on how the pros approach retro design, snoop around the next auto show. You'll discover that some cars of the future, as Yogi Berra put it, are "dj vu all over again." For example, when Ford Motor Co. displayed the 2002 Thunderbird at last January's North American International Auto Show in Detroit, it was clear that the company was hoping to relive a past success -- the enthusiastic customer acceptance of the original two seater of 1955. That classic T-Bird was a sell-out and there is no mistaking the design cues borrowed for the new iteration. In effect, Ford successfully test-marketed the design back in 1955 and is now simply attracting nostalgia buffs as well as young buyers who just appreciate good design. The new T-Bird is not the first retro success for Ford's J Mays, vice president for design. His previous retro achievement was at Volkswagen where he collaborated with Freeman Thomas on the new Beetle. It's natural to assume that going retro means borrowing from your own corporate past -- as in another Mays example, the Ford Forty-Nine show car. Recent show goers were immediately able to connect the two-door to the 1949 original just by looking at the slab sides and fender skirts. The rest of the vehicle represents a different kind of retro-authenticity. Because the original 1949 Ford was often customized by second or third owners, Ford stylists took inspiration from their typical efforts to lower, repaint, rechrome and chop and channel the vehicle. In some instances inspiration for retro designs seems to spring from an industry's collective past. For example, consider Ford's introduction of fender integrated headlights on the highly streamlined 1936 Lincoln Zephyr. The integrated headlamp theme was retro in the sense that it was a styling feature introduced years earlier by Pierce-Arrow and Chrysler's Airflow designs. The feature was available on the Pierce-Arrow as early as 1914 and on the Airflow beginning in 1934. More recent retro styling themes also seem to evoke ambiguous origins. For example, Chrysler's successful PT Cruiser melds design cues common to many automakers of the 1930s. In going retro, note that a wide variety of artistic freedom is successfully practiced. That even includes how a product is categorized. Chrysler's PT Cruiser, which would have been considered a car in the 1930s, is now said to be somewhere in the truck-derived SUV/crossover categories. Actually the PT Cruiser is a fortuitous exploitation of the current Neon chassis. Sometimes scientific developments empower a retro effect. One example is how the Autonomy show car from General Motors Corp. would reinvent an earlier ownership experience. The use of fuel cells and drive-by-wire technology will give Autonomy owners of the future a simple, practical ability to switch bodies. In the 1920s and 1930s luxury car buyers had to go to custom body shops and endure months of waiting for the new body to be executed. With the Automony, owners would only have to find a dealer who stocks the desired new body. Is your industry sector as old as automaking? Rejoice because you have more to be retro about! The longer the product history, the greater the opportunities to revive and combine tried and true product features to serve the customer preferences better. Done right, retro enhances brand loyalty by letting customers once more enjoy the timelessness of classic design efforts in otherwise updated products. Think of your best efforts as art or classical music that customers hope to enjoy again. John Teresko is an IW senior technology editor. He is based in Cleveland.