When the rear end of a vehicle or aircraft slides back and forth, this is known as fishtailing. Typically, fishtailing is the result of a loss of driver control, although it is sometimes deliberately instigated by stunt drivers to achieve a desired effect. For regular drivers, fishtailing can be very dangerous, although it isn't always a sign of bad driving. Hidden conditions like black ice can cause a responsible driver to fishtail even when he or she drives perfectly. Generally, fishtailing is more common rear wheel drive vehicles, although front wheel drive cars are not exempt from this problem.
Several things cause fishtailing. Conditions like ice, water, and snow can cause a car to fishtail because they reduce traction on the roadway, which can cause the rear wheels of a vehicle to slide out of control. The risk of fishtailing also increases at high speeds, or when a driver brakes very suddenly. In some cases, a car may start to fishtail when a driver approaches a curve poorly. Drivers who deliberately fishtail usually try to turn the fishtail into a slide, as is the case with people who engage in drifting.
For drivers who did not intend to fishtail, it can be a scary experience. The whole car tends to shake and wobble, and it will drift out of control across the roadway since the rear wheels have lost their traction. In some cases, a bout of fishtailing can cause a car to turn completely around, or it can launch a car into a lane of oncoming traffic. It is also sometimes possible to hear the gas in the tank sloshing around, which is why some people call fishtailing “tank slapping.”
To recover from a fishtail, drivers should stop accelerating and steer in the direction of the skid as best they can. The wheel shouldn't be yanked or jerked, as this can cause the fishtail to get worse. For drivers who start fishtailing in traffic, it is a good idea to try and direct the skid to the side of the road so that they are not thrust into the path of oncoming cars. Drivers should also avoid sharp braking, which can make the skid worse.
Ideally, of course, drivers should avoid fishtailing altogether unless they have received training in stunt driving and they are on closed driving courses. If you know that you are going to be driving on low friction roads, drive slowly, avoid sudden braking, and take turns slowly, accelerating out of the turn to increase your traction. If you live in a region which is prone to black ice, try to avoid driving in the early morning and evening, when black ice is at its worst.