IWSenior Technology Editor John Teresko presents a review of three "concept cars" unveiled this week at the Detroit Auto Show: Chrysler Panel Concept Truck A year ago Chrysler unveiled the PT Cruiser, a retro design that some say takes the best advantage of how cars were more efficiently and attractively "packaged" during the 1930s and early 1940s. (Taller, but no longer than a small car, its interior volume rivals that of a full-size sedan, Chrysler says.) At this year's show, the automaker reinterpreted the design as a panel concept truck. "As we prepare to launch the all-new Chrysler PT Cruiser [in the spring], we wanted to have a little fun and show what design directions we would take," says Tom Gale, executive vice president for product development and design. In addition to the Panel Cruiser (shown), Gale's crew also prototyped a GT Cruiser with a 200bhp, 225 lb-ft turbocharged engine under the hood. The Mercedes-Benz Vision SLA Out of the Mercedes Technology Center in Sindelfingen, Germany, comes the Vision SLA, a sexy roadster concept that symbolizes pure driving pleasure. It builds upon the company's 1.9 liter engine (125 hp) from the Mercedes-Benz A 190 and adds such innovative touches such as aluminum for the load-bearing parts of the body plus high-quality plastic for the outer bodyshell. The lightweight construction (total weight: 950 kilograms) moves quickly on 19 in. wheels. Other modern touches abound in the lighting systems -- light emitting diodes (LEDs) at the rear and xenon projection headlamps up front. Since the projection technology operates without reflectors, the xenon lamps and projection lenses can be housed in aesthetic aluminum cylinders with a diameter of just 50 millimeters. The company's A-Class also serves as the model for the concept car's safety features. For example, in the event of a serious head-on collision, the oblique positioning of the drive unit ensures that -- as with the A-Class -- it slides below the vehicle, leaving the interior largely undamaged. Seat belt tensioners, belt force limiters, and airbags offer occupants additional protection. Volkswagen's Advanced Activity Concept (AAC) Combining all the functions of a pick-up with the luxury of a top-class sedan, the AAC couples full-time, four-wheel drive to a 313-hp V10 diesel engine via a six-speed automatic transmission. (A Tiptronic manual shift mode is included.) In tough off-road situations, an extra-low ratio and two differential locks are just a push button away. Ground clearance can be varied by 4.33 in. via the vehicle's three-position air suspension system. Is the vehicle scheduled for production? Volkswagen will only say the concept vehicle signals the kind of changes that could take place in this model category within a very short time.