Determining the angle of collision of vehicles from a photograph. Transport-trasological expertise. When colliding with another object, an "External Force" is generated

The location of damage to the vehicle from contact with each other makes it possible to determine their relative position at the moment of collision and clarify the place of collision if the location and direction of movement of one of them at the moment of collision are established.

Sometimes the angle is determined from photographs of damaged Vehicle. This method gives good results only when pictures of different sides of the car are taken at right angles from the same distance. Due to the fact that carrying out measurements of the deformation of the vehicle and taking photographs to determine the angle of collision require certain skills and knowledge, it is advisable to carry them out with the participation of experts.

The direction of deformations, which determines the direction of impact, allows you to set the possible displacement of the vehicle from the place of collision, and by its location after the accident, to clarify the place of the collision.

The nature of the deformations makes it possible to set the collision angle of the vehicle and by calculation to determine the value of the interval between the moving parallel courses of the vehicle before turning one of them onto the lane of the other (based on the maximum adhesion of the turning radius). This allows you to specify the location of the collision according to the width of the lane.

Rice. 4. Types of location of vehicles at the time of the accident.

The location of damages on the lower parts of the vehicle, which left tracks on the road during a collision, makes it possible to clarify the position of the vehicle by the width of its lane when these tracks were formed at the collision site.

The study of damage to painted and metal parts allows you to establish the direction of movement of colliding vehicles. Marks on the surface of a damaged car that are wider than deep and longer than wide are called scratch marks. The scratches run parallel to the damaged surface. They have a small depth and width at the beginning, expanding and deepening towards the end. If the primer is damaged along with the paintwork, then it exfoliates in the form of wide, drop-shaped scratches, 2-4 mm long.

Damage that is deeper than the width is called scuffing and denting. The depth of the scratch usually increases from its beginning to the 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, which are bent in the same direction in which the scratching object moved. The slower car has scratch marks from the back to the front, while the overtaking car has the opposite direction.

In a head-on collision, the speeds of the cars cancel each other out. If their mass and speed were 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 lighter is thrown back. In the event that the driver of a truck at the time of an accident does not take his foot off the gas pedal and, confused, continues to press it, then the truck can drag an oncoming passenger car a fairly long distance from the collision site.

Place of collision. To restore the mechanism of an accident associated with a collision of cars, it is necessary to determine the place of the collision, the mutual position of the cars at the time of the impact and their location on the road, as well as the speed of the cars before the impact. The initial data provided to the expert in such cases are usually incomplete, and there is no reasonable methodology for determining the necessary parameters. Therefore, in the analysis of collisions, as a rule, it is not possible to give an exhaustive answer to all the questions that arise. The most accurate results are obtained by the joint activities of experts of two specialties: a forensic specialist (trasologist) and an automotive technician. However, the experience of such work is still small and an expert auto technician often has to perform the functions of a trace expert.

The position of the collision site of cars on the roadway is sometimes determined based on the testimony of participants and eyewitnesses of the accident. However, the testimonies, as a rule, are inaccurate, which is explained by the following reasons: the stressful state of the participants in the accident; the short duration of the collision process; the absence of fixed objects in the accident area, by which drivers and passengers can fix in memory the place of the collision; involuntary or deliberate distortion of the circumstances of the case by witnesses.

In addition, there may not be witnesses to the accident.

Therefore, to determine the location of the collision, it is necessary to examine all the objective data that resulted from the incident. Such data, allowing the expert to determine the location of the collision site on the roadway, can 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), accumulation of glass and plastic fragments, dust particles, dirt that fell off the lower parts of vehicles during a collision;

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

characteristics of damage received by vehicles in the process of collision;

location of vehicles on the roadway after an accident.

Rice. 7.9. Tire tracks on the road:

a-sliding trace (skid), b-rolling trace, c-cross-sliding trace, d-change of traces during a cross 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 the expert is given by tire tracks on the road. They characterize the actual position of vehicles on the roadway and their movement during an accident. Between the collision and inspection of the scene of an accident, such traces usually change little. 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. So, 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 an accident. The most characteristic 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 time of the impact can sometimes be determined by the change in the nature of the tire tracks. So, in case of off-center oncoming and transverse collisions, the tire tracks at the collision site are displaced in the transverse direction in the direction of the car (Fig. 7.9, d).

In an oncoming collision, 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 can be unlocked for a moment, since the adhesion force will exceed the braking force (Fig. 7.9, e).

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

a - asphalt concrete, b - cement-concrete

If the shock load is directed from the bottom up, then the wheel can come off the road. Sometimes, on the contrary, the wheel at the moment of impact is wedged by the deformed parts of the car and, having stopped rotating, leaves a tire mark on the road, usually a small one.

Parts of the body, chassis and transmission of the car, destroyed by impact, can leave marks on the surface in the form of potholes, furrows or scratches. The beginning of these traces is located, as a rule, not far from the collision site. The same traces are left by parts (footboards, pedals, steering wheel) of an overturned motorcycle, scooter and bicycle when dragged or thrown away during an accident. Scratches and furrows on the coating begin with an inconspicuous trace, then its depth increases. Having reached the maximum depth, the track ends abruptly (Fig. 7.10). A tubercle is formed on the asphalt concrete pavement at the end of the dent due to plastic deformation of the mass.

In some cases, particles of its mass remain on the parts of the car that damaged the coating. Identification of these particles makes it possible to refine the part that has come into contact with the coating.

Some idea of ​​the location of the collision can give the trajectory of objects thrown in the process of collision. These trajectories may be different depending on the shape and mass of objects, as well as on the nature of the road. Objects that are round and close to them in shape (wheels, caps, headlight rims), rolling, can move a long distance from the place of fall. A pothole or elevation on the surface creates a local increased resistance to the movement of the object, contributing to its unfolding and curvature of the trajectory. However, the initial sections of the trajectories are usually close to rectilinear, and in the presence of several traces located at an angle, it can be assumed that the collision site is located near the point of their intersection.

After a collision of vehicles on the road

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

Very often, when cars collide, glass and plastic parts are broken, the fragments of which scatter in different directions. Part of the fragments falls on the parts of the car body (hood cover, fenders, steps) and bounces off them or moves along with them, after which it falls onto the road. Glass particles that are in direct contact with the 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 moved from the point of impact 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.

In the area of ​​an accident, as a rule, there are many signs, each of which in its own way characterizes the position of the collision site. However, none of these signs, taken separately, can serve as a basis for a final conclusion. Only a comprehensive study of the entire set of information allows the expert to solve the tasks assigned to him with the necessary accuracy.

P
position of cars at the moment hit. All variety of vehicle collisions depending on the 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 are moving in parallel or close courses, - passing(Fig. 7.11, /// and IV). At st 90° collision is referred to as cross(Fig. 7.11, V), and at 0<st<90° (рис. 7.11,vi) and at 90°<st<180° (рис. 7.11,VII) -oblique.

Fig 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 direct; if it falls on the sides, - sliding(see fig. 7.11, // and IV).

Fig 7. 12. Angle detection st

The position of cars at the moment of impact is often determined by investigative experiment on the deformations resulting from the collision. To do this, damaged cars are placed as close as possible to each other, trying to combine 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 sections are located at equal distances from each other (Fig. 7.12, b). Since such an experiment is quite difficult to carry out, cars are sometimes drawn on the scale of the diagram and, having applied damaged zones on them, the collision angle is determined graphically.

These methods give good results in the examination of head-on cross-collisions, when the contact areas of the cars during the impact do not have a relative movement. In oblique and angular collisions, despite the short duration of the impact, the cars move relative to each other. This leads to slippage 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, the Rud force arises at the place of initial contact, which, together with the inertia force, gives a moment that tends to turn the passenger car in the clockwise direction. The car, rotating, sequentially takes positions I... IV, which leads to the appearance of an extensive deformation zone of both vehicles (we conditionally consider the truck to be motionless). If we define the angle Using the methods described above (Figure 7 13, b), one can come to the wrong conclusion that the cars at the initial moment of impact were located at an angle of about 35 °.

Rice. 7.13. Off-center collision of cars:

a - collision process;

b - wrong angle definition st,

Figure 7.14. Damage to the surface of the car in collisions

a - scratches when peeling the primer, b - burrs on the scuff

Sometimes the corner 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 about the ratio of the speeds of colliding vehicles and the direction of their movement can be obtained by examining the 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. The scratches run parallel to the damaged surface. They have a small depth and width at the beginning, expanding and deepening towards the end. If the primer is damaged along with the paintwork, it will peel off in the form of wide teardrop-shaped scratches 2-4 long mm. The wide end of the drop is directed towards the 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). Damage, the depth of which is greater than their width, is called scuffing and dents. The depth of the scratch usually increases from its beginning to the 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 scratching object moved.

Knowing the direction of movement of the object that caused the scratch or scuff (indicated by an arrow in Fig. 7.14), the expert determines which of the cars moved at a higher speed during a passing sliding impact. In a car moving more slowly, the scratch marks are directed from the back to the front, and in the overtaking car - 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 a head-on 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 lighter is thrown back. Sometimes the driver of a truck before a collision does not take his foot off the throttle pedal 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.

Gliding 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 the collision, they could drive far away from the collision site.

At the moment of impact of cars of 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 move in the same direction. Although after the termination of the impact loads, the vehicles move under the influence of external forces and in the future the trajectories of both vehicles may change, however, the general direction of movement of the centers of gravity makes it possible to determine the position of the vehicles at the time of the collision.

Determination of vehicle speed before impact It is usually quite difficult, and sometimes impossible, to determine the initial speed of a car on the basis of the data contained in the materials of a criminal case. The reasons for this are the lack of a universal calculation method suitable for all collision variants, and the lack of initial data. Attempts to use the recovery factor in these cases fail

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

a - both the car is not braked;

b - both cars are braked;

in - the front car is braked;

d - the rear car is braked

lead to positive results, since no reliable values ​​​​of this coefficient in a collision have been published. When investigating vehicle collisions, the experimental value cannot be applied. To oud , valid for a car hitting a hard obstacle. The processes of deformation of parts in both cases are fundamentally different, respectively, the recovery coefficients should also be different, as evidenced, for example, in Fig. 7.6. The ability to accumulate 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 have proposed an empirical formula for the recovery factor

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 can differ from the actual ones by several times. Therefore, the formula can be recommended only for purely indicative calculations, and not for use in expert practice, especially since it describes accidents with foreign cars.

The lack of reliable information about the recovery factor often forces experts to consider the limiting case, considering the impact to be absolutely inelastic. (TO oud =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 \u003d 0. After the impact, both cars move as one with a 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 the initial speed U" 1 .

The kinetic energy equation in this case

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

Therefore, U" 1 =
. Moreover, according to formula (7.2) for U 2 =0 and U" 1 =U" 2 the speed of car 1 before impact

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

Vehicle speed after impact U" 1 =
.

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

Vehicle speed 7 at the start of the braking distance

where S u1 is the length of the skid track of car 1 before the impact.

Vehicle speed 1 before braking

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

Both cars after the impact move the same distance S mon 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. Parking car 2 not slowed down. The rear car 1 before the impact in the inhibited state moved a distance S u1 . After the impact, the displacement of car 1 is S Mon1 , and the movement of the car 2 - S pn2.

Similar to previous cases

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

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

In a cross-collision (Fig. 7.17, a) both cars usually make a complex movement, since as a result, each of the cars begins to rotate around its center of gravity. The center of gravity, in turn, moves at a certain angle to the original direction of motion. Let the drivers of cars 1 and 2 braked before the collision, and brake marks are recorded on the diagram S 1 and S2.

Figure 7.17. Car collision patterns

a - cross,

b - oblique

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

The total amount of movement 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 movement in each of these directions will not change, then

(
7.18.)

where U" 1 and U" 2 - car speeds 1 and 2 after impact

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

The work of tire friction on the road during the forward movement of the car 1

The same when turning it relative to the center of gravity by 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 car 1, 1 - angle of rotation of the car 1, rad

where L" - base car 1 Therefore,

Hence the speed of the car 1 after collision

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

where L" and 2 - respectively the base and the angle of rotation of the car 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 the car 1

Same for car 2

Knowing the speeds U 1 and U 2 of cars immediately before the collision, it is possible, using expressions (7.16) and (7.17), to find the speeds at the beginning of the braking distance and before braking.

When calculating, it should be borne in mind that the distances (S pn1 and S pn2) and angles (Ф 1 and Ф 2) characterize the movement of the centers of gravity of cars. The distances S pn1 and S pn2 can differ significantly from the length of the tire tracks on the pavement. 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 from a diagram drawn to scale, marking the position of the center of gravity of each vehicle involved in the accident.

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

Then, according to Fig. 7.17b:

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 parts of equations (7.22) and (7.23), respectively, through BUT 1 and B 1 , you can find the speeds of the cars before the impact:

The speeds of the cars before the cross-collision, determined by the described method, are the minimum possible, since the calculations do not take into account the energy spent on the rotation of both cars. Actual speeds can be 10-20% higher than calculated ones.

Sometimes the so-called "reduced" speed of the car is used, that is, the speed at which the car, having run into a fixed obstacle, receives the same destruction and deformation as in a collision. Of course, there are no fundamental objections to such a parameter, but there are no reliable methods for determining it.

Technical ability to prevent a collision. The answer to the question of whether it is possible to prevent a collision is related to determining the distance between cars at the time of the occurrence of a dangerous traffic situation. It is difficult, and often impossible, to establish this distance by expert means. The information contained in investigative documents is usually incomplete or contradictory. The most accurate data is obtained by an investigative experiment with a trip to the scene of an accident.

Consider first the passing collision.

If the collision was the result of the sudden braking of the front car, then with a working brake system of the rear car, there can be only two reasons: either the driver of the rear car is late, or the distance chosen by him is incorrect. With a correctly chosen distance and timely braking of the rear car, a collision is obviously excluded.

If the actual distance between cars S f is known, then it is compared with the distance S b , the minimum necessary to avoid a collision. If the brake light of the leader car is in good condition and turns on at the moment the driver presses the brake pedal, then the minimum distance according to safety conditions 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 , THEN S b \u003d U a+ U 2 a(1/j""-1/j")/2.

The greatest safe distance should be when following a truck behind 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 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 when S F < S b - conclusion that he did not have such an opportunity.

For some vehicles, 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 of them have time to slow down and stop the cars. If at least one of the cars does not stop, an accident will be inevitable.

Consider the possibility of preventing a head-on collision Figure 7.18 shows 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 traffic 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,

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

IV- at the time of the 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 (presumable version).

Figure 7.18. The graph of the movement of the car in an oncoming collision

The distance between the cars at the time of the occurrence of a dangerous situation 5v. Section //-/// corresponds to the movement of cars with constant speeds for the total time T 1 (T 2 ). The distances S a 1 and S a 2 separating the cars from the collision site at the initial moment must be determined by the corollary, just like their initial speeds U a 1 and U a 2 .

Obvious condition for being able to avoid a collision: the visibility distance must not be less than the sum of the stopping distances of both vehicles:

S in \u003d S a1 + S a2 So 1 + So 2 , where indices 1 and 2 refer to the respective vehicles. To implement this condition, drivers must simultaneously react to the danger to traffic that has arisen and immediately initiate emergency braking. However, as expert practice shows, this rarely happens. Typically, drivers continue to approach for a while without slowing down, and brake with a significant delay, when a collision cannot be avoided. Such accidents are especially frequent at night, when one of the drivers drives to the left side of the road, and insufficient lighting makes it difficult to determine distances and recognize vehicles.

In order to establish a causal relationship between the actions of the drivers and the resulting consequences, it is necessary to answer the question: did each of the drivers have the technical ability to prevent a collision, despite the wrong actions of the other driver? In other words, whether a car collision occurred if one of the drivers 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 respond in a timely manner to a dangerous situation. After that, the position of the second car is found at the moment of stopping, if it had not been delayed in a collision.

Collision avoidance capability condition for the driver of vehicle 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.

An approximate sequence of calculation when evaluating the actions of the driver of car 1 is as follows.

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

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

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

3. The distance that the second car would have traveled to the stop from the point of collision if there had been no collision,

where S u2 is the length of the skid mark left on the pavement by the second car in front of the collision site.

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

5. Condition for the possibility for the driver of the first car to avoid a collision, despite the untimely braking of the second driver: S a 1 So 1 + S mon2.

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 the road with a width of 4.5 m, there was a head-on collision of two cars: 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 inspection of the scene of the accident, 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. assess the traffic 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 the availability of technical capabilities to prevent a collision of cars for each of the drivers.

Solution.

1. Stopping ways of the car ZIL-130-76 So 1 =15*l, 4+ 225/(2*4.0) =49.5 m; car GAZ-3102 "Volga" 5 „2 \u003d 25 * 1.2 + 625 / (2 * 5.0) \u003d 92.5 m.

2. Collision avoidance condition: 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. Therefore, if both drivers had correctly assessed the traffic situation and at the same time made the right decision, then the collision could have been avoided. After the cars stopped, a distance of about 58 m would remain between them: S \u003d (80+ 120) - (49, 5 + 92, 5) \u003d 58 m.

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

3. The speed of the car GAZ-3102 "Volga" at the moment of the beginning of full braking U u2 \u003d 25-0.5 * 0.2 * 5, 0 \u003d 24.5 m / s.

4. The path of full braking of the car GAZ-3102 "Volga" S "" 4 \u003d 24.5 2 / (2 * 5.0) \u003d 60.0 m.

5. Movement of the car GAZ-3102 "Volga" from the collision site in a braked state in the absence of a collision S n2 = 60.0 -22, 0 ==38.0 m.

6. The condition for the possibility for the ZIL-130-76 driver to prevent a collision: So 1 + S pn2 \u003d 49.5 + 38.0 \u003d 87.5> S a 1 \u003d 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 car 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 reacted untimely to the appearance of danger and both braked with some delay, but only one of them had the opportunity to prevent a collision in the situation that had developed, and the second did not have such an opportunity. To explain the resulting conclusion, we determine the movement of each car for the time overdue by its driver.

Moving the car ZIL-130-76

Moving the car GAZ-3102 "Volga"

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.

Considering the ways to prevent a cross-collision in the same way as above, it is established whether the driver had time to perform the necessary actions when an objective opportunity arose to detect the danger of a collision. A driver enjoying the right of way to traffic must take the necessary safety measures from the moment when he can determine that another vehicle, in further movement, may be in the lane of his car. The moment of occurrence of a dangerous situation must be determined by the investigation or the court, since subjective determination of this moment may lead to conflicting interpretations and significant errors. So, for example, in some methodological sources there is an indication that a dangerous situation arises at a moment when a car driver 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 wake). In order to put this provision into practice, the driver must accurately determine the speed of the approaching vehicle, its braking properties and the quality of the road, calculate the stopping 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 restrictions are taken into account, using a removal calculation method similar to that described in Chap. 5.

test 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 the car change when it hits a rigid immovable obstacle?

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

5. In what sequence are car collisions analyzed?

6. How to determine the ability to prevent a passing collision (oncoming collision)?