All methods of driving a single car are applicable for a road train, however, due to its significant weight and dimensions, there are also features. A road train is a tractor vehicle with one semi-trailer or with one or more trailers.
The braking distance of a road train is greater than the braking distance of a single tractor. During the movement, the trailer constantly deviates to the sides from the trajectory of the vehicle-tractor, which increases the danger during overtaking and oncoming traffic. Therefore, driving a road train is much more difficult than a single car. The maneuverability of a road train is worse than that of a single car.
The driver should take into account that during the turn of the road train, the trailer shifts towards the center of rotation and the corridor of the road train will increase. This circumstance is especially significant when the road train moves along the city streets and turns at intersections have a small radius. There is a danger of the trailer entering the sidewalk, where it can injure pedestrians, knock down the mast of the light or traffic light, damage the green spaces.
Some trailers and semi-trailers have steered wheels that turn in a bend and allow the wheels of the trailer to move along the track of the tractor. Driving road trains with such trailers is somewhat easier. Reversing the road train is particularly difficult. At the same time, a pushing force acts on the trailer, and it tends to go sideways. The driver has to constantly change the position of the steered wheels of the tractor, while small errors give large trailers to the side. Extensive experience is required in order to reverse the trailer to a precisely designated place on the first attempt.
You can start the movement of the road train only in first gear, carefully including the clutch.
You can stop the train only on straight sections, so that all of it is located on one line. When braking on a curve, skidding of the trailer or folding of the road train may occur, which may be followed by tipping over, pushing the towing vehicle into a ditch or breaking the towing device.
- Before a long climb, you need to turn on the gear in advance, in which you can overcome the whole climb, so as not to shift gears on the rise, while losing speed.
- On long descents it is necessary to hold the road train from acceleration to high speed.
For this purpose, you can apply engine braking or enable the auxiliary brake system (if any). If this is not enough, apply: service braking. During movement, you should periodically pay attention to the movement of the trailer (through the rear view mirror), to the reliability of securing the load. In case of any spontaneous change in the driving regime, find out its cause and take measures. Perhaps the trailer pulled over to the side of the road, perhaps one of the trailer wheels has lowered, there are known cases of the trailer breaking away from the tractor.
The brain was given to man not only so that he was, but also to think. It is desirable often, and not sometimes. Impartial statistics show that the lion's share of all accidents (85%) is the fault of drivers and pedestrians. Another 5% of accidents due to the technical condition of vehicles (we have this figure more), and 10% - a consequence of unforeseen situations (for example, the appearance of an animal on the road). The figure of 85% can be painted as follows:
46% - erroneous assessment by the driver of the traffic situation,
25% - sleep while driving,
15% - in an alcoholic or narcotic state (according to German statistics),
14% is different.
Preventing an accident is much easier than eliminating its consequences. To do this, it is important to know the theory. Practice in the form of extreme driving courses will help, but not often. For a person, especially a Russian, it is typical to confuse a causal relationship. Therefore, our drivers first learn to take turns with a skid or skip a red light intersection on a road train (bus, minibus, passenger car, motorcycle), and then scratch their turnips and think about what happened when looking at scrap metal, and even worse, corpses.
- Rule number of times: a car is a source of increased, and often fatal, danger. You should always remember that you control a very massive projectile, which also resists turning at speed, but most importantly, it does not stop quickly.
- Rule number two: look ahead not only a meter from the hood, but also how much vision is enough to see and, therefore, predict the situation “several steps” ahead. In addition, turn your head and rotate your eyes 360 degrees. The driver, as a chess player, must calculate the situation. I dare to assure that with the driving experience you will not only calculate, but also feel the situation as an interesting place. For some people, the ability to analyze comes with the genes of their parents, while others earn in life. I have a friend who, with almost no driving experience, calculates the traffic situation so that only you wonder. But I don’t like to ride with him, because he, as an advanced navigator, mutters over his ear all the time, telling what will be ahead in the foreseeable, literal sense, future. True, he graduated from the Mechanics and Mathematics Department of Moscow State University.
It is important to be able to not only turn the steering wheel back and forth, but also correctly calculate the stopping distance. On dry asphalt, this is obtained by almost everyone. But on wet or slippery, especially in autumn or winter after the dry summer season, not everyone has it. If you slipped and fell, then the fifth point will level the consequences. If the 40-ton “truck” “slips”, then the elephant in the china shop will turn out to be a child’s babble of what the road train will do. And now the theory.
If in Europe the preference on main road trains is given to disc brakes “in a circle”, then due to the specifics of the technical condition of the park, we have drum brakes. “Drums” are significantly inferior to disc brakes not only in terms of information content of the degree of deceleration, but also in efficiency. A road train with a speed of 80 km / h has a braking distance: - with drum brakes on all wheels - 60 m, - only front disc brakes - 45 m, - disc brakes on all wheels - 42 m.
The “discs” on the front axle immediately reduce the braking distance by 25% compared to the “drums”, although the further installation of disc brakes on all axles already reduces the braking distance by only 6.5%. This means that the maximum braking effect is transmitted through the front axle. Practice shows that the load on the front axle during braking can reach 13 tons (for a road train). Now it is clear that not only the condition of the tires, but also the entire suspension and support elements of the front axle play a huge role in braking. How many trucks with defective shock absorbers, thrust bearings and broken pivots drive on our roads! It is naive to think that tires have a better condition. From the foregoing, it is clear that rubber (its size and condition) can significantly reduce the stopping distance.
A Russian invention is to turn off the brakes on the front axle for the winter. It is practiced on “maz” and “kamaz” and is motivated by the fact that when braking on slippery roads, the front wheels quickly lock and the car loses control. In addition, the rear wheels fall onto a film of water that forms after the front wheels. The braking effect of the rear axle in such cases is zero. All this takes place and there is nothing to advise here, except to not drive them at such a time of the year or buy new trucks with anti-lock systems.
The main merit of the ABS is the preservation of directional stability during emergency braking. Today, all trucks in Europe go off the assembly line with ABS, and their operation with a deliberately faulty system is a prison. I found those times when I rode a road train in Europe with a trailer without ABS, but with a tractor equipped with it. The Poles turned a blind eye to this until they entered the EEC, and the Germans never caught. Moreover, if the tractor were without ABS, and the trailer with it, then even the Poles would not be allowed, since in such a combination it’s easy to fold the coupling.
Another myth - braking only with the help of a "parachute" is effective and is a panacea for folding the road train. I remind you that a “parachute” is a brake valve that is displayed in the driver’s cab, with the help of which the braking torque is transmitted only to the trailer wheels. About 10 years ago it was widely distributed on all imported cars. Now, with the introduction of new generation brake systems, it is practically not installed on European trucks. Since there are a lot of old foreign cars in Russia, it is found quite often. So, many "experienced" advise them to slow down on a slippery road, especially on the slopes. I tried and slowed down - the coupling unfolds for a sweet soul.
Smart books say that the braking of a road train can occur in three ways:
- tractor and trailer braking synchronously. This is ideal, but practically unattainable.
- trailer enhances tractor braking. In this case, the train is stretched, which excludes its folding. This is possible only with an increase in the response time of the braking system of the tractor, which significantly reduces the braking efficiency of the road train as a whole, since the maximum braking effect should be on the front axle of the tractor. In addition, the likelihood of achieving full slip of the trailer wheels increases. According to the laws of physics, the trailer in such cases necessarily begins to slide downhill, most often on the sidelines. What happens when braking is only a "parachute."
- when braking, the trailer rolls onto the tractor. Sometimes this leads to the folding of the road train. But of the two evils, the designers chose the least - the third option is braking. From the foregoing, it is clear that braking only with a trailer on a slippery road is deadly.
Therefore, the "parachute" is intended only for unloading the brake system of the tractor on long descents with dry asphalt in order to avoid failure of the working system when the latter overheats. But experienced drivers masterfully straighten their hitch with the threat of folding.
With the introduction of effective modern auxiliary brake systems (engine brake, hydraulic retarders and fastards), the need for a “parachute” has disappeared. But, as my experience shows, many drivers are completely unable to use such systems. Transport journalists also contribute to this. Some “experts”, having tested a modern engine brake at engine speeds of 1000–1200 rpm, write about its low efficiency. Citizens-drivers, the engine brake is most effective at engine speeds of 1800-2100 rpm, that is, at maximum. Therefore, in order to effectively brake them, you must constantly switch to lower gears. Only then will you not have a gram of doubt about its effectiveness. Do not forget that modern engine brakes of different designs have several stages of braking. Do not try to brake at the very first - it is only for braking.
As for the braking system of the road train, I had to listen more than once from the "experienced" that the parking brake system of the tractor also brakes the trailer. Therefore, many drivers, having unhooked, do not put shoes under the wheels of the trailer even on a slope, naively believing that there are energy accumulators on its axles. In fact, trailers are equipped with brake chambers, and only its paws serve as anchors. Therefore, do not be too lazy to put shoes under the front and rear wheels of the trailer in order to avoid problems during disengagement.
Another observation of a long practice - drivers do not know how to emergency brake.
In critical situations, the vast majority of the car stalls. Almost all drivers press the brake with all their might, forgetting to squeeze the clutch - this threatens to stop the engine. You always need to control the situation, and with improper emergency braking, a stalled engine blocks the drive wheels and the car loses control in any case - you cannot maneuver. Proper emergency braking - a strong simultaneous hit with both feet on the brake and clutch pedals. Only then can you control the movement of the machine. By the way, on trucks with an automatic gearshift system during emergency braking, the electronics themselves disengage the clutch (on Scania vehicles with opticruise, it is necessary to squeeze the clutch).
Many articles raised the issue of the inconsistency of the ABS capability with the Rules of the Road in Russia. I also asked German instructors about this. Oddly enough, with all the German thoroughness and punctuality, the mess with this issue in Germany is even greater. The main principle of emergency situations is that the truck driver is always to blame, since he deliberately controls a source of very high danger. The presumption of innocence does not work here at all, even if the drunkard rushed or drove under your truck. In such cases, only a lawyer will help, whose services, by the way, are already automatically included in the insurance. Looks like they have good lawyers, otherwise there would be no driver-professional profession in Germany.
The main factors affecting the stopping distance: speed, load, reaction time. When the speed is doubled, the braking distance increases by four. German instructors with a pencil in their hand showed quite convincingly how speed affects the stopping distance of a truck. Imagine that a 40-ton road train at a speed of 50 km / h begins to brake urgently. Let us remember the place when the driver took action to brake. In front of the bumper of a stopped truck, we put a car for clarity. We repeat the same action, but at a train speed of 70 km / h. The driver starts to brake urgently from the same place as the first time. The difference in speed is small, only 20 km. What do you think, at what speed does the road train hit the car? Most of our group decided that the speed would be about 20 km / h. When the Germans announced the figure, at the time of the collision 58 km / h, I was very surprised. It consists of the reaction time of the driver (about 1 second), the distance that the road train passed during the reaction of the driver and the braking distance. This example clearly shows how important the speed of the machine is and what consequences occur even if, in our understanding, its excess is small. It becomes logical to limit the speed in cities where the collisions are very large, at 60, or even 50 km / h.
Not convincing? Another example:
The braking distance of a passenger car at a speed of 100 km / h is the same as that of a 40-ton road train at 80 km / h. The difference in speed is only 25%, the difference in weight is 2700%. It would seem that a car should slow down much more efficiently, but this minimal difference in speed negates the monstrous difference in weight. It should also be remembered that the slope of the track significantly increases the braking distance. For example, on a 9% slope it increases 2.5 times.
Driving a tractor with a semi-trailer. How to drive a truck tractor
Today, many driving schools provide auto-instructors who teach the correct management of long-length and large vehicles. It is important to understand that driving a truck or a long vehicle is significantly different from driving a car because of the special parameters of the car. All this must be taken into account, especially if training is required for further transportation of goods and goods by trucks.
Training and improving skills is very important for further work in the field of cargo transportation, because the driver must be ready for new tasks, problems and situations on the road. In the lessons of driving large-sized vehicles, increased attention is paid to the following issues:
- the trajectory of the van,
- wheel displacement and movement.