Engineering trends at the NAIAS the tech behind the searchlights - North American International Auto Show 2003

Automotive Industries, Dec, 2002 by Dan McCosh

Still, this year, at least, alternative drive systems are in a kind of limbo. The real business at hand is light trucks.

* Platform shift

It's no great surprise that America's fascination with all the permutations of light trucks continues. But like the disoriented drum major running to get ahead of his marching band, those working to improve this basic genre sometimes find it a struggle to set trends rather than follow them. The so-called "crossover" vehicles--labeled as trucks but evolving from car and minivan platforms--continue to proliferate, and may well become the dominant family vehicle type in the near future.

The NAIAS will see continued proliferation of crossovers. The Cadillac SRX, the Infiniti FX45 and the Mitsubishi Endeavor will get their official launch. The Porsche Cayenne and Volkswagen Touareg push the envelope in the luxury arena. These follow the 2003 introduction of new crossovers from Honda, Nissan and Subaru--making crossovers the most popular new category.

While the glut of crossovers tends to give the impression that the day of the conventional SUV is over, this ignores the fact that last year was the tail end of the major changes at GM and Ford in their mainstream SUVs. Truck-based SUVs still dominate the marketplace Buick wit the launching the few new traditional, full-frame SUVs debuting there.

The crossover trend is driven partly by an interest in improving handling, interior environment, and fuel economy of traditional truck-based SUVs. It's also motivated by the impact of CAFE standards on advanced product planning. If a vehicle crosses over from the car to the truck category--a decision under the aegis of the National Highway Traffic Administration (NHSA)--it tends to improve the truck fleet CAFE, typically burdened by full-size SUVs. At the same time moving a 4WD vehicle with relatively poor fuel economy, at least by car standards, out of the car CAFE category helps that problem as well.

But fuel economy is hardly the main driving force to this shift in thinking. The short list of the benefits of a truck-based, full-frame SUV includes its inherent ruggedness, important in-trailer towing and serious load carrying. The crossovers are characterized by uni-bodies and a drivetrain that at least starts out as front-wheel drive. This basic architecture frees up a lot of real estate for features such as third-row seats that fold invisibly into the floor. It also lowers step-in height even when high ground clearance is maintained. Most have FWD-derived drive systems that improve straight-line stability in slippery conditions, while 4WD adds transitory traction, used mainly to get unstuck.

* Right side up

In short, from the engineer's point of view, crossovers seem to offer a significant improvement over conventional SUVs, while shifting the basic design emphasis from the woods to the mall.

Along with the shift to lower, uni-body ersatz SUVs comes a new emphasis on traction and stability. Much of this has come from new derivatives of basic traction-control systems, where the full-brake control implicit in antilock brakes that also are capable of generating positive pressure is applied to single wheels. Yaw control was the first generation, when single-wheel braking helped control the onset of a skid. The new Volvo XC90 carried this another step, by intervening in a rollover with a stab at a single-wheel brake, timed to break the roll harmonic. Ford's Explorer also will get the system.