Defensive Driving on Gravel
In many Countries rural areas are a large part of the road network and consists of low surface grade or gravel roads. The reason for this is that tarred roads are expensive to build, and are not particularly necessary if they don’t carry a lot of traffic. Gravel roads are inexpensive and easy to maintain. The only drawback is that people who use them have to drive slower and need to use a slightly different set of driving skills.
Most vehicles operators and handbooks explain how to drive on gravel roads. Unfortunately, many drivers don’t bother to listen or read the information available, and so every year a number of people cease being travelers and become statistics.
This content was developed by and owned by Paul Sinkinson, Xplorability owner. Paul is a 4wd Defensive Driver Training Consultant/Trainer and Programme Developer.
Excessive speed is the Major cause of accidents on gravel roads. It is highly advisable to keep to below a Maximum speed limit of 40 km/h. Lack of concentration is the second main cause, due to long driving distances and very little traffic.
Pay attention to road traffic signs. Particularly those that indicate a gentle or sharp turn ahead. You should reduce your speed accordingly.
Switch on your headlights in dusty conditions so that other road-users can see you.
Reduce speed when passing oncoming traffic and keep to the right side of the road as far as safely possible.
Tyre pressure plays an important role in the road-holding ability of your vehicle. Stick to the recommended pressures at all times. Check your tyres and tyre pressure every day.
Avoid driving at night. It is dangerous due to poor visibility and movement of the local wildlife
In rainy or wet conditions beware of slippery roads, wash-aways, and running water.
Always be on the lookout for wild animals and slow down immediately when you see them.
Keep both hands on the steering wheel at all times.
Always sit correctly in the driver’s seat when driving.
If you have a problem on a Rural Road, especially if you require vehicle recovery or repairs, you may need water as you wait for someone to come along. As a rule have a minimum two litres for each occupant and two litres for the radiator.
Here are some serious guidelines for driving on gravel. Use them and you could possibly save your life and the lives of other road users as well as minimizing vehicle damage.
I will not apologise for the fact that I may repeat certain points. I have done this in the hope that the information is taken in, absorbed and more importantly, retained. It may save your life and the lives of others.
Many vehicles today are permanent Four Wheel Drive with traction control and this does help with traction and stability on loose gravel surfaces. However, some still have the 2wd and 4wd facility. On loose surface gravel roads it is always advantageous to engage four wheel drive as this will provide better directional control. That said, do not be lulled into a false sense of security.
You may be in a hurry to get where you are going, but speeding is particularly dangerous on a gravel road (Rural and Forest Roads). The speed limit on a gravel road needs to be a leisurely 40 km / hour Maximum. Of course, there are exceptions such as the long distance unsealed roads in Australia where speed limits may be reconsidered and be higher BUT BE WARNED – Excessive Speed and lack of concentration on them will and does cause accidents.
ONLY When you have a clear view of the road ahead, Drive as close as possible to the center of the road. This will give you time to react. Slow down and move to the correct side of the road when a car approaches. Move to the correct when approaching Blind Crests. Roll your windows up to avoid being sandblasted.
Drive at a safe speed with mechanical sympathy
Occasionally someone will want to overtake you. When this happens, slow down and move safely to the correct side of the road. This will reduce the damage done to your car by stones that the overtaking vehicle throws up. Your visibility will be substantially limited by the dust of the overtaking vehicle, so, drive slowly until the dust trail subsides.
Keep an eye on the sides of the road for people and animals. Slow down if you see either. Animals are particularly dangerous. You don’t know if it they will jump out into the road in an attempt to get over before you arrive or if they will stay put.
If you slam on brakes, (vehicles without ABS) the car could skid and result in a rollover. Use your brakes gently. In a crisis try to pump the brakes gently and continuously. For vehicles with ABS the system should maintain directional stability
If it is dusty, hazy or raining, turn your headlights on so that other drivers can see you.
Keep an eye out for traffic signs, especially the signs for curves and sharp turns. When you see a turn or curve, you will have less road holding to work with if you encounter one of these, so slow down. The gravel tends to be pushed to the edges of the roads building up loose areas that can cause you loss of control.
Take extra care when you drive gravel roads in the very early morning or at night. Visibility is poor and animals will be on the move.
Slow down if it rains. The surface becomes slippery, roads get washed away in places and puddles may conceal holes that you would otherwise have avoided.
Check that your tyre pressures are at the recommended pressure. Check daily if possible. Tyre pressure plays an important role in the road-holding ability of your vehicle. Make sure at you have at least one spare wheel/tyre before setting off.
If you have a problem, you may need water as you wait for someone to come along. As a rule have a minimum of two litres for each occupant and two litres for the radiator.
When passing someone… make sure that the road ahead is clear of other oncoming vehicles and that there are no blind crests ahead and that you build up some distance before you turn in again. The stones that you throw up may break his windscreen. Slow down and drive to the middle of the road if you see pedestrians, cyclists, donkeys/horses or carts. The stones could damage them as well. Keep both hands on the wheel at all times.
Remember – Your safety and the safety of others depends on You!
This Driver was not concentrating – Perhaps he was talking with a passenger or on his mobile phone. He lost a wheel over the edge of the gravel road, turned to regain the road and braked at the same time. The weight transferred to the front – He lost control and the vehicle overturned.
Gravel roads are a fact of life for drivers in many Rural Areas. But, Urban Site, Gravel and any Sand or Desert roads present their own special road safety challenge. The issue is traction. Driving on loose gravel is harder than driving on Black Top because your tyres don’t have the traction needed to give you stable control. Throw speed into the mix, and you have a formula for trouble.
Construction materials, weather, traffic volumes, and vehicle weights can change a gravel road’s condition very quickly. That’s why it’s so important to approach gravel roads with caution each and every time you encounter one. It may not be the same road you traveled this morning. There are specific driving behaviours you can adopt that can help decrease your risk.
You can, with regular practice, find a suitable “Harmonic” speed to suit your vehicle for this type of surface. At that speed, the vehicle suspension movement becomes minimal which in turn allows a more comfortable ride. Be warned though that this speed may increase the likelihood of a loss of directional control on extremely loose surfaces especially on corners.
Have you ever wondered why you slide out so easily when cornering on Gravel roads?
Dirt and paved road curves differ significantly, and that has nothing to do with size and surface. This has to do with how they are constructed.
Paved roads are laid out with circle-drawing compasses. That doesn’t mean they are circles, but it does mean that they are regular curves. When you enter a paved curve and give the steering wheel a “set,” the road more or less holds constant. Paved curves almost always go from straight, transition to a fixed, regular curve, then straighten out again with no irregularities in between. This makes for easier and safer driving.
Dirt roads usually follow the Natural Contours of the land. This leads to irregular curves. Irregular curves mean the radius varies: They may get tighter and tighter, or straighten out faster than expected. That may be the reason we unexpectedly have a vehicle slide because it isn’t exactly what we were expecting.
IMPORTANT! Not all gravel roads are the same. Please be aware of the road conditions and adjust your driving style accordingly
Why does this happen? Similar to the asphalt top course on paved roads, gravel is the “wearing surface” of an unpaved road. The large stones, in contact with each other, distribute vehicle loads to the road base beneath it. The stones are held by smaller particles, especially “fines.” With insufficient fines, vehicle tyres more easily move the stones. As their particle-to-particle contact decreases, so also does their ability to distribute loads.
In addition, continuing traffic begins to move the stones into the pattern of ridges and valleys. Traffic causes corrugations in two ways:
The degree of damage depends on tyre hardness and vehicle acceleration, deceleration, turning, and speed. Because hard tyres excert greater force per square inch on the road surface, they break and scatter aggregate more than do soft tyres. Acceleration, deceleration, and turning also increase tyre-to-road surface forces. Therefore, corrugations usually occur first at road and driveway intersections, and at tops and bottoms of hills.
High speeds increase both tyre force and bouncing. Fast moving vehicles, therefore, quicken the formation of corrugations and increase their depth.
These factors have the greatest effect on roads with a weak base, poor drainage, or both. A weak base deflects under loads, and becomes deformed into the same wave-like pattern as the surface. Poor drainage leaves water in the road, or allows it to percolate in from the sides. Too much water lubricates the base and surface particles. Thus, water increases particle movement, and corrugation formation and depth. These Corrugations can be found anywhere on the road but more often in areas where vehicles slow down or accelerate. IE: Junctions, turns and curves, hill crests and the base of hills on the route.
Remember, Reduce your Speed … .
Drive with mechanical sympathy!
This content was prepared for the Off-Road Discovery Website by Xplorability 4wd Training
The Content - All Photographs and Photographic Copyright and All other Rights other Reserved October 2017. S.W. France This content may not be copied or reproduced without the written consent of Paul Sinkinson – Xplorability Training.
For Use Only in 4wd and Light Vehicle Driver Training.
Not for Re-Publication, Distribution or use outside the Xplorability Training Programme