will increase steering forces required to turn the vehicle. Furthermore, automatically locking differentials can cause a loss of control on ice where an open differential would allow one wheel to spin and the other to hold, while not transferring power. An example of this would be a vehicle parked sideways on a slippery grade. When both wheels spin, the vehicle will break traction and slide down the grade. Alternatives Limited-slip differentials (LSD) are considered a compromise between a standard differential and a locking differential because they operate more smoothly, and they do direct some extra torque to the wheel with the most traction compared to a standard differential, but are not capable of 100% lockup. Traction control systems are also used in many modern vehicles, either in addition to, or as a replacement of, locking differentials. Examples include: Volkswagen's electronic differential lock (EDL), Opel's TC+ installed for the first time in Opel Astra G (2001), et cetera. This is not in fact a differential lock, but operates at each wheel. Sensors monitor wheel speeds, and if one is rotating more than a specified number of revolutions per minute (e.g. 100) than the other (i.e. slipping) the traction control system momentarily brakes it. This transfers more power to the other wheel, but still employs the open differential, which is the same as on cars without the EDL option. If all drive wheels lose traction, then throttle control may be automatically applied. Electronic traction control systems may be integrated with anti-lock braking systems, which have a similar action on braking and use some similar components. Such systems are used for example on the most recent Nissan Pathfinder, Land Rover Defender, Land Rover Freelander, the McLaren P1 and the McLaren 650s. Applications Some utility vehicles such as tow trucks, forklifts, tractors, and heavy equipment use locking differentials to maintain traction, especially when driving on soft, muddy, or uneven surfaces. Lockers are common in agricultural equipment and military trucks. On some farm tractors, there is a pedal that can be stepped on with the operator's heel to lock the differential as needed. Differential locking can also be used in the sport of drifting as an alternative to a limited-slip differential. Four-wheel drive vehicles that drive off-road often use a locking differential to keep from getting stuck when driving on loose, muddy, or rocky terrain. Locking differentials are considered essential equipment for serious off-road driving.