Snow chains are not necessary for cars that come equipped with traction aids such as four-wheel drive. Four-wheel drive vehicles are able to navigate snowy weather.
Many local and state governments require their citizens to drive with snow chains in snowy weather. Four-wheel drive vehicles and all-wheel drive vehicles are usually exempted from such requirements because their drivetrains feature multiple differentials to provide the necessary power for accelerating in inclement weather conditions. While the drivetrain of a two-wheel drive car features only one rear differential, the drivetrain of a four-wheel drive car features two, and that of an all-wheel drive car features three.