Many drivers assume that
four-wheel drive vehicles are either hulking off-road monsters or high-priced racing vehicles. While it is certainly true that such high-performance cars and trucks require four-wheel drive, the improved traction control and handling provided by four-wheel drive is slowly creeping into regular commuter vehicles, where it has been shown to offer advantages in safety, speed and handling. Subaru has offered four-wheel drive wagons and sedans for well over a decade, as have Saab and Volvo. In recent years, Ford, Mitsubishi, Citronen, Volkswagen and Honda have all begun offering four-wheel drive options on various hatchbacks and other small cars, taking what they learned from the rally circuit and applying it to the "hot hatch" market. While four-wheel drive comes at the cost of tire wear and fuel consumption, modern technologies to minimize these downsides and maximize the speed, cornering and handling benefits, causing many engineers to claim four-wheel drive will one day become as standard as anti-lock brakes and seatbelts.
The primary advantage of
4WD systems is that they ensure the maximum amount of contact and control on the road. Two-wheel drive cars, especially small or light vehicles, are notorious for losing grip on one or more of the tires, especially in heavy wind, rain or snow. In a 2WD car this can be disastrous if one of the tires losing grip happens to be connected to the engine, since this will cause the car to violently buck in the direction of the gripping tire and oversteer into a spin. Additionally, 2WD cars, especially rear-wheel drive vehicles, have difficulty getting out of deep mud, dirt and snow because not all the wheels are receiving power from the engine. This means that when one of them slips, the car is unable to grip, and becomes stuck. The lack of grip also makes it difficult for 2WD vehicles to climb inclines, especially on unimproved road surfaces. New four wheel drive vehicles have none of these problems.
This is why almost all working trucks, especially farm and hunting trucks like the Toyota Hilux, have four-wheel drive. In the event that any of the wheels loses grip due to lose ground, slippage or mud, the remaining wheels are still able to deliver power and propel the vehicle forward. Momentum is the best way to fight a loss of grip, and so keeping the vehicle moving through, over and around any slippages is the best way to keep it moving. The same also applies for high-performance racing vehicles, whose advanced traction control requires a 4WD system in order to pull power away from whichever wheel is gripping too firmly on a turn and apply it to whichever wheel needs more.
Experience with four-wheel drive cars off-road and on rally circuits led car designers to understand that four wheel drive is about more than just having fun in the dirt; it provides on-road safety. Mitsubishi has been a forerunner in this, thanks to their recent spate of success in the rally circuit. By ensuring that the car always has steady grip, designers can ensure that the driver is always in control. This allows them to avoid other cars as well as turn more effectively, proactively preventing accidents.
