CAUSES OF SKIDDING AND LOSS OF TRACTION
The causes of skidding (loss of traction) can be divided into three groups: (1) conditions of the road, (2) conditions of the vehicle, and (3) actions of the driver.
Section 1 – Conditions of the Road
Ice, snow, or frost.
Wet road, particularly when the road surface has drops of oil and particles of rubber – especially with the first rain after a long dry spell.
Mud on the road, which can be found near farm entrances, outside building sites, and truck crossings.
Packed wet leaves, which occur in the fall.
Broken or uneven road surfaces and sand/gravel commonly found on curves.
Adverse camber on curves (when the road is banked the wrong way on a curve) or when the curve is flat – loss of traction can occur even if the road surface is dry, but especially when the surface is slippery.
Section 2 – Conditions of the Vehicle (mainly brakes and tires)
Brakes should be evenly adjusted so that on application of the brakes the vehicle slows down in a straight line. If the brakes pull one way or the other, a skid can easily occur. Front wheels being out of alignment also can cause a skid by pulling the vehicle one way or another when the brake are applied.
Tires should have good tread, and preferably the front and rear pairs should be well matched, and the tire pressure should be correct. If there is a different pressure in one tire from that in the opposite one, the effect can be similar to that of unevenly adjusted brakes because one tire will drag more than the other tires.
Section 3 – Actions of the Driver (misuse of the four main controls)
Steering wheel – sudden steering action on a slippery surface.
Accelerator – abrupt or sudden changes in the vehicle’s speed.
Brakes – panic stops and applying your brakes too hard – especially on hills, curves, or wet surfaces.
Clutch – sudden engagement of the clutch when on a slippery surface.
Combinations – skids are most often caused by excessive speed, coupled with too sharp a turn for the vehicle or braking when turning, or "normal" speed coupled with ice or snow or gravel on the road, etc.
Section 4 – Hydroplaning
Hydroplaning takes place while driving on wet roads. At speeds up to 35 MPH, most tires will "wipe" the roadway surface (in much the same manner a windshield wiper clears the windshield) of up to about ¼ inch of water. However, as the speed increases, the tire cannot "wipe" the road as well, and they start to ride up on the water, just like a set of water skis. In a standard passenger vehicle, partial hydroplaning starts at about 35 MPH and increases with speed up to about 55 MPH, at which point the tires can be totally up on the water. In a severe rainstorm, for example, with less than 1/8 inch of tire tread, the tires may not touch the road at 55 MPH. If this is the case, there is no friction available to brake, accelerate, or corner. A gust of wind, a change of road camber, or a slight turn can create an unpredictable and uncontrollable skid.
With today’s lesser crowned roadways, especially freeways, hydroplaning is an increasingly important factor in automobile accidents. A driver can normally predict areas where hydroplaning will occur, but not always; you may suddenly find yourself in a hydroplaning situation. If you do, the best thing to do is to take your foot off the accelerator and allow the vehicle to slow down without braking. If you skid while your vehicle is only partially hydroplaning, you should be able to regain control by correcting (steering and counter steering) for the particular type of skid that occurs. On the other hand, if you’re totally hydroplaning, about all you can do is release the accelerator and ride out the skid without braking.
To prevent hydroplaning, it is most helpful to have properly inflated good tires with deep tread, at least 1/8 inch. The tread allows the water to escape from under the tires and tends to prevent complete hydroplaning at normal highway speeds. However, when the depth of the water exceeds the depth of the tire tread, complete hydroplaning can be expected at speeds from 50-55 MPH.