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.

A former airfield turned test track offered a variety of different options to test the effectiveness of the traction systems in adverse conditions, with nothing more than a big snow bank to hit in case we pushed the vehicles too hard. Loose snow, packed snow and solid ice that would make a hockey rink proud were all part of the test track, as well as mixed-traction surfaces to fully demonstrate the system’s abilities.

Ford engineers were also touting two other features: Torque Vectoring Control and Curve Control.

Torque Vectoring Control splits the power between the two front drive wheels, increasing traction and agility when on the power and turning at the same time. The system allows for better grip and handling and makes novice drivers feel more in control.

With Curve Control, sensors in the vehicle check 100 times per second whether or not the vehicle is turning as quickly as the driver intends. If a driver enters a curve too fast and dials in more steering in order to make the turn – a.k.a understeer -- the system will reduce engine power and engage the brakes to reduce speed in order to complete the turn. Engineers said it can drop the speed by 10 mph in about one second when engaged.

Ford's system is engaged as soon as you start the car. Go around a corner too fast and the electronics jump in, cutting the throttle and applying the brakes, all in an effort to help you complete the turn. Even if a driver chooses to switch the vehicle’s traction control off, much of the system remains working in the background. If you get the car too out of sorts, the system will intervene to try to get the car back on track.

The magic of modern electronics makes the all-wheel-drive systems seamless to drivers, and that’s the point, according to Mike Murphy, Ford’s global small car marketing manager. In the Explorer, Ford has what it calls Terrain Management System. A rotary switch on the console allows the driver to choose from four modes: Normal, Sand, Mud/Rut and Snow. Each selection allows a slightly different amount of wheel spin before intervening. For instance, in deep sand or snow, you want the wheels to spin a bit to keep momentum, lest you get bogged down and stuck.

“All-wheel-drive gives our customers confidence and the ability to be secure when driving,” Murphy said.

In my test, the front-wheel-drive Fusion riding on all-season tires was capable getting around in the snowy conditions, although a much slower pace than the all-wheel-drive model. The all-wheel-drive Fusion was easier to drive with its predictable handling and ability to get the power down. If you live in areas where the roads get slick, the extra $1,700 to $2,000 the all-wheel-drive option costs, depending upon the vehicle, is worth it for the peace of mind. You may use it only a few times a year — but it's nice to know it's there when you need it.