Deceleration rise time table. B.M

19.10.2019

Brake system

After each traffic accident, the speed of the vehicle before and at the moment of impact or collision is necessarily determined. This value is so important for several reasons:

The most frequently violated point of the traffic rules is the excess of the maximum permissible speed, and thus it becomes possible to determine the probable culprit of the accident.
Also, the speed affects the braking distance, and hence the ability to avoid a collision or collision.

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Determination of vehicle speed by braking distance

The braking distance is usually understood as the distance that a vehicle travels from the start of braking (or, to be more precise, from the moment the brake system is activated) to a complete stop. The general, non-detailed formula, from which it is possible to derive a formula for calculating the speed, looks like this:

Va = 0.5 x t3 x j + √2Sy x j= 0.5 0.3 5 + √2 x 21 x 5 = 0.75 +14.49 = 15.24m/s = 54.9 km/h where: in the expression √2Sy x j, where:

Va is the initial speed of the vehicle, measured in meters per second;
t3– vehicle deceleration rise time in seconds;
j– steady vehicle deceleration during braking, m/s2; note that for wet pavement - 5 m / s2 according to GOST 25478-91, and for dry pavement j = 6.8 m / s2, hence the initial speed of the car with a “skid” of 21 meters is 17.92 m / s, or 64 .5km/h
Su- the length of the brake track (skid), also measured in meters.

The process of determining speed during an accident is described in more detail in a wonderful article. Accounting for potential deformation when determining the vehicle speed at the time of an accident. You can download it in PDF format. Authors: A.I. Money, O.V. Yaksanov.

Based on the above equation, we can conclude that the stopping distance is primarily affected by the speed of the car, which, with the other known values, is easy to calculate. The most difficult part of calculating this formula is the exact determination of the coefficient of friction, since its value is influenced by a number of factors:

type of road surface;
weather conditions (when the surface is wetted with water, the coefficient of friction decreases);
tire type;
tire condition.

For an accurate calculation result, it is also necessary to take into account the features of the braking system of a particular vehicle, for example:

material, as well as workmanship of brake pads;
diameter of brake discs;
functioning or malfunction of electronic devices that control the brake system.

Brake track

After a fairly quick activation of the brake system, prints remain on the road surface - brake marks. If the wheel is completely locked during braking and does not rotate, solid marks remain (sometimes called the “skid mark”), which many authors urge to consider as the result of the maximum possible pressure on the brake pedal (“brake to the floor”). In the case when the pedal is not fully pressed (or there is some kind of defect in the brake system), there are as if “blurred” tread prints on the road surface, which are formed due to incomplete blocking of the wheels, which retain the ability to rotate during such braking.

stopping way

The stopping distance is the distance that a certain vehicle travels from the time the driver detects a threat to the stop of the car. This is precisely the main difference between the braking distance and the stopping distance - the latter includes both the distance that the car covered during the time the brake system was activated, and the distance that was covered during the time it took the driver to recognize the danger and react to it. Driver reaction time is affected by the following factors:

position of the driver's body;
psycho-emotional state of the driver;
fatigue;
some diseases;
alcohol or drug intoxication.

Determination of speed based on the law of conservation of momentum

It is also possible to determine the speed of the car by the nature of its movement after a collision, and also, in the event of a collision with another vehicle, by the movement of the second car as a result of the transfer of kinetic energy from the first. Especially often this method is used in collisions with stationary vehicles, or if the collision happened at an angle close to a straight line.

Determination of vehicle speed based on the obtained deformations

Only a very small number of experts determine the speed of the car in this way. Although the dependence of vehicle damage on its speed is obvious, there is no single effective, accurate and reproducible method for determining the speed from the obtained deformations.

This is due to the huge number of factors that affect the formation of damage, as well as the fact that some factors simply cannot be taken into account. The following can influence the formation of deformations:

the design of each particular vehicle;
features of cargo distribution;
the life of the car;
the quantity and quality of body work carried out by the vehicle;
metal aging;
vehicle design modifications.

Determination of speed at the time of collision (collision)

The speed at the time of the collision is usually determined from the brake wake, but if this is not possible for a number of reasons, then approximate speed figures can be obtained by analyzing the injuries sustained by the pedestrian and the damage resulting from the collision with the vehicle.

For example, the speed of a car can be judged by the features of a bumper fracture.- an injury specific to a car collision, which is characterized by the presence of a transverse splinter fracture with a large bone fragment of an irregular rhomboid shape on the side of impact. Localization when hit by a car bumper - the upper or middle third of the lower leg, for a truck - in the thigh area.

It is generally accepted that if the speed of the vehicle at the moment of impact exceeded 60 km/h, then, as a rule, an oblique or transverse fracture occurs, but if the speed was below 50 km/h, then a transverse fragmental fracture is most often formed. In a collision with a stationary car, the speed at the moment of impact is determined based on the law of conservation of momentum.

Analysis of methods for determining the speed of a car in an accident

Following the brake

Advantages:

relative simplicity of the method;
a large number of scientific papers and compiled methodological recommendations;
sufficiently accurate result;
the ability to quickly obtain the results of the examination.

Flaws:

in the absence of tire tracks (if the car, for example, did not slow down before the collision, or the features of the road surface do not allow measuring the skid mark with sufficient reliability), this method is impossible;
does not take into account the impact of one vehicle during a collision on another, which can.

According to the law of conservation of momentum

Advantages:

the ability to determine the speed of the vehicle even in the absence of signs of braking;
with careful consideration of all factors, the method has a high reliability of the result;
ease of use of the method in cross-collisions and collisions with stationary vehicles.

Flaws:

the lack of data on the mode of movement of the vehicle leads to an inaccurate result;
compared with the previous method, more complex and cumbersome calculations;
the method does not take into account the energy spent on the formation of deformations.

Based on the resulting deformities

Advantages:

takes into account the energy costs for the formation of deformations;
does not require brake marks.

Flaws:

doubtful accuracy of the results obtained;
a huge number of factors taken into account;
often the impossibility of determining many factors;
lack of standardized reproducible determination methods.

In practice, two methods are most often used - determining the speed on the trail of braking and based on the law of conservation of momentum. When using these two methods at the same time, the most accurate result is ensured, since the methods complement each other.

The remaining methods for determining the speed of a vehicle have not received significant distribution due to the unreliability of the results obtained and/or the need for cumbersome and complex calculations. Also, when assessing the speed of a car, the testimony of witnesses to the incident is taken into account, although in this case it is necessary to remember the subjectivity of the perception of speed by different people.

To some extent, analysis of video from surveillance cameras and video recorders can help to understand the circumstances of the incident and, as a result, get a more accurate result.

Page 1

The value of the vehicle deceleration (ј / m/s2) is established by conducting an investigative experiment in the road conditions of the scene of the incident or similar to it.

If the experiment is not possible, it can be determined from the reference data of the experimental and calculated values of the vehicle deceleration parameters. Either it is accepted as a normative one, established by the Rules of the Road of the Russian Federation, in accordance with the requirements of GOST R 51709-2001 “Vehicles. Safety requirements for technical condition and methods of verification.

Determination of the vehicle deceleration value is also possible by calculation using formulas known in expert practice, the main part of which was developed by V.A. Bekasov and N.M. Christie (TsNIISE).

▪ When driving a braked vehicle with wheels blocked:

in the general case (2.1)

on a horizontal line

ј = g ∙ φ (2.2)

▪ When the vehicle rolls freely by inertia (coasting):

in general

(2.3)

on a horizontal line

▪ When braking the vehicle with the wheels of the rear axle only:

in the general case (2.5)

on a horizontal section (2.6)

where g is the free fall acceleration, m/s2;

δ1 - coefficient of accounting for inertia of rotating unbraked wheels;

jH - steady-state deceleration for a technically sound vehicle when braking with all its wheels (taken according to reference data or calculated using formula 2.2), m/s2;

jK - deceleration of the vehicle during free rolling (determined by formula 2.4) m/s2;

a - distance from the center of gravity of the vehicle to the axis of its front wheels, m;

b - distance from the center of gravity of the vehicle to the axis of its rear wheels, m;

L - wheelbase of the vehicle, m;

hц - the height of the center of gravity of the vehicle above the supporting surface, m.

For motorcycles, cars and light trucks - δ1 ≈ 1.1, for loaded trucks and wheeled tractors - δ1 ≈1.0.

▪ When braking the vehicle with only the front wheels:

in the general case (2.7)

on a horizontal section (2.8)

Here, the definition and choice of parameters δ2, jH jK are similar to those indicated in the previous paragraph, with the exception of wheeled tractors. For them in this case δ2, = 1.1.

▪ When driving a vehicle with unbraked trailers (sidecar wheel) and a fully braked tractor (motorcycle):

in the general case (2.9)

on a horizontal section (2.10)

where: G is the total mass of the vehicle, kg;

Gnp - gross weight of the trailer (trailers) of the vehicle, kg.

For vehicles without load δnp ≈1.1, with load δnp ≈ 1.0

▪ When the vehicle is moving with unbraked trailers (sidecar wheel) and the tractor is braked only by the rear wheels or only by the front wheels:

in the general case (2.11)

on a horizontal section (2.12)

here j1 - deceleration, determined respectively by formulas (2.6) or (2.8);

δpr is the coefficient for taking into account the inertia of the rotating unbraked wheels of trailers (with the same values as in the previous paragraph).

▪ When oiling part of the wheel brakes:

in the general case (2.13)

on a horizontal section (2.14)

where: G" - the mass of the vehicle attributable to the wheels, except for wheels with oily brakes, kg;

G" is the mass of the vehicle on wheels with oiled brakes, kg.

▪ When the vehicle moves with a skid without braking: in general

Calculation of performance indicators of buses on the route "Mozyr - Gostov"
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"...steady deceleration" - the average value of deceleration during the braking time from the end of the time period of the increase in deceleration to the beginning of its decline at the end of braking;..."

Source:

Decree of the Government of the Russian Federation of September 10, 2009 N 720 (as amended on October 6, 2011) "On approval of the technical regulation on the safety of wheeled vehicles"

- one of the main classification features of a vehicle that determines its purpose and overall design ...
Forensic Encyclopedia
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Glossary of business terms
- forced detention of a vehicle on the basis of a decision of a judicial authority, carried out, for example, in order to ensure civil law ...
Big Economic Dictionary
- ".....
Official terminology
- "... 1) the owner of the vehicle - a person who owns the vehicle on the right of ownership or on another legal basis;..." Source: Federal Law of 01.07 ...
Official terminology
- "..." defect" - each individual non-compliance of the vehicle with the established requirements;..." Source: Decree of the Government of the Russian Federation of 10.09 ...
Official terminology
- a measure to ensure proceedings in cases of violation of certain traffic rules ...
Administrative law. Dictionary-reference
- forced detention of a vehicle by a court decision, carried out to ensure legal ...
Glossary of business terms
- 1. the mass of passengers and goods in the vehicle and intended for transportation 2 ...
Big Economic Dictionary
- ".....
Official terminology
- "..." vehicle base" - the distance between the vertical transverse plane passing through the axis of the front wheels and the vertical transverse plane passing through the axis of the rear wheels;.....
Official terminology
- "...Year of manufacture: calendar year in which the vehicle was manufactured..." Source: "VEHICLES. MARKINGS. GENERAL SPECIFICATIONS...
Official terminology
- "... LOADING CAPACITY OF A VEHICLE - the mass of cargo that this vehicle is designed to carry .....
Official terminology
- ".....
Official terminology
- ".....
Official terminology
- "..." stability of the vehicle during braking" - the ability of the vehicle to move during braking within the traffic corridor;..." Source: Decree of the Government of the Russian Federation of 10.09 ...
Official terminology

"Sustained deceleration when braking a vehicle" in books

From the book Use of other people's property the author Panchenko T M

Article 637

Vehicle rental

From the book Organization Expenses: Accounting and Tax Accounting author Utkina Svetlana Anatolievna

Vehicle rental The cost of compensating employees for the use of their personal vehicles for business trips is included in other expenses related to production and distribution. At the same time, the norms of expenses for these purposes are established

2. 5. Vehicle selection

From the book Logistics author Savenkova Tatyana Ivanovna

2. 5. Choice of vehicle The choice of transport is decided in relation to other logistics tasks: creating and maintaining an optimal level of stocks, choosing the type of packaging, etc. The choice of vehicles will be influenced by: the nature of the cargo (weight, volume,

From the book Civil Code of the Russian Federation the author GARANT

Detention of a vehicle

From the author's book

Detention of the vehicle Article 27.13. Detention of a vehicle 1. In case of violations of the rules for operating, using a vehicle and driving a vehicle of the appropriate type, provided for in Articles 11.26, 11.29, part 1 of Article

author State Duma

From the book Code of the Russian Federation on Administrative Offenses (CAO RF) author State Duma

author Laws of the Russian Federation

Article 11

From the book Code of the Russian Federation on Administrative Offenses author Laws of the Russian Federation

Article 12. 25. Failure to comply with the requirement to provide a vehicle or stop a vehicle

author author unknown

Article 11.27. Driving a vehicle without a distinguishing sign on it and (or) trailers to it of the state of registration of the vehicle (trailer) and violation of other rules for the operation of the vehicle in the implementation of the international automobile

From the book Code of the Russian Federation on Administrative Offenses. Text with amendments and additions as of November 1, 2009 author author unknown

Article 12.25. Failure to comply with the requirement to provide a vehicle or to stop a vehicle 1. Failure to comply with the requirement to provide a vehicle to police officers or other persons who, in cases provided for

From the book of the Code of Administrative Offenses for motorists with comments. With changes for 2015 author Fedorova Ekaterina Nikolaevna

4.4. Vehicle inspection

From the book Hey Inspector, You're Wrong! All about how to resist the arbitrariness of the traffic police on the roads author Narinyani Alena

4.4. Inspection of a vehicle Inspection of a vehicle is an inspection of a vehicle carried out without violating its structural integrity. In order to inspect your car, the police officer must have grounds. Code of

2.2. Detention of a vehicle

author

2.2. Vehicle Detention What is a Vehicle Detention? This is the forced termination of the use of a vehicle, which includes its placement in a specialized parking lot. Specialized parking in turn -

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From the traffic police book. How to behave, what is important to know? author Shalimova Natalia Alexandrovna

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The stopping time of the car is determined by the following formula:

where is the reaction time of the driver, s;

– response time of the brake system, s;

– deceleration rise time, s;

k uh – braking efficiency coefficient;

V 0 – vehicle speed immediately before braking, m/s;

- the coefficient of adhesion of the wheels of the car with the road surface;

g- acceleration of gravity;

take equal to 0.8 s;

for vehicles with hydraulic brakes 0.2 - 0.3 s, for vehicles with pneumatic brakes 0.6 - 0.8 s;

calculated by the formula:

Where G- the weight of the car with a given load, N;

b- distance from the rear axle of the car to the center of gravity, m;

h c - distance from the center of gravity of the car to the road surface, m;

k 1 – rate of increase of braking forces, kN/s;

L- the base of the car, we accept 3.77 m.

The distance from the rear axle of the car to the center of gravity is calculated by the formula:

Where M 1 - the mass of the vehicle attributable to the front axle, kg;

M- the mass of the entire vehicle with a given load, kg;

k 1 selected depending on the type of brake system:

for vehicles with hydraulic brakes k 1 = 15 – 30 kN/s;

k uh is selected depending on the type of vehicle and its weight condition from the following table.

Table 4.1- Values of braking efficiency coefficients

Vehicle type	Braking efficiency factor k uh
Vehicle type	no load	with full load
Cars
Trucks weighing up to 10 tons and buses up to 7.5 m long
Trucks weighing more than 10 tons and buses longer than 10 m

When calculating, we accept:

a) the car before braking moves at a constant speed equal to 40 km/h ( V 0 = 11.11 m/s);

b) the coefficient of adhesion of the wheels of the car to the road surface = 0.6.

c) braking efficiency coefficient k uh we accept without load 1.2, with full load 1.5.

d) the rate of increase of braking forces k 1 =25kN/s.

For a GAZ-3309 car without load:

Using formula (4.3), we calculate the distance from the rear axle of the car to the center of gravity:

The deceleration rise time is calculated by the formula (4.2):

The stopping time of the car is determined by the formula (4.1):

4.2 Determination of the stopping distance of the vehicle with full load and without load

The determination of the stopping distance of the car is carried out according to the following formula:

(4.3)

For a GAZ-3309 car with a full load:

For a GAZ-3309 car without load:

4.3 Determining the deceleration of a vehicle with a full load on a slope and on an incline

When a vehicle brakes on a slope or uphill, its inertia force is balanced by the algebraic sum of the braking force and the uphill resistance force. When moving uphill, these forces are added, and on a slope they are subtracted.

Braking, the purpose of which is to stop as quickly as possible, is called emergency braking. During emergency braking, it is considered that the adhesion forces are fully used, that is, the braking forces reach their maximum value simultaneously on all wheels, the adhesion coefficients j x on all wheels are the same and unchanged over the entire braking period.

Under these assumptions, the deceleration process can be described by the dependence graph j c = f(t)(figure 3.1), called the braking diagram. The origin of coordinates corresponds to the moment of detection of danger. Dependence is applied to the diagram for better illustration V = f(t).

t r- the time elapsed from the moment the danger was detected to the start of braking is called the reaction time of the driver. Depending on the individual qualities, qualifications of the driver, the degree of his fatigue, traffic conditions, etc. t r can vary within 0.2 ... 1.5 s. When calculating, take the average value t r= 0.8 s.

t s- brake response time, s:

For hydraulic disc brakes t s= 0.05…0.07 s;

For hydraulic drum brakes t s= 0.15…0.20 s;

For pneumatic drum brakes t s= 0.2…0.4 s.

t n- deceleration rise time, s:

For cars t s= 0.05…0.07 s;

For trucks with hydraulic drive t n= 0.05…0.4 s;

For trucks with pneumatic drive t n= 0.15…1.5 s;

for buses t s= 0.2…1.3 s.

Maximum deceleration j h max when braking, it is reached when the maximum force on the brake pedal is reached, therefore it is assumed that the braking force will be unchanged, and deceleration can also be assumed to be constant.

During emergency braking on a level road, the maximum deceleration under adhesion conditions can be determined by the formula:

j s max \u003d j x ×g, m/s 2 . (3.1)

During t n(deceleration rise time) change in deceleration j s occurs proportionally to time, that is, the graph j s \u003d f (t n)- straight line.

t t– minimum braking time, s;

t p– release time (this is the time from the start of releasing the brake pedal to the occurrence of a gap between the friction elements).

The construction of the braking diagram is carried out in accordance with the selected time scales t, speed V and slowdowns j in a rectangular coordinate system, in accordance with Figure 3.1.

On the plots t r, t s speed V remains equal V o– speed at the beginning of braking; Location on t n the speed value gradually decreases, and in the section t t is depicted as a straight line, since the deceleration is constant ( V \u003d V o - j s ×t, m/s).