Putting all-wheel-drive to a winter’s test: Do you need it?

American car consumers have an ever-increasing appetite for all-wheel-drive models that automakers, both domestic and import, are scrambling to provide. Data from R.L. Polk reveals that more than 20 percent of new car and utility vehicle retails sales in 2012 were all-wheel-drive models. Overall, retail sales of all-wheel-drive models in the U.S. are up 53 percent since 2009.

Once a mainstay offering from luxury makers such as Audi, whose entire range of vehicles are available with all-wheel-drive, other manufacturers are joining in. But does it provide enough advantage over front-wheel-drive to justify the cost?

To find out, I recently spent a cold February day testing three different all-wheel-drive Ford models -- the Escape, Explorer and Fusion -- at a test facility in Michigan’s Upper Peninsula, along with a standard front-wheel-drive Fusion. Among U.S. automakers, Ford offers its latest all-wheel-drive system on the widest variety of models, bolting it into the Edge, Escape, Explorer, Flex, Fusion and Taurus. Demand for all-wheel-drive is strong in the Northeast and Midwest regions, but Ford has seen significant growth in other areas of the United States.

“All-wheel drive acceptance continues to grow in the East and Great Lakes regions, as expected, but nationwide all-wheel-drive sales have grown, particularly in the Pacific Northwest over the past six years,” said Erich Merkle, Ford sales analyst.

First, a bit on just how all-wheel-drive works, and what makes it different from the four-wheel-drive setups in work trucks and larger SUVs. Most all-wheel-drive systems act like front-wheel-drive the majority of the time, powering the front axle only until there's a need for extra traction, at which point power can be shunted to the rear axle. In four-wheel-drive, all four wheels are locked together turning in unison. These systems, which can be switched on or off either manually or electronically, and are useful mostly in extreme conditions.

Ford’s system, like those offered from many others automakers, uses a sophisticated package of electronics that monitor wheel spin and slip. If activated, it can immediately send power to the other axle, or even to a single wheel with the most traction.

The all-wheel-drive system is coupled with the car’s electronic stability control to help keep the car traveling in the direction the driver intends. The system samples data some 60 timers per second, using information from 25 individual sensors measuring speed, lateral acceleration, steering wheel position and throttle input to decide whether to cut the throttle and/or apply individual brakes, all in an effort to keep the car on its intended path.