In addition to the conclusion in the name, in fact, the movement implies a stop. You slow down at a traffic light pedestrian crossing, in front of another car and the like many times per trip. Sometimes (usually more often than you would like) you have to stop very quickly and abruptly. There are 2 terms to be distinguished in this regard: stopping distance and stopping way. They mean different things, although they are connected by a common purpose: to show the driver that the laws of inertia apply to any car.
What is the difference
The braking distance for each car is a static indicator. It is measured by engineers on tests, indicated in extended specifications. Of course, we are still talking about ideal conditions. These figures will not be taken into account. wet asphalt, worn pads and . Therefore, you should not take these numbers as something magical that will make your car slow down equally on dry new asphalt and on wet ice. You just need to focus on them, nothing more.
Much more significant indicator for the driver (and much more subjective, no matter how paradoxical it may sound) there will be a stopping path. What is meant by stopping distance can only be measured once. Most likely, each time the numbers will be different, this is determined by the very essence of the indicator. So, this is the distance that the car travels from the moment the driver notices the obstacle to the moment it comes to a complete stop. That is, this indicator depends on the speed of your reaction, on your concentration on road conditions, on the force with which you press on the brake pedal ... Naturally, all this is very individual. You can say that the numbers should not differ too much, and we would agree with you if it were not for one “but”: the time between “notice” and “realize” depends very much on your condition. An outside observer can at least somehow appreciate it, but you yourself are not capable of it. In particular, this is why it is forbidden to drive drunk. Your reaction slows down, but you yourself do not realize it; therefore, a drunk driver poses a huge danger to all road users, including himself.
How to count
Formulas for calculating the stopping distance, respectively, do not exist. Our mathematical apparatus is not capable of processing such a number of variables. So please don't take your eyes off the road while driving.
Stopping distance is often identified with the length brake track. Although these indicators do not mean the same thing, they follow one from the other. Therefore, we will not deviate from the generally accepted practice. In this sense, the braking distance is widely used in the analysis of traffic situations; for example, knowing the mass of the car and measuring the stopping distance, you can determine the speed at which the car was moving. If we talk about the finished formula, then this is how it looks:
V a - in fact, the speed that we need to calculate;
t c - time of braking amplification;
j - set braking time (taken from the table);
S u - the length of the brake track.
Note that the units of measurement in this equation are seconds and meters. Accordingly, you will receive the answer in meters per second; we warn not to confuse you. At first glance, the formula is not so complicated. However, the calculations can confuse you due to the rather large number of parameters and their opacity. For example, the braking boost time somehow doesn't intuitively appear in your head when you look at the trail. Determining the speed along the stopping distance still remains the lot of experts. Now imagine that in addition to this, you need to take into account a dozen more parameters related to you and your condition. Represented? This is difficult for a person unprepared for mathematics, physics and ballistics, so we will also leave the calculations to the experts. They need to do something.
And then what
It is possible to calculate stopping distance car, but we think it's pointless. It is somehow hard to imagine that a driver, especially an inexperienced one, at the moment when you need to make a decision, begins to substitute numbers in the formula. There are averages, and you should focus on them. Let them be approximate, but they can tell you the order of the numbers, the "fork" of values. There are tables of stopping distances of a car depending on its class, because, of course, a heavy SUV slows down in a completely different way than a minicar. These tables are compiled for a speed of 60 km/h. But be careful, the proportion for the calculation is insidious, it multiplies the values by the square of the "delta", that is, if the speed is increased by 2 times, the braking distance will increase by 4 times!
There are certain standards for the weight of a car of a certain class. It is unlikely that, say, a huge pickup truck will weigh less than one and a half tons (we would put, in fact, 2 tons). But a sports car or supercar, the body of which is made almost entirely of carbon fiber or some other hyper-innovative material, is a completely different matter. It does not fit into any table, and it does not belong there. That is why the values in the table are averaged and they are given for owners of production cars.
These values, as we have already written, should not be taken by you as the ultimate truth. These are ideal figures, only professional racers on completely new cars can repeat them. This table can show the stopping distance for wet road, but we all know that "wet" is not the same. Downpour or rain? Plus on the street, zero or minus? Day or night? So the table is not a panacea. Yes, it's useful for letting you know how far your car will roughly travel after you've pressed , but no more. Anyway, you need to be careful and keep your distance on the road.
No calculator needed
To somehow calculate the stopping distance of your car, you need knowledge, perseverance and a lot of data. So this, as we said above, is not very useful. Instead, it is better to take steps to reduce this value, even if you do not know it to the nearest centimeter. Regularly check the condition of the brake system, top up brake fluid change pads. And carefully look behind the road, it can save not only yours, but also someone else's life.
However, don't overdo it. Of course, but if you figured out that your stopping distance will be approximately, say, 20 meters, this does not mean that you need to keep exactly this distance between your cars. Be a sane person. The car in front is moving at a speed comparable to yours, and it also has mass, so it won't be able to brake instantly. Therefore, a few meters between you will be enough.
Another important point for you: is your ABS machine? If yes, then this system will protect you from locked wheels during any braking, especially during hard braking. So, you will not be carried into an uncontrolled skid. If this system is not on your car, then do not press the pedal with all your might. Raise your leg periodically, just a little. This will loosen the pressure of the brake pads, allow the wheel to spend at least a small part of the braking inertia on scrolling, and again, will not let it go off track.
In general, our recommendations are banal to the point of impossibility: monitor the state of your car's systems, watch the road, do not drive drunk or sleepy, and remember that the road is dangerous. Don't relax and it will save your life.
Carelessness looks impressive only in well-thought-out scenes from action films and detectives. In fact, most drivers don't even realize what kind of danger they are talking about when talking about keeping their distance and speeding. How many fell from a height of three meters flat on the concrete floor? Hardly. But in fact, a person in a car will experience exactly the same load when hitting a fixed obstacle at a speed of ... only 28 km / h.
Why know the stopping distance
Since we started with the calculations, talking about the stopping distance of a moving car, we use a simple physical formula known to every student. It is used to calculate the transition of falling energy into kinetic energy at the end of the path (mgh=mVx2/2). From here we get that at a speed of about 30 km / h the body receives a blow equal to a fall from a height of three meters. Accordingly, when moving at a speed of 60 km / h, the impact force will be equal to a fall from a height of 15 m, and already at a speed of 90 km / h - from a height of about 32 m, 120 km / h - this is already a height of 55 meters.
Even considering that the airbag deploys in the car, survive with frontal impact At a speed of 60 km / h, there is very little chance. This is the approximate height of the Khrushchev. Will someone dare to jump from the roof of a five-story building, tied inflatable pillows? Hardly. And what about the speed of 90 km / h, the impact at which is tantamount to falling from the height of a ten-story building? And from a height of 55 meters? There is no chance of survival, and this is even on the condition that the airbag works flawlessly.
Empirical formula for calculating the stopping distance
Having an excellent driver's eye and sufficient experience, everyone will be able to determine the distance to an object by eye, at least approximately. Driving experience shows that in order to instantly calculate the braking distance from speed, you just need to glance at the speedometer, estimate the distance to the obstacle, then the braking distance will be equal to half the number that the speedometer shows. That is, based on the empirical formula for calculating the stopping distance, safe distance to any object will be equal to the instantaneous speed divided in half. In almost the same way, the calculation of the speed of the car along the braking distance is performed.
At the same time, it is necessary to take into account such a concept as a stopping distance, this is the term of experts traffic police and it takes into account not only the stopping distance itself, but also the reaction speed, as well as the response time of the brake system. In principle, this is the distance to the absolute stop of the car from the moment when the driver has fixed the obstacle. Naturally, the stopping distance is always greater than the braking distance, since average speed reactions of healthy and sober driver about 0.8 s, and brake system works for another 0.2-0.3 s. Therefore, it will take another 1.1 seconds before the car comes to a complete stop, and at a speed of 60 km/h, the car travels 16.6 meters in one second. Almost seventeen meters, which will inevitably add to the braking distance and which is rarely taken into account by most drivers. That is precisely why it is necessary to take seriously at least the theoretical calculation of the braking distance.
What you need to calculate the braking distance
To calculate the stopping distance, the formula of which is shown in the figure with explanations, it is not enough to know instantaneous dry data.
Theoretically, to evaluate braking performance machines need to use a lot of data:
- stopping distance;
- the minimum time for which the brake system will work;
- range of brake force change;
- algorithm for changing braking forces;
- brake performance depending on heating;
- quality pavement;
- vehicle suspension efficiency;
- the degree of wear and type of tires.
Here it is necessary to take into account whole line moments. For example, the efficiency of the brake system in each car can be different and this goes without saying. Hydraulic system brakes give a delay of at least 0.2-03 s, and pneumatics installed on most trucks and buses even more, up to 0.6 s. In addition, there is such a thing as an increase in braking force from zero to a maximum value, and this also takes from 0.4 to 0.6 s, while the effect of the speed of movement on the length of the braking distance in this case increases squared, that is, with an increase speed twice, the stopping distance will be four times longer.
Additional components of the braking distance
When calculating the effectiveness of the brakes, the characteristics of the suspension and the condition of the tires are very important. What's with the suspension? Very simple. Ideally smooth asphalt is quite rare under our wheels, namely the suspension, more precisely, shock absorbers, springs, torsion bars and springs just press the wheels to the surface, making braking and steering as efficient as possible. If the shock absorber is defective, the wheels bounce over bumps and full contact with the surface is out of the question.
Let's add to this the coefficient of adhesion of rubber to the road - the condition of the road, the type of tire (winter or summer), the tread pattern, geometry, tread wear and the quality of the rubber material are of great importance here. Tests have shown that on the same car, but with different tires, the length of the braking distance can vary up to three to five meters, and there is nothing to say about the quality of the coating. Try to compare braking on dry pavement and on ice.
As you can see, there are a lot of factors that affect the braking distance, and even more so the stopping distance, so the maximum concentration of attention behind the wheel is a guarantee safe ride. Check your brakes on time, don't talk on the phone while driving and may all your roads be kind!
Any motorist knows that often we are separated from an accident in just a fraction of a second. A car moving at a certain speed cannot freeze in place, as if rooted to the spot, after pressing the brake pedal, even if you have Continental tires, which traditionally occupy high places in the ratings, and brake pads with high brake pressure.
After pressing the brake, the car still overcomes a certain distance, which is called the brake or stopping way. So stopping distance is the distance traveled vehicle from the moment the brake system is applied to a complete stop. The driver must at least approximately be able to calculate the stopping distance, otherwise one of the basic rules of safe movement will not be observed:
- the stopping distance must be less than the distance to the obstacle.
Well, here such an ability as the driver’s reaction speed comes into play - the sooner he notices an obstacle and presses the pedal, the earlier car will stop.
The length of the braking distance depends on such factors:
- movement speed;
- quality and type of road surface - wet or dry asphalt, ice, snow;
- the condition of the tires and braking system of the vehicle.
Please note that such a parameter as the weight of the car does not affect the length of the braking distance.
The braking method is also of great importance:
- sharp pressing to the stop leads to uncontrolled skidding;
- gradual increase in pressure - used in a calm environment and with good visibility, in emergency situations does not apply;
- intermittent pressing - the driver presses the pedal several times to the stop, the car may lose control, but stops quickly enough;
- stepped pressing - works according to the same principle, the driver completely blocks and releases the wheels without losing contact with the pedal.
There are several formulas that determine the length of the stopping distance, and we will apply them for different conditions.
dry asphalt
The braking distance is determined by a simple formula:
From the course of physics, we remember that μ is the coefficient of friction, g is the acceleration of free fall, and v is the speed of the car in meters per second.
Imagine the situation: we are driving a VAZ-2101 at a speed of 60 km / h. At 60-70 meters we see a pensioner who, forgetting about any safety rules, rushed across the road after a minibus.
We substitute the data in the formula:
- 60 km/h = 16.7 m/s;
- the coefficient of friction for dry asphalt and rubber is 0.5-0.8 (usually 0.7 is taken);
- g = 9.8 m/s.
We get the result - 20.25 meters.
It is clear that such a value can only be for ideal conditions: good quality tires and brakes everything is fine, you braked with one sharp press and all the wheels, while not going into a skid and not losing control.
You can double-check the result using another formula:
S \u003d Ke * V * V / (254 * Fc) (Ke - braking coefficient, for passenger cars it equals one; Фс - adhesion coefficient with coating - 0.7 for asphalt).
IN this formula put the speed in kilometers per hour.
We get:
- (1*60*60)/(254*0.7) = 20.25 meters.
Thus, the length of the braking distance on dry pavement for passenger cars moving at a speed of 60 km / h, under ideal conditions, is at least 20 meters. And that's with hard braking.
Wet asphalt, ice, rolled snow
Knowing the coefficients of adhesion to the road surface, you can easily determine the length of the braking distance under various conditions.
Odds:
- 0.7 - dry asphalt;
- 0.4 - wet asphalt;
- 0.2 - packed snow;
- 0.1 - ice.
Substituting these data into the formulas, we obtain the following values for the length of the stopping distance when braking at 60 km/h:
- 35.4 meters on wet pavement;
- 70.8 - on packed snow;
- 141.6 - on ice.
That is, on ice, the length of the braking distance increases by 7 times. By the way, on our website there are articles about that, and. Also, safety during this period depends on right choice winter tires.
If you are not a fan of formulas, then on the net you can find simple calculators stopping distance, whose algorithms are based on these formulas.
Stopping distance with ABS
home ABS task- do not let the car go into an uncontrolled skid. The principle of operation of this system is similar to the principle of stepped braking - the wheels are not completely blocked and thus the driver retains the ability to drive the car.
Numerous tests show that with ABS brake shorter way to:
- dry asphalt;
- wet asphalt;
- rolled gravel;
- on the plastic sheet.
On snow, ice, or muddy soil and clay, braking performance with ABS is somewhat reduced. But at the same time, the driver manages to maintain control. It is also worth noting that the length of the braking distance largely depends on the settings of the ABS and the presence of EBD (brake force distribution system).
In short, the fact that you have ABS does not give you an advantage in winter time. The length of the braking distance can be 15-30 meters longer, but then you do not lose control of the car and it does not deviate from its route. And on the ice, this fact means a lot.
Motorcycle stopping distance
Learning how to properly brake or slow down on a motorcycle is not an easy task. You can brake front, rear or both wheels at the same time, engine braking or skidding is also used. If you brake incorrectly high speed you can very easily lose your balance.
The braking distance for a motorcycle is also calculated using the above formulas and is for 60 km / h:
- dry asphalt - 23-32 meters;
- wet - 35-47;
- snow, mud - 70-94;
- black ice - 94-128 meters.
The second digit is the skid braking distance.
Any driver or motorcyclist should know the approximate stopping distance of their vehicle when different speeds. When registering an accident, traffic police officers can determine the speed at which the car was moving along the length of the skid.
Probably most car owners know. Even if you have not measured the acceleration dynamics of your car, you probably looked at the factory specifications of your car, where the car manufacturer usually specifies the minimum possible time acceleration from 0-100 km/h. But now the question is: how long does it take to stop your car? Do you know it? We are sure not. But it turns out that the braking distance can be calculated quite easily using a simple formula. We'll tell you how it's done.
There is no such thing in the universe or matter that can stop instantly. Also, any car, when you press the brake pedal, may not immediately stop. The fact is that in order for a car or any object in our world to stop, it is necessary that it loses the energy that drives it. As a result, any car has a stopping distance that it travels from the moment the brake pedal is pressed to the moment it comes to a complete stop. That's what it is .
But in fact, the braking distance of any car depends not only on its characteristics and braking system, but also on the driver's reaction when the brake pedal is pressed. After all, in order to decide on the need to brake and press the brake pedal, it takes time, which, although minimal, is enough for the car to drive a rather long distance. This is especially important at high speeds, where in a fraction of a second the car travels a decent distance. So, in the end, in order to calculate the actual length of the braking distance, it is necessary to take into account not only the time and distance traveled by the car from the moment the driver presses the brake pedal to the moment the car stops, but also the time required to make a decision on braking. The fact is that when deciding on braking, we waste precious seconds. Here is an example:
- Response time: Before the driver presses the brake pedal, he must evaluate traffic situation and determine if braking is necessary. You also need to understand what kind of braking is needed - a complete stop of the car or a simple decrease in speed. Usually, according to numerous studies, most drivers need about 0.1 seconds to do this.
- Time required to press the brake pedal: After the driver has realized that he must brake, it takes about 0.8 seconds more to move his foot from the gas pedal to the brake pedal and press it.
In addition, even when the brake pedal is pressed, there is still a slight loss of time due to the fact that when the brake pedal is pressed, the car, as a rule, does not start to brake sharply. And in order for the car to really start to sharply reduce speed, it is necessary to increase the pressure on the brake pedal (the threshold time required for the required brake pressure in the braking system). Also, all cars have a different response time to the brake pedal pressed. Everything here, of course, depends on the design of the brake system and the availability of various electronics that control the car's brakes.
You will not believe it, but in order for the car to really start to slow down after pressing the brake pedal, it takes almost 1 second of time. Can you imagine how much it is when driving at high speed? In this extra second, you can travel a very long way.
What is the stopping distance formula?
In general, vehicle braking is divided into two types. For example, there is normal braking, and there is emergency braking, when you need to stop the car abruptly to avoid an accident.
When braking in everyday life, for example, if you want to stop the car at a traffic light, you usually depress the brake pedal much more smoothly and softly than if you need to completely stop the car in a parking lot in the yard. In this case, you do not apply the maximum braking force in the car. With such smooth and soft braking, as a rule, (braking distance) increases. Approximate braking distance at normal braking can be calculated using the following simple formula:
(Speed in km/h: 10) x (Speed in km/h: 10) = Stopping distance in meters
At emergency braking the brake pedal is usually fully depressed and full strength. Due to the higher braking force, the braking distance of the machine is usually reduced by about 2 times. Therefore, the stopping distance can also be calculated using the following formula:
(Speed in km/h: 10) x (Speed in km/h: 10) / 2 = Stopping distance in meters
Attention: The braking distance calculated using these formulas is only an approximate value and a hint for drivers. In fact, in reality, the braking distance can be either less or more. After all, the braking distance depends on the driver’s driving skills and experience, on the technical condition of the car, its design, brand, model, road condition, rubber tread condition and many other factors that directly affect the braking distance. But thanks to these formulas, you can roughly calculate the average stopping distance of a car at a certain speed. This will allow you to adjust your driving style, and will also be a good guide for novice drivers.
How to calculate the total stopping time and the final stopping distance?
As we have already said, in order to calculate the entire braking distance, you need to take into account the loss of time when the driver decides to brake (that is, the reaction time of the driver). To do this, you need to use a different formula that provides a more accurate estimate of the braking distance that the car will travel at the time the decision is made to stop. Here is the formula:
(Speed in km/h: 10) x 3 = reaction path in meters
As a result, by making the calculation according to the above formulas, you can calculate the approximate final stopping distance of your car at any speed. Here is an example. If you are driving your car at a speed of 50 km / h, then using the above formulas, calculate the following values:
- Braking distance when making a decision about braking at this speed (reaction to the traffic situation + decision to brake + the time required to move the foot from the gas pedal to the brake pedal, as well as the response time of the brake system to the depressed brake pedal) will be somewhere (50/10) x 3 = 15 meters. That is, while you decide to brake at a speed of 50 km / h, your car will travel 15 meters.
- Stopping distance under normal braking(from the moment you press the brake pedal to the moment the car stops) will be about (50/10) x (50/10) = 25 meters.
- During emergency braking the braking distance, as we have already noted, is reduced by about half. Accordingly, the calculation of the braking distance of a car that is moving at a speed of 50 km / h will look like this: (50/10) x (50/10) / 2 = 12.5 meters.
- As a result, we can now calculate the actual final stopping distance of the car. So, with normal (not sharp, but normal) braking, the final braking distance will be about 40 meters. In case of emergency braking - at least 28 meters.
Note: Please note that if the speed of the car is only twice as high, its final braking distance will increase four times!!!
That is, the opinion that when the speed of the car is doubled, the braking distance only doubles, is pure water a myth among many motorists. So keep that in mind when you get behind the wheel. The most surprising thing is that even many experienced drivers do not know about it.
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Example for calculating braking and stopping distances |
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Speed, in km/h |
The path taken by the car during the driver's reaction, in meters |
Braking distance, in meters (from the moment you press the brake pedal to a complete stop of the car) |
Final stopping distance, in meters |
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6,25 |
13,75 |
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What factors affect braking and stopping distance?
Of course, is the speed of the car with which it moves on the road. The quality of the brake system installed on the car also affects the braking distance. Including important role, undoubtedly, the condition of the road also plays a role (snow, ice, quality of asphalt / concrete, cracks in the road surface, leaves, puddles, etc.). And of course, do not forget about the condition of the tires of the car. Indeed, in certain cases worn rubber will greatly increase the stopping distance of the car, as it will not be able to transmit normal braking power to the road surface, unlike new tires that have normal grip.
It is also clear that on wet surfaces the braking distance of the car is greater than on dry pavement.
Do not forget about the level of driver training. Particularly important, as we have learned, for the final stopping distance is the speed of the driver's reaction to a traffic situation that requires the car to stop. But the speed of reaction behind the wheel depends not only on driving experience. For example, did you know that when you get behind the wheel in a sleepy state (did not get enough sleep, are tired or have been driving for a long time), the reaction speed can slow down by almost half compared to the reaction speed of a well-rested driver.
In general, the speed of decision-making behind the wheel (speed of reaction) is influenced by many factors: the age of the driver, alcohol or hangover, the use of certain medications, and the general state of health. So, with many chronic diseases, the reaction rate of many drivers is significantly reduced. Therefore, all these factors seriously affect the stopping distance of the car.
When a novice driver gets behind the wheel, after two or three trips he is convinced of personal experience: stopping distance is not always the same. In some situations, this distance is vital, so everyone must be able to calculate the stopping distance of their car.
In theory, stopping distance is the distance traveled by a vehicle from the moment you press the brake pedal to a complete stop. This figure depends on several factors: speed, road surface, wear of the brake system, type of tires and their condition. To calculate the stopping distance, the formula S = Ke x V x V / (254 x Fc) is used. The designation S is the length of the braking distance in meters, Ke is the braking coefficient (y passenger car this indicator is equal to one), V is the speed at the beginning of braking (in km/h), Фc is the coefficient of adhesion to the road. The latter value depends on the weather: for dry asphalt it is 0.7, for wet asphalt - 0.4, for rolled snow - 0.2, and for ice - 0.1.
Do not forget that by depressing the brake pedal to the limit, you can completely block the wheels, then the car will become uncontrollable. Be careful on the road, observe moderate speed mode, and you can protect yourself, your passengers and other road users from traffic accidents.
