While the two major hazards in winter driving are commonly referred to as poor traction and reduced visibility, research has shown that there are six important problems which confront the commercial drivers.
- Poor traction - Being unable to pull away from a standstill on an icy road, to go up slippery hills or to negotiate deep snow can cause trouble ranging from aggravating delays because of burnt tires to major traffic tie-ups and collisions.
To improve traction, good tire treads are necessary. Start off slow and easy, and do not spin your wheels, because this only digs you in deeper. In deep snow, in order to get room to move, a good idea is to turn your wheels from side to side to push the snow away from the tires. Another good trick is to move your vehicle back and forth four or five feet before you shut down. This packs heavy snow. When you are pulling out use a light foot on the accelerator, easing forward gently.
- Reduced ability to stop - On ice and snow it takes three to 12 times more stopping distance than required on dry roads. These longer stopping distances contribute to the cause of many winter collisions.
Test studies indicate that the heavier the vehicle the greater the stopping distance. Under severe winter conditions this gap widens accordingly. Gearing down of the vehicle also assists in bringing it to a safe stop.
- The effect of temperature on starting and stopping - Temperature plays an important part in braking distance and traction on ice and snow. As the temperature rises, ice becomes much more slippery.
Your braking distance can double with a temperature variation from -18ºC to around 0ºC. It is important, when driving in winter weather, to periodically get the feel of the road. This should be done only at a slow speed.
The chart shown below shows the effect of temperature on braking distance, with a tractor and semi trailer on ice, gross load 19,100 kg.
- Ice and snow made slippery by traffic - The action of tires spinning and sliding on snow and ice greatly decreases traction on already hazardous road surfaces. This happens mainly at intersections, on curves and on hills. This polishing of the road surface increases braking distances, slows traffic and presents a severe hazard at intersections. It's up to you to understand this fact and compensate for it in your driving. Slow down before you reach that slippery intersection and slow down before getting into a curve or before going down a hill. Adjust to the existing road, weather and traffic conditions. Gearing down may be necessary to slow down safely.
- Reduced ability to see and be seen - Winter driving hazards can be avoided, but you've got to see them.
Driving without completely clearing your windows invites disaster. Before starting your trip, clean off the entire windshield and all windows. Wipe off the headlights, brake and tail lights and turn signals so that others may see you. This may be necessary several times during a heavy storm. An extra few minutes could save your life.
There is a tendency by many drivers to overdrive their headlights. A heavily loaded truck travelling at 100 km/h requires approximately 138 m of braking distance. Therefore, with headlights strong enough to illuminate 108 m ahead, a vehicle could travel 31 m beyond where an object was first seen. The effective range of headlights varies greatly and the visibility of objects is affected by many factors. When driving at night or during adverse weather conditions, use headlights - not parking lights - to increase your ability to see and be seen.
Road spatter can leave you driving blind. Use your windshield wipers often. At night, stop occasionally to clean off headlights. In fog or heavy snowfall keep headlights on low beam and adjust your speed accordingly.
Run your heater and defroster a few minutes before you start out. You'll prevent sudden fogging of your windshield.
Wipers should be in top condition - both blades and arms. If new blades are installed they can be inefficient if arm pressure is inadequate. This shows up in poor wiping. Pressure of one ounce per inch of blade is needed and recommended.
- Jackknifing - There are two distinct kinds of jackknifing:
- A tractor jackknife in which the tractor rear skids sideways.
- A trailer jackknife in which the rear of the trailer comes around.
Repeated tests have shown that if a jackknife develops beyond 15 degrees it is almost impossible to recover. The faster this 15 degree angle develops the greater the severity and potential damage of the jackknife.
Since a jackknife can go to 15 degrees in length in one and half seconds, any attempt to recover must be fast in order to take preventive action.