It may happen that the integrity of the car body and the safety of its passengers will depend on the length of the braking distance. A car at speed simply cannot stop abruptly after pressing the brake, even if they are standing on it quality tires And efficient system braking. After the brake pedal is pressed, the car in any case covers a certain distance, and this distance is called - braking distances.
The driver must constantly calculate the braking distance in accordance with one of the traffic safety rules, which states that the braking distance must be less than the distance to the obstacle.
In this situation, everything depends on the reaction and skill of the driver; the sooner he presses the brake and more correctly calculates the length of the braking distance, the sooner and more successful than a car will slow down.
Braking distance of a car at a speed of 60 km/h
Body deformation in a collision at a speed of 60 km/h
Stopping distance also depends not only on the driver, but also on other related factors: the quality of the road, speed, weather conditions, states brake system, brake system devices, car tires and many others.
note that weight passenger car does not affect the braking distance. This is due to the fact that the weight of the car increases the inertia of the car when braking, thereby preventing braking, but increases the grip of the tires on the road due to the increased weight of the car.
These physical properties compensate each other, while having virtually no effect on the braking distance.
The braking speed directly depends on the braking method. Hard brake all the way, will lead to the car skidding or skidding (if the car is not equipped with an ABS system).
Gradual pressing on the pedal is used when on the road good visibility and a calm environment, it is not suitable for emergency situations. When pressed intermittently You can lose control, but you can stop quickly. It's also possible stepped pressing(similar in effect to ABS system).
There are special formulas that allow you to determine the length of the braking distance. We will try to calculate the formula using different conditions, depending on the type of road surface.
Formula for determining braking distance
Braking distance on dry asphalt
Let's remember physics lessons, where ? is the friction coefficient, g is the acceleration of free fall, and v– vehicle speed in meters per second.
The situation is as follows: the driver is driving Lada car whose speed is 60 km/h. Literally 70 meters away is an elderly woman who, forgetting about safety rules, is quickly catching up minibus(standard situation for Russia).
Let's use this very formula: 60 km/h = 16.7 m/sec. Dry asphalt has a friction coefficient of 0.7, g – 9.8 m/s. In fact, depending on the composition of the asphalt, it is from 0.5 to 0.8, but let’s take the average value.
The result obtained from the formula is 20.25 meters. Naturally, this value is only appropriate for ideal conditions when the machine is equipped with high quality tires And brake pads, the braking system is working properly, when braking you do not skid and do not lose control, due to many other idealized factors that do not occur in nature.
Also, to double-check the result, there is another formula for determining braking distance:
S = Ke * V * V / (254 * Fs), where Ke is the braking coefficient, for passenger cars it is equal to one; Fs – coefficient of adhesion with coating 0.7 (for asphalt).
We substitute the vehicle speed in km/h.
It turns out that the braking distance is 20 meters for a speed of 60 km/h (for ideal conditions), if the braking is sharp and without skidding.
Braking distance on surface: snow, ice, wet asphalt
BMW cars on test
The adhesion coefficient helps to indicate the length of the stopping distance at different road conditions. Odds for different road surfaces:
- Dry asphalt – 0.7
- Wet asphalt – 0.4
- Rolled snow – 0.2
Let's try to substitute these values into the formulas and find the braking distance values for the road surface at different times of the year and under different weather conditions:
- Wet asphalt – 35.4 meters
- Rolled snow – 70.8 meters
- Ice – 141.6 meters
It turns out that on ice the braking distance is almost seven times higher, relative to dry asphalt (as well as the substituted coefficient). The braking distance is influenced by the quality winter tires, physical properties.
Testing has shown that with the ABS system, the stopping distance is significantly reduced, but still in case of ice and snow ABS does not affect, but rather worsens braking performance when compared with a braking system without ABS. However, in ABS, to a large extent, everything depends on the settings and the presence of a brake force distribution system (EBD).
The advantage of ABS is winter time – full control over the control of the car, which minimizes the occurrence of uncontrolled skidding when braking. Principle ABS operation similar to performing step braking on cars without ABS.
The ABS system reduces braking distance by: dry and wet asphalt, rolled gravel, markings.
On ice and compacted snow, the use of ABS increases the braking distance by 15 - 30 meters, but allows you to maintain control over the car, without the car going into a skid. This fact should be taken into account.
How to brake on a motorcycle?
Braking correctly on a motorcycle is quite a difficult task. You can slow down rear wheel, front, or two, skid or engine. If you brake incorrectly high speeds you may lose your balance. In order to calculate the braking distance of a motorcycle at 60 km/h, we also substitute the data into the formula. Taking into account the different braking coefficient and friction coefficient.
Motorcycle braking distance
- Dry asphalt: 23 - 33 meters
- Wet asphalt: 35 - 46 meters
- Mud and snow: 70 - 95 meters
- Ice: 95 - 128 meters
The second indicator is the braking distance when the motorcycle is skidding.
Any vehicle owner should know and be able to calculate the braking distance, and it is better to do this visually.
It should be remembered that if a traffic accident occurs along the length of the skid that will remain on the road surface, you can determine the speed of the vehicle before colliding with an obstacle, which may indicate an excess permissible speed driver and make him the culprit of the incident.
Braking distance is the distance it takes for a vehicle to come to a complete stop from the moment the braking system begins to operate.
In everyday life, this term is often confused with stopping distance, but braking distance and stopping distance are different concepts. In the latter case, the distance elapsed from the moment the driver realized the need to brake to a speed of 0 km/h is taken into account. The braking distance is part of the stopping distance. 
What does braking distance depend on?
The indicator under consideration is not a constant value and can vary for a number of reasons. All factors influencing the braking distance can be divided into two large groups: driver-dependent and driver-independent. Reasons beyond the control of the person driving include:
- road condition;
- weather.
It is easy to guess that in rain, snow or ice, the distance required to stop a car will be greater than on dry asphalt. Braking will take a long time even when driving on smooth asphalt, to which stone chips have not been added. Here the wheels have nothing to catch on, unlike rough surfaces.
Note: it is worth noting that poor quality of the road (potholes, potholes) does not lead to an increase in the distance required to stop. The human factor plays a role here. Trying to save the suspension, drivers rarely develop high speed on similar roads. Accordingly, the braking distance here is minimal.
Factors depending on the driver or owner of the car:
- brake condition;
- system design;
- type of tires;
- vehicle load;
- movement speed.
The fact that the length of a car’s braking distance directly depends on the serviceability of the braking system does not require proof. A car with a malfunctioning brake circuit or worn out pads will never be able to stop as quickly as a working vehicle. 
A lot depends on the design of the brake units. Modern cars, equipped with rear disc brakes and braking assistance systems, have much better traction and a shorter braking period.
In turn, the presence of EBD with ABS does not always help reduce the distance required to stop. On dry hard surfaces, where wheel locking occurs only with very intense braking, the system actually shortens the braking distance. However, on bare ice, “smart” electronic assistant starts to reset braking force even when lightly pressing the brake pedal. At the same time, the car retains controllability, but its braking distance increases significantly.
What determines the rate of deceleration? Of course, it depends on the type of tires. So, on bare, albeit frozen, asphalt, as well as in slushy snow, the so-called brakes are best. "Velcro" - winter tires, not equipped with spikes. In turn, in icy conditions and snowy roads The most effective is studded rubber.
An important factor influencing the size of the stopping distance is the speed and load of the machine.
It is clear that a lightweight car at a speed of 60 km/h will stop faster than a truck loaded to capacity and moving at a speed of 80-100 km/h. The latter will not be allowed to stop quickly because the speed and inertia are too high for him.
When and how measurements are taken
Braking distance calculations may be required in the following cases:
- technical testing of the vehicle;
- checking the capabilities of the car after modifying the brakes;
- forensic examination.
As a rule, the formula S=Ke*V*V/(254*Fs) is used in calculations. Here S is the braking distance; Ke – braking coefficient; V₀ — speed at the start of braking; Фс – coefficient of adhesion to the coating.
The coefficient of road adhesion varies depending on the condition of the surface and is determined according to the following table:
| Road condition | Fs |
|---|---|
| Dry | 0.7 |
| Wet | 0.4 |
| Snow | 0.2 |
| Ice | 0.1 |
The Ke coefficient is a static value and is unity for all the most common passenger vehicles.
Example: how to calculate the braking distance of a car when the speedometer shows 60 km/h in the rain? Given: speed 60 km/h, braking coefficient – 1, adhesion coefficient – 0.4. We count: 1*60*60/(254*0.4). As a result, we get the figure 35.4, which is the braking distance in meters.
The table shows how many meters the car will continue to move until it comes to a complete stop. It should be taken into account that no other indicators are taken into account (turns, potholes on the road, oncoming traffic, etc.). It is doubtful that in real conditions on an icy road, a car will be able to slide for a kilometer without encountering a pole or bump stop.
| Speed | Dry | Rain | Snow | Ice |
|---|---|---|---|---|
| km/h | meters | |||
| 60 | 20,2 | 35,4 | 70,8 | 141,7 |
| 70 | 27,5 | 48,2 | 96,4 | 192,9 |
| 80 | 35,9 | 62,9 | 125,9 | 251,9 |
| 90 | 45,5 | 79,7 | 159,4 | 318,8 |
| 100 | 56,2 | 98,4 | 196,8 | 393,7 |
| 110 | 68 | 119 | 238,1 | 476,3 |
| 120 | 80,9 | 141,7 | 283,4 | 566,9 |
| 130 | 95 | 166,3 | 332,6 | 665,3 |
| 140 | 110,2 | 192,9 | 385,8 | 771,6 |
| 150 | 126,5 | 221,4 | 442,9 | 885,8 |
| 160 | 143,9 | 251,9 | 503,9 | 1007,8 |
| 170 | 162,5 | 284,4 | 568,8 | 1137,7 |
| 180 | 182,2 | 318,8 | 637,7 | 1275,5 |
| 190 | 203 | 355,3 | 710,6 | 1421,2 |
| 200 | 224,9 | 393,7 | 787,4 | 1574,8 |
We found an interesting calculator that not only calculates the indicator depending on the speed and condition of the road, but also clearly shows the whole process. Located .
How to increase the intensity of deceleration
From the above, it became clear what is called the braking distance and what this indicator depends on. However, is it possible to reduce the distance required to stop a car? Maybe! There are two ways to do this - behavioral and technical. Ideally, the driver combines both methods.
- Behavioral method - you can reduce the braking distance if you choose a low speed on slippery and wet roads, take into account the degree of load of the car, correctly calculate the braking capabilities of the car depending on its condition and model year. Thus, a Moskvich developed in 1985 will not be able to brake as effectively as a modern one. Hyundai Solaris", not to mention more respectable and technologically advanced models.
- Technical method - a method of enhancing braking capabilities, based on increasing the power of the braking system and the use of auxiliary mechanisms. Manufacturers of modern vehicles actively use such methods of improving brakes, equipping their products anti-lock systems, braking assistance systems, using more efficient brake discs, pads.
It should be remembered that reducing the time required to stop is one of the ways to ensure a safe trip. Therefore, every driver must constantly monitor technical condition his " iron horse", promptly maintain and repair the braking system. In addition, it is important to choose the driving speed taking into account the surrounding situation: time of day, road condition, car model, etc.
It is not for nothing that the recommended speed for vehicles is 60 km/h on the signs, because by adhering to this figure, the driver can make safe movement and stop on time. This is especially true when an unforeseen situation arises where you need to apply emergency braking or a sharp maneuver. If you still need to brake, then the braking distance, in in this case, will be about 25 meters, but the figure is influenced by many aspects, such as: the weight of the car, the quality of the tires, serviceability and much more. Let's look at this in more detail.
If the road surface, namely asphalt, is dry, then braking will be minimal because traction remains excellent. Wet asphalt will increase braking distances due to water's ability to reduce friction. If we consider another road, for example, where there is earth on the surface, then the path also increases, the same can be said about concrete, due to its smoothness. In numbers, this is not 25, but already 125 meters, again at 60 kilometers per hour.
Application of ABS
This system stands for Anti-lock Braking System, and it is used to reduce the braking distance. How does it work? It turns out that when the driver depresses the brake pedal as much as possible, the system prevents the wheels from completely locking. Otherwise, sliding occurs, and there will be no talk of controllability.
In any case, you need to monitor the serviceability of the brake system, because it may not even help.
Vehicle and tire weight
It will be very difficult for the car to cope with large mass, so you should never forget to keep your distance. It is best if the driver prepares for the trip in advance and knows the braking distance of his car. An equally important role is played by the tread pattern, the presence of studs, seasonality, etc., in general, so that the tires meet many requirements. This is especially true and at the same time dangerous when the tire is already worn out and worn out, and the road is wet. In this case, the braking distance will be very long and may lead to an accident.
Every driver has at least once found himself literally a couple of seconds away from an accident when it is vitally important to have time to brake. However, the car cannot stand rooted to the spot on command. The distance that it travels from the moment it starts braking until it comes to a complete stop is called the braking distance. To be able to estimate the braking distance, you need to ensure that it is always less than the distance to the obstacle in the way.
The length of the braking distance depends on many different factors. This includes the driver’s reaction, the level of performance of the car’s braking system, and external factors, such as the track material and weather conditions. And of course, the speed of the car at the moment of braking plays a decisive role. The question arises - how to calculate the braking distance of a car under all these conditions? Sufficient for general calculations three main factors - braking coefficient (Ke), speed (V) and coefficient of adhesion (Fs) with the road.
Formula for calculating the braking distance of a car
The formula from the table that calculates the braking distance looks like this: S=Ke*V*V/(254*Fs). The braking coefficient of a conventional light car equals one. The adhesion coefficient on a dry surface will be 0.7. For example, let's take the case when a car is moving on a dry road at a speed of 60 km/h. Then the braking distance will be equal to 1*60*60/(254*0.7)=20.25 meters. On ice (Fs=0.1) braking will last seven times longer - 141.7 meters!
Based on the result, we see how much the braking distance of a car from the table depends on the condition of the highway and weather conditions.
The length of the braking distance is inversely proportional to the coefficient of adhesion to the road. Simply put, the worse the road “holds”, the longer car slows down. Let's look at the changes in the coefficient (Fs) in more detail:
- with dry asphalt - 0.7;
- on wet asphalt - 0.4;
- if the snow is rolled - 0.2;
- icy road - 0.1.
These numbers allow us to see how stopping distances will change depending on conditions. As already mentioned, at a speed of 60 km/h on a dry road the car will brake in 20.25 meters, and on ice - 141.7. On wet track The braking distance will be 35.4 meters, and on snowy conditions - 70.8.
Types of braking
Types of braking
It is also worth considering that the method of braking plays a big role:
- A sharp press can send the car into an uncontrolled skid.
- Gradually pressing the pedal will work if there is good visibility and time to spare, but it cannot be used in an emergency situation.
- Intermittent braking with several presses of the pedal to the stop will allow you to quickly stop the car, but is also fraught with loss of control.
- Pressing in steps will allow you to lock the wheels without losing contact with the pedal.
Braking with ABS
The ABS system works precisely on the principle of stepped braking, and its main task is to prevent the car from going into an uncontrolled skid. ABS does not completely block the wheels, thereby leaving the driver in control of the vehicle's movement. Extensive testing has shown that ABS will shorten stopping distances on dry or wet pavement, and also works great on gravel. But in other conditions the system partially loses its value.
IN winter conditions ABS will increase the braking distance by 15-30 meters when driving on snow or ice. At the same time, the system will leave the driver control of the car, which can be critically important when driving on ice.
Friction table at different speeds
Remember weak points ABS - muddy earth and clay. The braking distance may also be longer with them than with fully “manual” braking. But control over the car will also remain.
How to determine the speed of a car based on the braking distance?
In cases where it was still not possible to brake in time, it is necessary to determine at what speed the vehicle was moving at the moment the braking began. The general formula for calculating the “starting” braking speed looks like this: V = 0.5*t3*j + √2*S*j. In this case, the following factors play a role:
- tЗ— the rise time of the deceleration of the machine. Measured in seconds;
- j- slowing down the car when braking. Measured in m/s2. According to GOST on a dry route j=6.8 m;
- s2, and on wet - 5 m/s2;
- S— the length of the braking trail.
Let's take conditions in which tЗ = 0.3 seconds, the braking trail is 20 meters, and the track is dry. Then the speed is 0.5*0.3*6.8 + √2*20*6.8 = 1.02 + 19.22 = 20.24 m/s = 72.86 km/h.
Basically, three methods are used to determine the speed at the beginning of braking:
- Determination by braking distance.
- Determination by the law of conservation of momentum.
- Determination by car deformation.
The advantages of the first method are simplicity and speed, a large number of studies, and accurate results. The good thing about the second method is that it can be used when there are no signs of braking, it gives an accurate result and is useful when colliding with stationary cars. The third differs in that it takes into account the energy consumption for the deformation of the machine.
Each method also has its own disadvantages. In the first case, it is impossible to use in the absence of tire marks. In the second there are cumbersome calculations, and in the third there are large volumes of what needs to be taken into account and low accuracy of calculations.
Any motorist knows that often we are separated from an accident by literally a split second. A car moving at a certain speed cannot freeze in place, rooted to the spot, after pressing the brake pedal, even if you have Continental tires, which traditionally occupy high places in ratings, and brake pads with a high brake pressure ratio.
After pressing the brake, the car still covers a certain distance, which is called the braking or stopping distance. Thus, the braking distance is the distance covered vehicle from the moment the brake system is activated until 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 an ability such as the driver’s reaction speed comes into play - the sooner he notices an obstacle and presses the pedal, the before the car will stop.
The length of the braking distance depends on the following factors:
- movement speed;
- quality and type of road surface - wet or dry asphalt, ice, snow;
- condition of the tires and brake system of the car.
Please note that such a parameter as the weight of the car does not affect the length of the braking distance.
The method of braking is also of great importance:
- sharp pressing all the way leads to an uncontrolled skid;
- gradual increase in pressure - used in a calm environment and with good visibility, in emergency situations not applicable;
- intermittent pressing - the driver presses the pedal all the way several times, the car may lose control, but stops quickly enough;
- stepped pressing - it works on the same principle, the driver completely blocks and releases the wheels without losing contact with the pedal.
There are several formulas used to 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:
We remember from the physics course that μ is the coefficient of friction, g is the acceleration of gravity, and v is the speed of the car in meters per second.
Let's imagine the situation: we are driving a VAZ-2101 at a speed of 60 km/h. About 60-70 meters away we see a pensioner who, forgetting about any safety rules, rushed across the road to get a minibus.
Substitute the data into the formula:
- 60 km/h = 16.7 m/sec;
- the friction coefficient for dry asphalt and rubber is 0.5-0.8 (usually 0.7);
- 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 are fine, you braked with one by pressing hard and all wheels, but did not skid and did not lose control.
You can double-check the result using another formula:
S=Ke*V*V/(254*Fc) (Ke is the braking coefficient, for passenger cars it is equal to one; Fs is the coefficient of adhesion with the coating - 0.7 for asphalt).
The speed in kilometers per hour is substituted into this formula.
We get:
- (1*60*60)/(254*0.7) = 20.25 meters.
Thus, the braking distance on dry asphalt for passenger cars moving at a speed of 60 km/h under ideal conditions is at least 20 meters. And this is subject to sudden braking.
Wet asphalt, ice, compacted snow
Knowing the coefficients of adhesion with road surface, you can easily determine the braking distance under different conditions.
Odds:
- 0.7 - dry asphalt;
- 0.4 - wet asphalt;
- 0.2 - compacted snow;
- 0.1 - ice.
Substituting these data into the formulas, we obtain the following values for the stopping distance when braking at 60 km/h:
- 35.4 meters on wet asphalt;
- 70.8 - on compacted snow;
- 141.6 - on ice.
That is, on ice the braking distance increases 7 times. By the way, on our website there are articles about that and. Also, safety during this period depends on the right choice winter tires.
If you are not a fan of formulas, then on the Internet you can find simple braking distance calculators, the algorithms of which are based on these formulas.
Stopping distance with ABS
The main task of ABS is to prevent the car from going into an uncontrolled skid. The principle of operation of this system is similar to the principle of step braking - the wheels are not completely blocked and thus the driver remains able to control the car.
Numerous tests demonstrate that with ABS brake the path is shorter by:
- dry asphalt;
- wet asphalt;
- rolled gravel;
- on plastic markings.
On snow, ice or on muddy soil and clay, the braking efficiency of ABS is slightly reduced. But at the same time, the driver manages to maintain controllability. It is also worth noting that the length of the braking distance largely depends on the ABS settings and the presence of EBD - brake force distribution system).
In short, the fact that you have ABS does not give you an advantage in the winter. The braking distance may be 15-30 meters longer, but you do not lose control of the car and it does not deviate from its route. And on ice this fact means a lot.
Motorcycle braking distance
Learning to brake or brake properly on a motorcycle is not an easy task. You can brake with the front, rear or both wheels at the same time; engine or skid braking 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;
- icy conditions - 94-128 meters.
The second number is the skid braking distance.
Any driver or motorcyclist should know the approximate braking distance of his vehicle at different speeds. When registering an accident, traffic police officers can determine the speed at which the car was moving based on the length of the skid.
