Mechanism of vehicle collision. Collision of vehicles Collision angle of vehicles cross traffic

To understand the scale of car damage after an accident, you need to clearly understand what happens directly at the moment of impact with the car body, which areas are subject to deformation. And you will be unpleasantly surprised to learn that during a frontal impact, the rear part of the body is skewed.

Accordingly, after unscrupulous body repair of the front end, even if the car was on the slipway, you will observe the trunk lid sticking, the sealing rubber rubbing, and much more. If you are interested in this topic, I suggest that you familiarize yourself with the educational material on collision theory, which was prepared by the specialists of our educational center.

General information

Theory collisions – This knowledge And understanding strength, emerging And existing at collision.

The body is designed to withstand the impacts of normal driving and to ensure the safety of passengers in the event of a vehicle collision. When designing the body, special care is taken to ensure that it deforms and absorbs the maximum amount of energy during a serious collision, while at the same time causing minimal impact on occupants. For this purpose, the front and rear parts of the body must be easily deformed to a certain extent, creating a structure that absorbs impact energy, and at the same time these parts of the body must be rigid in order to maintain a separation area for passengers.

Determination of violation of the position of body structural elements:

• Knowledge of collision theory: Understanding how a vehicle's structure reacts to the forces generated during a collision.
• Body inspection: search for signs indicating structural damage and its nature.
• Taking measurements: basic measurements used to identify violations of the position of structural elements.
• Conclusion: application of knowledge of collision theory in conjunction with the results of external inspection to assess the actual violation of the position of a structural element or elements.

Types of collisions

When two or more objects collide with each other, the following collision options are possible:

According to the initial relative position of objects

• Both objects are moving
• One is moving and the other is stationary
• Additional collisions

In the direction of impact

• Frontal collision
• Rear collision
• Side collision
• Rollover

Let's look at each of them

Both objects are moving:

One is moving and the other is stationary:

Additional encounters:

Front collision (frontal):

Rear collision:

Side collision:

Tipping:

Influence of inertial forces during a collision

Under the influence of inertial forces, a moving car tends to continue moving in a forward direction and when it hits another object or car it acts as a force.

A car standing still tends to maintain a stationary state and acts as a force opposing another car that hits it.

When colliding with another object, an "External Force" is created

As a result of inertia, “Internal forces” arise

Types of damage

Impact force and surface

Damage will vary for given vehicles of the same weight and speed depending on the object of the collision, such as a pole or wall. This can be expressed by the equation
f = F / A,
where f is the magnitude of the impact force per unit surface
F - force
A – impact surface
If the impact falls on a large surface, the damage will be minimal.
Conversely, the smaller the impact surface, the more severe the damage will be. In the example on the right, the bumper, hood, radiator, etc. are seriously deformed. The engine is moved rearward and the consequences of the collision reach the rear suspension.

Two types of damage

Primary damage

The collision between the vehicle and the obstacle is called the primary collision, and the damage it creates is called primary damage.
Direct damage
Damage caused by an obstacle (external force) is called direct damage.
Ripple Effect Damage
The damage created by the transfer of impact energy is called ripple effect damage.
Damage caused
Damage caused in other parts experiencing a tensile or pushing force due to direct damage or damage from the wave effect is called induced damage.

Secondary damage

When a car hits an obstacle, a large deceleration force is generated, which stops the car within a few tens or hundreds of milliseconds. At this point, passengers and objects inside the vehicle will attempt to continue moving at the vehicle's speed prior to the collision. A collision that is caused by inertia and that takes place inside the vehicle is called a secondary collision, and the resulting damage is called secondary (or inertial) damage.

Categories of violation of the position of parts of the structure

• Forward offset
• Indirect (indirect) displacement

Let's consider each of them separately

Forward offset

Indirect (indirect) displacement

Shock Absorption

The car consists of three sections: front, middle and rear. Each section, due to the nature of its design, reacts independently of the others in a collision. The car does not react to impact as one inseparable device. At each section (front, middle and rear), the influence of internal and (or) external forces manifests itself separately from other sections.

Places where the car is divided into sections

Crash-absorbing design

The main purpose of this design is to effectively absorb impact energy by the entire body frame in addition to the destructible front and rear parts of the body. In the event of a collision, this design ensures minimal deformation of the passenger compartment.

Front part of the body

Since the risk of collision is relatively high for the front end, in addition to the front side members, upper wing apron reinforcements and upper body side panels with stress concentration zones are provided to absorb impact energy.

Rear body

Due to the complex combination of rear quarter panels, rear floor box and spot welded elements, the impact absorption surfaces are relatively difficult to see in the rear, although the concept of impact absorption remains similar. Depending on the location of the fuel tank, the impact absorption surface of the rear floor side members is modified to absorb impact energy from collisions without damaging the fuel tank.

The ripple effect

Impact energy is characterized by the fact that it easily passes through strong areas of the body and finally reaches weaker areas, damaging them. This is the principle of the ripple effect.

Front part of the body

In a rear wheel drive vehicle (FR), if impact energy F is applied to the leading edge A of the front side member, it is absorbed through damage to zones A and B and also causes damage to zone C. The energy then passes through zone D and, after changing direction, reaches zone E. Damage, created in zone D is shown by the rearward displacement of the spar. The impact energy then causes ripple effect damage to the instrument panel and floor box before spreading over a larger area.

In a front-wheel drive vehicle (FF), the energy from a frontal impact will cause intense destruction of the front section (A) of the side member. The impact energy, causing the rear section B of the side member to bulge, eventually causes damage to the instrument panel (C) from the ripple effect. However, the ripple effect on the rear (C), reinforcement (lower rear spar) and steering gear bracket (lower instrument panel) remains negligible. This is because the central part of the side member will absorb most of the impact energy (B). Another characteristic of a front wheel drive (FF) vehicle is also damage to the engine mounts and surrounding areas.

If the impact energy is directed toward area A of the wing apron, the weaker areas B and C along the impact path will also be damaged, allowing some of the energy to be absorbed as it travels rearward. After zone D, the wave will impact the top of the post and the roof longitudinal beam, but the impact on the bottom of the post will be negligible. As a result, the A-pillar will tilt backwards, with the bottom of the A-pillar acting as a pivot point (where it connects to the panel). The typical result of this movement is a shift in the door landing area (the door becomes misaligned).

Rear body

Impact energy on the rear quarter panel causes damage at the contact area and then at the rear quarter panel. Also, the rear quarter panel will slide forward, eliminating any gap between the panel and the tailgate. If higher energy is applied, the rear door may be pushed forward, deforming the B-pillar, and damage may extend to the front door and A-pillar. Damage to the door will be concentrated in the folded areas at the front and rear of the exterior panel and in the door lock area of ​​the interior panel. If the rack is damaged, a typical symptom is a door that doesn't close properly.

Another possible direction of the wave effect is the path from the rear side pillar to the longitudinal beam of the roof.

In this case, the rear of the roof rail will be pushed up, creating a larger gap at the rear of the door. The junction between the roof panel and the rear side body is then deformed, causing the roof panel above the B-pillar to deform.

When studying the mechanism of a collision in the process of approaching a vehicle, the expert establishes either a violation of stability or loss of control before the collision and the reasons for such a violation, determines the speed of the vehicle before the incident and at the moment of the collision, establishes their location at certain times, the lane, the direction of movement, the angle of contact at collision.

By examining the process of vehicle interaction, the expert establishes their relative position at the moment of impact, determines the direction of the impact and its impact on the movement under study.

When studying the process of throwing a vehicle after a collision, the expert determines the location of the collision based on the remaining traces and the location of the vehicle after the incident, determines their speed of movement after the impact, and the direction of the throwing.

Establishing by an expert the mechanism of the collision and a technical assessment of the actions of the participants in the incident allow the investigative authorities and the court to resolve the issue of the cause of the incident and the circumstances that contributed to its occurrence.

The expert research methodology for establishing the collision mechanism depends on the type of collision. According to the main classification criteria that determine the collision mechanism, all vehicle collisions can be divided into the following groups:

According to the angle between the directions of movement of the vehicle - longitudinal (when driving parallel or close to parallel) and cross collisions. Longitudinal collisions are divided into oncoming and passing;

According to the nature of the interaction at the contact site during an impact - blocking (with complete damping of the relative speed at the moment of impact), sliding and tangential collisions.

These signs characterize the collision mechanism of both vehicles. In addition, the collision of each of the two colliding vehicles can be characterized by features unique to this vehicle:

By the nature of the movement immediately before the impact - a collision without reserve, with reserve to the right or left;

According to the place where the impact impulse is applied - a side collision is right - or left, front, rear, corner;

According to the direction of the impact impulse - the collision is central (when the direction of impact passes through the center of mass of the vehicle), right - or left eccentric.

This collision classification system makes it easy to formalize the characteristics of a collision.

§ 2. Mechanism of vehicle collision

General concept of the collision mechanism

The mechanism of a vehicle collision is a complex of circumstances related to objective laws that determine the process of vehicles approaching before a collision, and the interaction during the impact and subsequent movement until it stops; analysis of data on the circumstances of the incident allows the expert to establish the relationship between individual events, fill in the missing links and determine the technical cause incidents. A formal solution by an expert to questions based on individual scattered data, without a technical assessment of their compliance with each other and established objective data, without revealing and explaining the contradictions between them, can lead to incorrect conclusions.

When studying the mechanism of an incident, signs that directly allow one to establish one or another circumstance may be absent. In many cases, it can be established based on data about other circumstances of the incident, by conducting an expert study based on patterns that connect all the circumstances of the incident mechanism into a single set.

Features of impact in a collision

The theory of impact is based on ideal conditions, which greatly simplify the understanding of the interaction of bodies during impact. Thus, it is assumed that the contact of colliding bodies occurs at one point through which the interaction force passes, that the surfaces of the colliding bodies are absolutely smooth, there is no friction or engagement between them. Therefore, the impact force is perpendicular to the plane tangent to the surface of the colliding bodies at the point of their contact. The duration of the impact is assumed to be zero, and since the force impulse has a finite value, the impact force is considered to occur instantly, reaching an infinitely large value. The relative displacement of the colliding bodies during the impact is also considered to be zero, and therefore, the mutual repulsion of the colliding bodies occurs only under the influence of elastic deformation forces.

The interaction of a vehicle in a collision is much more complex than described above. During a vehicle collision, contact between them occurs over large areas, and various parts enter into it, causing interaction forces to appear in different places. The direction and magnitude of these forces depends on the design of the contacting parts (their shape, strength, rigidity, nature of deformation), therefore the interaction forces are different at different points of contact. Since the deformation of a vehicle during a collision can be very significant in depth, the interaction forces are variable in magnitude and direction.

The collision time is very short. There, no less than the relative displacement of the vehicle during this time can significantly affect their movement after the collision.

The direction of impact in a collision and the main direction of deformation of the contacting parts do not always coincide with the direction of the relative speed of the vehicle. They can coincide only in cases where the contacting areas do not slip during the impact. If slipping occurs over the entire surface, then transverse components of interaction forces arise, causing deformations in the direction of the least rigidity, and not in the direction of the longitudinal components, where the rigidity and strength of the deformed parts can be much higher (for example, when hitting at an angle on the side of the door the surface of the cabin is deformed not in the direction of the impact, but in the transverse direction if the impact was sliding).

It is also impossible to assume that the line of impact (the vector of the resultant impulses of the impact forces) during a collision passes through the point of initial contact. If the area of ​​the deformed area is large, the main blow can be delivered at a considerable distance from this point when interacting with stronger and more rigid parts than at the point of initial contact.

The vehicle collision mechanism can be divided into three stages: vehicle approach before the collision, interaction upon impact, and kickback (movement after the collision).

First stage of the collision mechanism– the process of rapprochement – ​​begins from the moment a danger to traffic arises, when in order to prevent an incident (or reduce the severity of the consequences) the drivers must immediately take the necessary measures, ends at the moment of initial contact of the vehicle. At this stage, the circumstances of the incident are determined to the greatest extent by the actions of its participants. At subsequent stages, events usually develop under the influence of irresistible forces arising in accordance with the laws of mechanics. Therefore, in order to resolve issues related to the assessment of the actions of the participants in the incident in terms of compliance with their traffic safety requirements, it is of particular importance to establish the circumstances of the incident at its first stage (the speed and direction of movement of the vehicle before the incident, their location along the width of the roadway).

Some circumstances of the incident at the first stage cannot be established directly on the spot or through questioning witnesses. Sometimes they can be established through expert examination of the collision mechanism at subsequent stages.

Second stage of the collision mechanism– interaction between vehicles – begins from the moment of initial contact and ends at the moment when the influence of one vehicle on another stops and they begin to move freely.

The interaction of a vehicle in a collision depends on the type of collision, determined by the nature of the impact, which can be blocking or sliding. During a blocking impact, the vehicles seem to stick together in separate sections, and there is no slipping between them. During a sliding impact, the contacting areas are displaced relative to each other, as the speed of the vehicles is equalized.

The process of a vehicle collision during a blocking impact can be divided into two phases.

In the first phase, deformation of the contacting parts occurs as a result of their interaction. It ends when the relative speed of the vehicle in the contact area drops to zero and lasts a fraction of a second. Enormous impact forces, reaching tens of tons, create large decelerations (accelerations). With eccentric impacts, angular accelerations also occur. This leads to different changes in the speed and direction of movement of the vehicles and their turn. But since the impact time is negligible, the vehicles do not have time to significantly change their position during this phase, therefore the general direction of the deformations usually almost coincides with the direction of the relative velocity.

In the second phase of the blocking impact, after the completion of mutual penetration of the contacting sections, the vehicles move relative to each other under the influence of elastic deformation forces, as well as mutual repulsion forces arising during an eccentric impact.

The magnitude of the impulse of elastic deformation forces compared to the impulse of impact forces is large. Therefore, with a slight eccentricity of the impact and deep penetration of the contacting parts, the adhesion forces between them may prevent the separation of the vehicle and the second phase of the impact may end before their separation.

A sliding collision occurs in cases where the velocities in the contact areas are not equalized and before the vehicles begin to move away from each other, the interaction occurs sequentially between their different parts located along the line of relative displacement of the contacting areas. In the event of a glancing impact, the vehicle manages to change its relative position during the collision, which somewhat changes the direction of the deformations.

During contact, transverse velocities of the vehicles arise, which leads to a deviation in the direction of their deformations.

A sliding impact with a small depth of mutual penetration and a high speed of relative displacement is called a tangential impact. With such an impact, the vehicle speeds after the collision change slightly, but the direction of their movement will change significantly.

An expert examination of traces and damage on the TC allows us to establish the circumstances that determine the second stage of the collision mechanism - the process of interaction during contact.

The main tasks that can be solved during an expert examination of marks and damage on a vehicle are:

1) establishing the angle of relative position of TC at the moment of collision;

2) determination of the point of initial contact on the vehicle.

The solution to these two problems reveals the relative position of the TC at the moment of impact, which makes it possible to establish or clarify their location on the road, taking into account the signs remaining at the scene of the incident, as well as the direction of the collision line;

3) establishing the direction of the collision line (the direction of the shock impulse is the direction of the relative speed of approach). Solving this problem makes it possible to find out the nature and direction of TC movement after an impact, the direction of the traumatic forces acting on passengers, the angle of collision, etc.;

4) determination of the collision angle (the angle between the directions of movement TC before the impact). The collision angle allows you to determine the direction of movement of one vehicle, if the direction of the other is known, and the amount of movement of the TC in a given direction, which is necessary when identifying the speed of movement and displacement from the collision site.

In addition, problems may arise related to establishing the causes and time of occurrence of damage to individual parts. Such problems are solved, as a rule, after removing damaged parts from the TC through a comprehensive study using automotive, traceological and metallurgical methods.

Determining the angle of relative position of TC Oo from deformations and marks on the TC with sufficient accuracy is possible during blocking impacts, when the relative speed of approach of the TC at the points of their contact drops to zero, i.e., when almost all the kinetic energy corresponding to the speed of approach is spent on deformations .

It is assumed that during the short time of formation of deformations and damping of the relative speed of approach, the longitudinal axes TC do not have time to noticeably change their direction. Therefore, when the contacting surfaces of paired sections deformed during a collision are aligned, the longitudinal axes TC will be located at the same angle as at the moment of initial contact.

Consequently, to establish the angle ao, it is necessary to find paired areas on both vehicles that were in contact during a collision (dents on one vehicle corresponding to specific protrusions on the other, imprints of characteristic parts). It should be borne in mind that the selected areas must be strictly connected to the vehicle.

The location of areas on parts of the vehicle that are displaced or torn off during movement after an impact does not allow determining the angle ao if it is impossible to determine with sufficient accuracy their position on the vehicle at the moment of completion of the deformation upon impact.

The angle of relative position ao is found in several ways.

Determination of the angle ao with direct comparison of vehicle damage. Having installed two pairs of contacting areas on the TC, located as far as possible from each other, place the TC so that the distances between the contacting areas in both places are the same (Fig. 1.4).

Rice. 1.4. Scheme for determining the angle of relative position TC in a collision based on two pairs of contacted sections

By directly comparing TC, it is easier and more accurate to determine the points in contact. However, the difficulty of delivering both vehicles to one place when they are not transportable, and the difficulty of placing them relative to each other, in some cases may make the use of this method inappropriate.

The method for measuring the angle O 0 depends on the nature of the deformations of the vehicle body. It can be measured between the sides of the vehicle, if they are not damaged and parallel to the longitudinal axes, between the axes of the rear wheels, between specially laid lines corresponding to undeformed parts of the vehicle body.

Determination of the angle ao from the angles of deviation of the trace-forming object and its imprint.

Often, after a collision, clear imprints of parts of the other remain on one of the TCs - headlight rims, bumpers, sections of the radiator lining, the leading edges of the hoods, etc.

Having measured the angles of deviation of the plane of the trace-forming object on one TC and the plane of its imprint on the other (angles Xi and x?) from the direction of the longitudinal axes of the TC, we determine the angle using the formula

where is the relative position angle measured from the direction of the longitudinal axis of the first vehicle.

The direction of counting angles in calculations is taken counterclockwise.

Determination of the angle ao by the location of two pairs of contacting areas. In those

In cases where there are no prints on the deformed parts of the TC that would allow measuring the angles of deviation of the contact plane from the longitudinal axis, it is necessary to find at least two pairs of contacted areas located as far as possible from each other.

Having measured the angles of deviation from the longitudinal axes of the straight lines connecting these sections to each other on each TCl, we determine the angle ao using the same formula as in the previous one

case.

When the impact during a collision is sharply eccentric in nature, after the impact the TC rotates through a significant angle, and the depth of mutual penetration is large, the TC manages to rotate through a certain angle Da during the deformation, which can be taken into account if high accuracy in determining the angle ao is required.

The approximate value of the correction Da can be determined by the following calculation:

This formula is approximate; it is derived from the conditions of a uniform reduction to zero of the relative speed of approach of the centers of gravity TC during a collision and a uniform reduction to zero of the angular velocity TC at the moment of stopping. However, these assumptions cannot give a significant error when calculating the value of the angle a 0.

Please note that during an eccentric collision, the TCs may rotate in different directions. In this case, the angles Yes must be determined for both TCs and the correction is equal to the sum of these angles.

When turning TCs of the same type (having similar masses) in one direction, the correction is a difference in angles and is very insignificant, so the calculation is impractical.

When a vehicle with a larger mass collides with a lighter one, the angle Yes is determined only for the lighter vehicle.

The relative speed (meeting speed V 0) is most easily determined graphically by constructing a triangle along two sides and the angle between them (see Fig. 1.3). You can also determine it using calculations:

Example. As a result of the impact, the left headlight of car No. 1 was turned to the left at an angle to the longitudinal axis. The imprint of the headlight on the radiator lining of car No. 2 is turned to the right at an angle

Vehicle speeds before collision

Mutual penetration of cars in the direction of impact of 0.8 m.

After the impact, car No. 1 shifted without turning, car No. 2 turned at an angle її 2 = 180°, moving towards the stopping place nAdhesion coefficient

Vehicle collision.

CLASSIFICATION OF COLLISION TYPES

I. In the direction of movement of the vehicle.

1. Longitudinal - collision without relative displacement of the vehicle in the transverse direction, ᴛ.ᴇ. when moving in parallel courses (angle α is equal to 0 or 180 degrees).

2. Cross - collision when a vehicle moves on non-parallel courses, ᴛ.ᴇ. when one of them shifted transversely towards the lane of the other (the angle is not equal to 0 or 180 degrees).

II. According to the nature of mutual rapprochement of the vehicle.

The sign of an accident is determined by the magnitude of the collision angle.

Based on this criterion, collisions are divided into:

1. Counter - a collision in which the projection of the speed vector of one vehicle onto the speed direction of another is opposite to this direction; The vehicles approached each other with a deviation towards each other (angle α > 90;< 270 градусов).

2. Along the way - a collision in which the projection of the velocity vector of one vehicle onto the velocity direction of another coincides with this direction; The vehicles approached each other, moving with deviation in one direction (angle α< 90; >270 degrees).

3. Transverse - a collision in which the projection of the velocity vector of one vehicle onto the velocity direction of the other is O (angle α is 90; 270 degrees).

III. According to the relative location of the longitudinal axes of the vehicle.

The sign is determined by the angle of mutual arrangement of their longitudinal axes.

1. Direct - a collision when the longitudinal or transverse axis of one vehicle and the longitudinal axis of the second vehicle are parallel (angle α is 0; 90 degrees).

2. Oblique - a collision in which the longitudinal axes of the vehicle were located at an acute angle relative to each other;

(angle α is not equal to 0; 90 degrees).

IV. Based on the nature of vehicle interaction upon impact.

The sign is determined by deformations and marks on the contact areas.

Based on this criterion, collisions are divided into:

1. Blocking- a collision in which, during contact, the relative speed of the vehicle in the contact area by the time the deformations are completed decreases to 0.

2. Sliding - a collision in which, during contact, slippage occurs between the contacted areas due to the fact that until the moment the vehicle leaves contact with each other, their speeds are not equalized.

3. Tangent - a collision in which, due to the small amount of overlap of the contacting parts of the vehicle, they receive only minor damage and continue to move in the same directions (with a slight deviation and reduction in speed). In such a collision, horizontal traces (scratches, rubbing marks) remain in the contact areas.

V. In the direction of impact relative to the center of gravity.

The sign is determined by the direction of the vector of the resultant of the shock pulse vectors.

Based on this criterion, collisions are divided into:

1. Central - when the direction of the collision line passes through the center of gravity of the vehicle.

2. Eccentric - when the line of collision passes at some distance from the center of gravity, to the right (right excentric) or to the left (left eccentric) of it .

VI. At the location of the strike.

Based on this criterion, collisions are divided into:

1. Front (frontal) - a collision in which traces of direct contact upon impact with another vehicle are located on the front parts.

2. Front corner right and front corner left - collision , in which traces of contact are located on the rear and adjacent side parts of the vehicle.

3. Side right and side left - a collision in which the impact was delivered to the side of the vehicle.

4. Rear corner right and rear corner left - a collision in which traces of direct contact are located on the rear and adjacent side parts of the vehicle.

5. Rear - a collision in which the contact marks caused by the impact are located on the rear parts of the vehicle.

Collision site. To reconstruct the mechanism of an accident associated with a collision of cars, it is necessary to determine the location of the collision, the relative position of the cars at the moment of impact and their location on the road, as well as the speed of the cars before the impact. The initial data presented to the expert in such cases is usually incomplete, and there is no sound methodology for determining the necessary parameters. Therefore, when analyzing collisions, it is usually impossible to give an exhaustive answer to all the questions that arise. The most accurate results are obtained by the joint work of experts from two specialties: a criminologist (traces examiner) and an automotive technician. However, the experience of such work is still limited and an expert automotive technician often has to perform the functions of a trace examiner.

The location of the vehicle collision on the roadway is sometimes determined based on the testimony of participants and eyewitnesses of the accident. However, witness testimony is usually inaccurate, which is explained by the following reasons: the stressful state of the participants in the accident; short duration of the collision process; the absence of stationary objects in the accident area that drivers and passengers can use to record the location of the collision in their memory; involuntary or deliberate distortion of the circumstances of the case by witnesses.

In addition, there may be no witnesses to the accident.

Therefore, to determine the location of the collision, it is necessary to examine all objective data resulting from the incident. Such data that allows an expert to determine the location of the collision on the roadway may be:

information about the traces left by vehicles in the collision zone (traces of rolling, longitudinal and transverse sliding of tires on the road, scratches and potholes on the surface from vehicle parts);

data on the location of spilled liquids (water, oil, antifreeze, antifreeze), accumulations of glass and plastic fragments, dust particles, dirt that fell from the lower parts of vehicles during a collision;

information about traces left on the roadway by objects thrown as a result of an impact (including the body of a pedestrian), fallen cargo or parts separated from vehicles;

characteristics of damage received by vehicles during a collision;

location of vehicles on the roadway after an accident.

Rice. 7.9. Tire tracks on the road:

a-sliding trace (skidding), b-rolling trace, c-transverse sliding trace, d-change of traces during a transverse collision, d- same for oncoming collision

A detailed study of traces belongs to the subject of transport traceology. Only general concepts are given here.

Of the listed initial data, the most information for an expert is provided by tire tracks on the road. They characterize the actual position of vehicles on the roadway and their movement during an accident. In the period between the collision and the inspection of the accident scene, such traces usually change slightly. The remaining signs characterize the position of the collision site only approximately, and some of them can even change in a relatively short period of time, sometimes significantly. For example, water flowing from a damaged radiator on a hot summer day often dries up before the traffic inspector arrives at the scene of the accident. The most typical examples of tire tracks are shown in Fig. 7.9, a-c.

The location of the collision and the position of the vehicles at the moment of impact can sometimes be determined by changes in the nature of the tire tracks. Thus, in the event of an eccentric oncoming and transverse collision, the tire tracks at the collision site are displaced transversely in the direction of vehicle movement (Fig. 7.9, d).

In the event of an oncoming collision, the skid marks may be interrupted or become less noticeable. If the shock loads acting on the braked wheel are directed from top to bottom, then it may become unblocked for a moment, since the adhesion force will exceed the braking force (Fig. 7.9, d).

R
is. 7.10. Longitudinal section of the furrow on the coating:

A - asphalt concrete, b - cement-concrete

If the impact load is directed from bottom to top, the wheel may come off the road. Sometimes, on the contrary, at the moment of impact, the wheel becomes jammed by deformed parts of the car and, having stopped rotating, leaves a tire mark on the road, usually small.

Parts of the car body, chassis and transmission that are destroyed by impact can leave marks on the surface in the form of potholes, grooves or scratches. The beginning of these tracks is usually located near the collision site. The same traces are left by parts (pegs, pedals, handlebars) of an overturned motorcycle, scooter and bicycle when dragged or thrown during an accident. Scratches and grooves on the coating begin with a barely noticeable mark, then its depth increases. Having reached maximum depth, the trail ends abruptly (Fig. 7.10). On an asphalt concrete pavement, a bump forms at the end of a dent due to plastic deformation of the mass.

In some cases, particles of its mass remain on a car part that has damaged the coating. Identification of these particles allows us to clarify the part that came into contact with the coating.

The trajectories of objects thrown away during the collision can give some idea of ​​the location of the collision. These trajectories may vary depending on the shape and mass of objects, as well as the nature of the road. Objects that are round or similar in shape (wheels, hubcaps, headlight rims), rolling, can move a long distance from the place of fall. A pothole or elevation on the surface creates local increased resistance to the movement of an object, promoting its unfolding and curvature of its trajectory. However, the initial sections of the trajectories are usually close to rectilinear, and if there are several tracks located at an angle, we can assume that the collision site is located near the point of their intersection.

After a vehicle collision on the road

Dry particles of crumbled earth, dried mud, and dust almost always remain in the accident zone. The location of these particles coincides quite accurately with the location of the part on which the ground was located during the collision. The earth can crumble simultaneously from several parts, including those far removed from the place of initial contact of the vehicles. For example, in the event of an oncoming collision between vehicles, dirt particles may fall off the rear bumper or from the rear axle housings. Therefore, when determining the location of the collision, the expert needs to find out from which vehicle and from which part the earth was released. The answer to this question, obtained through forensic analysis, will help to more accurately determine the relative position of the vehicles and their location on the road at the time of impact.

Very often, when a car collides, glass and plastic parts break, the fragments of which fly in different directions. Some of the fragments fall on car body parts (hood, fenders, running boards) and bounce off them or move with them, after which they fall onto the road. Glass particles that are in direct contact with parts of an oncoming car fall near the collision site, since their absolute speed is low. Particles that did not come into contact continue to move by inertia in the same direction and fall further to the ground. In addition, small pieces of glass and plastic may be dislodged by wind, rain, vehicles or pedestrians between the incident and the start of the inspection. As a result, the fragment dispersion zone turns out to be quite extensive (sometimes its area is several square meters) and it is impossible to determine the exact position of the impact site from it.

As a rule, many signs remain in the accident zone, each of which characterizes the location of the collision in its own way. However, none of these signs, taken separately, can serve as a basis for a final conclusion. Only a comprehensive study of the entire body of information allows an expert to solve the tasks assigned to him with the required accuracy.

P
car position at the moment blow. All variety of vehicle collisions depending on angle st between their velocity vectors can be divided into several types. At st 180° collision is called counter(Fig. 7.11, / and //), and when st 0, when cars move in parallel or close to them courses, - incidental(Fig. 7.11, /// and IV). At st 90° collision is called cross(Fig. 7.11,V), and at 0<st<90° (рис. 7.11,VI) and at 90°<ct<180° (рис. 7.11,VII) - oblique.

Figure 7. 11. Types of collisions

If the load acts on the end surfaces of cars (see Fig. 7.11, / and ///), then the impact is called straight; if it falls on the sides, - sliding(see Fig. 7.11, // and IV).

Figure 7. 12. Angle determination st

The position of vehicles at the moment of impact is often determined through an investigative experiment based on the deformations resulting from the collision. To do this, the damaged cars are placed as close to each other as possible, trying to align the areas that were in contact upon impact (Fig. 7.12, a). If this cannot be done, then the cars are positioned so that the boundaries of the deformed areas are located at equal distances from each other (Fig. 7.12, b). Since such an experiment is quite difficult to carry out, sometimes cars are drawn on a diagram scale and, having marked the damaged zones on them, the collision angle is determined graphically.

These methods give good results in the examination of oncoming cross collisions, when the contacting areas of the vehicles do not have relative movement during the impact. In oblique and angular collisions, despite the short duration of the impact, the cars move relative to each other. This leads to slipping of the contacting parts and their additional deformations. As an example in Fig. 7.13, a shows an eccentric collision between a car and a truck. As a result of the impact, a Rud force arises at the point of initial contact, which, together with the inertial force, produces a moment tending to turn the passenger car in the direction of movement clockwise. The car, rotating, sequentially takes positions I... IV, which leads to the emergence of a large deformation zone for both vehicles (the truck is conventionally considered stationary). If we define the angle Using the methods described above (Fig. 7-13, b), one can come to the incorrect conclusion that the cars at the initial moment of impact were located at an angle of about 35°.

Rice. 7.13. Eccentric vehicle collision:

A - collision process;

b - incorrect angle definition st,

Figure 7.14. Damage to vehicle surfaces during collisions

A - scratches when the primer peels off, b - burrs on the scratch

Sometimes the angle st is determined from photographs of damaged vehicles. This method gives good results only when pictures of different sides of the car are taken at right angles from the same distance.

An idea of ​​the relationship between the speeds of impacting vehicles and the direction of their movement can be obtained by examining damage to painted surfaces and metal parts. Marks on the surface of a damaged car that are wider than deep and longer than wide are called scratches. Scratches run parallel to the damaged surface. They have small depth and width at the beginning, widening and deepening towards the end. If the primer is damaged along with the paintwork, it peels off in the form of wide drop-shaped scratches 2-4 long. mm. The wide end of the drop is directed in the direction of movement of the object that caused the scratch. At the end of the drop, the primer may peel off, forming transverse cracks about 1 mm(Fig. 7.14, A). Damages whose depth is greater than their width are called nicks and dents. The depth of the scratch usually increases from its beginning to its end, which makes it possible to determine the direction of movement of the scratched object. Sharp burrs often remain on the surface of the scuff (Fig. 7.14, b), which are bent in the same direction in which the scratched object moved.

Knowing the direction of movement of the object that caused the scratch or scuff (shown by an arrow in Fig. 7.14), the expert determines which of the cars was moving at a higher speed during a passing glancing impact. The car that was moving slower had scratch marks directed from the rear to the front, while the car that was overtaking had scratch marks in the opposite direction.

Important information about the mechanism of an accident can be obtained by studying the position of cars after an impact. In the event of a direct oncoming collision, the speeds of the vehicles cancel each other out. If their mass and speed were approximately the same, then they stop near the collision site. If the masses and speeds were different, then the car moving at a lower speed or the lighter one is thrown back. Sometimes a truck driver does not take his foot off the throttle pedal before a collision and, confused, continues to press it. In this case, a truck can drag an oncoming passenger car a fairly long distance from the collision site.

Sliding collisions are accompanied by a small loss of kinetic energy with relatively significant destruction and deformation of the body. If drivers did not brake before a collision, they may drive far away from the collision site.

At the moment of impact of the cars, the speed u 1 and U 2 . the contacting parts add up and the colliding sections move for some time in the direction of the resulting velocity U 3 (Fig. 7.15). The centers of gravity of cars also move in the same direction. Although after the impact loads cease, the cars move under the influence of external forces and in the future the trajectories of both cars may change, but the general direction of movement of the centers of gravity allows us to determine the position of the cars at the time of the collision.

Determining vehicle speed before impact Determining the initial speed of a car based on the data contained in the materials of a criminal case is usually quite difficult, and sometimes impossible. The reasons for this are the lack of a universal calculation method suitable for all types of collisions and the lack of initial data. Attempts to use the recovery factor in these cases are not

Rice. 7.16. Schemes of a car colliding with a standing car:

a - both the vehicle is not braked;

b - both cars are braked;

c - the front car is braked;

d - the rear car is braked

lead to positive results, since reliable values ​​of this coefficient in a collision have not been published. The experimental value should not be used in vehicle collision studies. TO beat , valid for a vehicle hitting a hard obstacle. The processes of deformation of parts in both cases are fundamentally different; accordingly, the recovery coefficients should also be different; this is evidenced, for example, in Fig. 7.6. The possibility of accumulating sufficient experimental information, given the variety of car models, their speeds and types of collisions, is vanishingly small. In Japan, researchers Takeda, Sato and others proposed an empirical formula for the recovery coefficient

Where U * a - vehicle speed, km/h.

However, the experimental points on the graph that served as the basis for this formula are located with a large scatter relative to the approximating curve, and the calculated values ​​of Ksp may differ from the actual ones by several times. Therefore, the formula can be recommended only for purely approximate calculations, and not for use in expert practice, especially since it describes accidents with foreign cars.

The lack of reliable information on the coefficient of restitution often forces experts to consider the limiting case, considering the impact to be completely inelastic (TO beat =0).

It is possible to determine the parameters of a direct collision (see Fig. 7.11, / and ///) only if one of the cars was stationary before the impact, and its speed U 2 = 0. After the impact, both cars move as one unit with speed U" 1 (Fig. 7.16).

In this case, various options are possible.

I. Both cars are not braked, and after the impact they roll freely (Fig. 7.16, a) with an initial speed U" 1 .

The equation for kinetic energy in this case

where S pn is the movement of cars after the impact; dv - coefficient of total resistance to movement, determined by formula (3.7a).

Therefore, U" 1 =
. In addition, according to formula (7.2) when U 2 =0 andU" 1 =U" 2 speed of car 1 before impact

II. Both cars are braked, after the impact they move together at a distance S pn (Fig. 7.16, b) with initial speed U" 1 .

Speed ​​of cars after impact U" 1 =
.

Vehicle speed 1 at the moment of impact - formula (7.15).

Speed ​​of car 7 at the beginning of the braking distance

where S yu1 is the length of the skid mark of car 1 before the impact.

Vehicle 1 speed before braking

III. A stationary car is braked 2, car 1 is not braked (Fig. 7.16, c).

After the impact, both cars move the same distance S pn with the initial speed U" 1 . The kinetic energy equation in this case is: (T 1 +t 2 )*(U" 1 ) 2 /2=(m 1dv + m 2 x ) gS Mon , where

IV.Standing car 2 not inhibited. Before the impact, the rear car 1, in a braked state, moved a distance S yu1. After the impact, the displacement of car 1 is S Mon1 , and moving the car 2 - S pn2.

Similar to previous cases

The speeds U 1 , U a 1 and U a are determined respectively according to formulas (7.15)-(7.17).

It is possible to apply this technique to analyze an oncoming or passing collision in which both cars were moving only if the investigation or court established the speed of one of the cars.

In case of a cross collision (Fig. 7.17, A) both cars usually make a complex motion, as this causes each car to spin around its center of gravity. The center of gravity, in turn, moves at a certain angle to the original direction of movement. Let car drivers 1 and 2 they braked before the collision, and the diagram shows brake marks S 1 And S2.

Figure 7.17. Car collision patterns

A - cross,

b - oblique

After the collision, the center of gravity of car 1 moved a distance S" 1 at an angle Ф 1, and the center of gravity of the car 2 - to a distance S" 1 at an angle Ф 2.

The entire amount of motion of the system can be decomposed into two components in accordance with the initial direction of movement of cars 1 and 2. Since the amount of motion in each of the indicated directions will not change, then

(
7.18.)

where U" 1 and U" 2 - speed of cars 1 and 2 after the blow

These speeds can be found. Assuming that the kinetic energy of each car after an impact turns into the work of friction of tires on the road during translational movement at a distance S pn1 (S pn2) and rotation around the center of gravity at an angle 1 ( 2)

Work of tire friction on the road during forward motion of a car 1

The same when turning it relative to the center of gravity at an angle 1

Where A 1 And b 1 - distances from the front and rear axles of vehicle 1 to its center of gravity, R z 1 and R z 2 - normal road reactions acting on the front and rear axles of vehicle 1, 1 - vehicle rotation angle 1, rad

Where L" - base car 1 Therefore,

Hence the speed of the car 1 after the collision

In the same way we find the speed of car 2 after the collision

Where L" And 2 - base and angle of rotation of the car, respectively 2; A 2 and b 2 - distances from the front and rear axles of the car 2 to its center of gravity.

Substituting these values ​​into formula (7.18), we determine the speed of car 1

Same for car 2

Knowing the speeds U 1 and U 2 of the cars immediately before the collision, you can use expressions (7.16) and (7.17) to find the speeds at the beginning of the braking distance and before braking.

When making calculations, it should be borne in mind that the distances (S pn1 and S pn2) and angles (Ф 1 and Ф 2) characterize the movements of the centers of gravity of the cars. The distances S pn1 and S pn2 can differ significantly from the length of the tire tracks on the surface. Angles Ф 1 and F 2 may also differ from the angles of the tracks left by the tires. Therefore, both distances and angles are best determined using a diagram drawn to scale, marking the position of the center of gravity of each vehicle involved in an accident.

In practice, there are often accidents in which cars collide at an angle st , different from straight. The sequence of calculation of such collisions does not differ from that described above. Only the amount of motion of the system needs to be designed into components corresponding to the initial directions of movement of cars 1 and 2, which will entail complication of formulas (7.18) and (7.19).

Then, according to Fig. 7.17, b:

Speeds U" 1 and U" 2 in equations (7.22) and (7.23) are determined by formulas (7.20) and (7.21). The direction of counting the angles (Ф 1 and Ф 2 is shown in Fig. 7.17. Denoting the right-hand sides of equations (7.22) and (7.23) respectively through A 1 and B 1, you can find the speeds of the cars before the impact:

The speeds of cars before a cross collision, determined in the described way, are the minimum possible, since the calculations do not take into account the energy expended on the rotation of both cars. Actual speeds may be 10-20% higher than estimated.

Sometimes the so-called “reduced” speed of the car is used, i.e. the speed at which the car, having hit a stationary obstacle, receives the same damage and deformation as in a collision. Naturally, there are no fundamental objections to such a parameter, but there are no reliable ways to determine it.

Technical ability to prevent a collision. The answer to the question of the possibility of preventing a collision is related to determining the distance between cars at the time a dangerous road situation arises. Establishing this distance by expert means is difficult and often impossible. The information contained in investigative documents is usually incomplete or contradictory. The most accurate data is obtained through an investigative experiment involving visiting the scene of an accident.

Let us first consider a passing collision.

If the collision was the result of unexpected braking of the front car, then with a working brake system of the rear car there can only be two reasons: either the driver of the rear car was late, or he chose the wrong distance. If the distance is correctly chosen and the rear vehicle brakes in a timely manner, a collision is obviously avoided.

If the actual distance between cars S f is known, then it is compared with the distance S b , minimum required to prevent a collision. If the brake light of the leading car is operational and turns on when the driver presses the brake pedal, then the minimum distance under safety conditions is S b = U"" a (t"" 1 + t"" 2 + 0.5t"" 3) +(u"" a) 2 /(2j"")- U" a (t" 2 + 0.5t" 3) - (U" a ) 2 /(2 j"), where one stroke indicates the parameters of the front car, and two - the rear.

If both cars are moving at the same speed AND U" a =U"" a =U a , THAT S b = U a+U 2 a(1/j""-1/j")/2.

The greatest safe distance should be when a truck follows a passenger car, since in this case t"" 2 > t" 2 ; t"" 3 > t" 3 And j" If the vehicles are of the same type, then when U" a = U"" a = U a distance S b = U a t"" 1 .

When S f S b we can conclude that the driver of the rear car had the technical ability to avoid a collision, and if S F < S b - the conclusion is that he did not have such an opportunity.

For some cars, the moment the brake light comes on does not coincide with the start of pressing the brake pedal. The delay can be 0.5-1.2 s and be one of the causes of an accident.

Drivers moving in the same lane can only prevent an oncoming collision if both have time to brake and stop the cars. If at least one of the cars does not stop, an accident will be inevitable.

Let's consider the possibility of preventing an oncoming collision. Figure 7.18 shows in “path-time” coordinates the process of approaching two cars 1 and 2. The following positions are marked with Roman numerals

/ -at the moment when drivers could assess the current road situation as dangerous and had to take the necessary measures to eliminate it,

// -at the moments when each of the drivers actually began to react to the danger that had arisen,

/// -at the moments corresponding to the beginning of the formation of tracks, skidding on the surface (the beginning of full braking),

IV- at the moment of a car collision.

In numbers V The positions of the cars are marked in which they would have stopped if they had not collided, but continued to move in a braked state (presumptive version).

Figure 7.18. Diagram of vehicle movement during an oncoming collision

The distance between cars at the time of a dangerous situation is 5v. Section //-/// corresponds to the movement of cars at constant speeds over a total time T 1 (T 2 ). The distances S a 1 and S a 2 that separated the cars from the collision site at the initial moment must be determined investigatively, as well as their initial velocities U a 1 and U a 2 .

An obvious condition for the possibility of preventing a collision: the visibility distance must be no less than the sum of the stopping distances of both vehicles:

S in =S a1 + S a2 So 1 + So 2, where indices 1 and 2 refer to the corresponding cars. To implement this condition, drivers must simultaneously react to the emerging traffic hazard and immediately begin emergency braking. However, as expert practice shows, this rarely happens. Typically, drivers continue to approach each other for some time without slowing down, and brake significantly late when a collision cannot be prevented. Such accidents are especially frequent at night, when one of the drivers drives onto the left side of the road, and insufficient lighting makes it difficult to determine distances and recognize vehicles.

To establish a causal relationship between the actions of drivers and the resulting consequences, it is necessary to answer the question: did each driver have the technical ability to prevent a collision, despite the wrong actions of the other driver? In other words, would a collision have occurred if one driver had reacted to the danger in a timely manner and braked earlier than he actually did, and the other driver acted in the same way as during the accident. To answer this question, the position at the moment of stopping one of the cars, for example the first one, is determined, provided that its driver would react in a timely manner to a dangerous situation. After this, the position of the second car at the moment of stopping is found if it had not been detained during the collision.

Condition for the ability to prevent a collision for the driver of car 1

for car driver 2

where S pn1 and S pn2 are the distances that the cars would have moved from the collision site to the stop if they had not been detained.

The approximate sequence of calculations when assessing the actions of the driver of car 1 is as follows.

1. The speed of the second car at the moment of full braking

Where t"" 3 - vehicle deceleration rise time 2; j" - steady deceleration of the same vehicle.

2. Full braking distance of the second car S" 4 = U 2 u2 /(2 j"").

3. The distance that the second car would have moved to a stop from the collision site if the collision had not occurred,

where S yu2 is the length of the skid mark left on the surface by the second car before the collision site.

4. Stopping distance of the first car So 1 = T"U a1 .+U 2 a1/(2j").

5. Condition for the driver of the first car to prevent a collision, despite the untimely braking of the second driver: S a 1 So 1 +S pn2.

If this condition is met, then the driver of the first car had the technical ability, with a timely response to the appearance of an oncoming car, to stop at a distance that excluded a collision.

In the same sequence, it is determined whether the driver of the second car had such an opportunity.

Example. On a road 4.5 m wide, a collision occurred between two vehicles: a ZIL-130-76 truck and a GAZ-3102 Volga passenger car. As established by the investigation, the speed of the ZIL-130-76 car was approximately 15 m/s, and the speed of the GAZ-3102 car was 25 m/s.

During the inspection of the accident scene, brake marks were recorded. The rear tires of a truck left a skid mark 16 m long, and the rear tires of a passenger car left a skid mark 22 m long. As a result of an investigative experiment with a visit to the scene of an accident, it was established that at the moment when each of the drivers had the technical ability to detect an oncoming car and assess the road situation as dangerous, the distance between the cars was about 200 m. At the same time, the ZIL-130-76 car was located at a distance of about 80 m from the collision site, and the GAZ-3102 Volga car was at a distance of about 120 m.

Data required for calculation:

car ZIL-130-76 T"=1.4 s; t" 3 =0.4 s; j"=4.0 m/s 2;

car GAZ-3102 "Volga" T"=1.0 s; t"" 3 =0,2 With; j""=5.0 m/s 2.

Determine whether each driver has the technical ability to prevent a car collision.

Solution.

1. Stopping tracks for the ZIL-130-76 car So 1 =15*l, 4+ 225/(2*4.0) =49.5 m; car GAZ-3102 "Volga" 5„2=25*1.2+ 625/(2*5.0) =92.5 m.

2. Condition for being able to prevent a collision: So 1 + So 2 = 49.5 + 92.5 = 142.0 m; 142.0

The sum of the stopping distances of both cars is less than the distances separating them from the place of the upcoming collision. Consequently, if both drivers had correctly assessed the current traffic situation and made the right decision at the same time, the collision could have been avoided. After the cars stopped, there would be a distance of about 58 m between them: S= (80+ 120)- (49.5+ 92.5) =58 m.

Let's determine which driver had the technical ability to prevent the collision, despite the wrong actions of the other driver. First, possible actions of the ZIL-130-76 driver.

3. The speed of the GAZ-3102 “Volga” car at the moment of the start of full braking is U ω2 = 25-0.5 *0.2* 5.0 =24.5 m/s.

4. Full braking distance of the GAZ-3102 Volga car S"" 4 = 24.5 2 /(2*5.0) =60.0 m.

5. Movement of the GAZ-3102 Volga car from the collision site in a braked state in the absence of a collision S pn2 = 60.0 -22.0 ==38.0 m.

6. Condition for the ZIL-130-76 driver to prevent a collision: So 1 + S pn2 =49.5+38.0=87.5> S a 1 =80 m.

The driver of the ZIL-130-76 car, even with a timely response to the appearance of the GAZ-3102 Volga car, did not have the technical ability to prevent a collision.

7. We carry out similar calculations in relation to the driver of the GAZ-3102 Volga car:

As calculations showed, the driver of the GAZ-3102 Volga had a real technical ability to prevent a collision, despite the fact that the driver of the ZIL-130-76 was late with the start of emergency braking

Thus, although both drivers did not react in a timely manner to the appearance of danger and both braked with some delay, only one of them in the current situation had the opportunity to prevent a collision, and the second did not have such an opportunity. To explain the obtained conclusion, we determine the movement of each car during the time spent by its driver.

Moving the ZIL-130-76 car

Moving the GAZ-3102 Volga car

The movement of the GAZ-3102 Volga car during the delay of the driver (65.5 m) is approximately 1.5 times greater than the movement of the ZIL-130-76 car (41.0 m). Therefore, his driver had the technical ability to avoid a collision. The driver of the ZIL-130-76 car did not have such an opportunity.

When considering ways to prevent a cross collision in the same way as above, it is determined whether the driver had time to perform the necessary actions when an objective opportunity arose to detect the danger of a collision. The driver enjoying the right of way must take the necessary safety measures from the moment he can determine that another vehicle may be in his vehicle's lane when moving further. The moment of occurrence of a dangerous situation must be determined by the investigation or the court, since when this moment is subjectively determined, conflicting interpretations and significant errors are possible. For example, in some methodological sources there is an indication that a dangerous situation arises at the moment when the driver of a car can detect another vehicle at such a distance at which its driver can no longer stop to give way (i.e. when another vehicle the vehicle has approached a distance equal to the braking mark). To put this situation into practice, the driver must accurately determine the speed of the approaching vehicle, its braking properties and the quality of the road, calculate the length of the braking distance and compare it with the actual distance observed by him. The unreality of such an operation is obvious.

When analyzing collisions at closed intersections, visibility limitations are taken into account using an offset calculation methodology similar to that described in Chap. 5.

Control questions

1. What is the recovery factor? How does he characterize

impact process?

2. Describe central and eccentric impacts.

3. How does the speed of a car change when it hits a rigid, stationary obstacle?

4. How to determine the initial speed of a car before hitting a stationary obstacle: a - with a central impact; b - with an eccentric impact?

5. In what sequence are car collisions analyzed?

6. How to determine the possibility of preventing a passing collision (oncoming collision)?