The reaction time of the driver is the most important characteristic that determines the level of traffic safety. It often happens that it is the speed of making and the correctness of the decision in the event of a threat of an emergency, as well as the time of their implementation, that directly affect the occurrence of an accident.
Interesting! Reaction is the body's response to an external stimulus.
Driver reaction time, definition
The speed of the driver's reaction in the SDA is the period of time, the countdown of which begins at the moment the driver detects a potential danger and before the start of taking measures aimed at avoiding the danger. Measures mean pressing the brake pedal or turning the steering wheel.
Reactions are divided into simple and complex. Simple responses are responses to a single stimulus. Such an irritant can be the braking of the car in front. A complex reaction is a response to several stimuli at once. An example would be a regulated intersection, where the driver must not only comply with traffic signal requirements, but also watch for other vehicles and yield to pedestrians.
Steps of the reaction process
The driver's reaction is divided into three stages:
Assessment of the situation
In this phase, the driver must constructively evaluate what is happening. Do not fuss or panic, it can only hurt.
Decision-making
The driver must decide what actions he must take to avoid getting into an accident.
response
The driver performs the action that, in his opinion, is the most appropriate in this situation.
Important!To achieve the safest possible driving, the driver must be able to react quickly to the traffic situation.
The average value, and what determines the reaction time of the driver
When a driver gets into an extreme situation, he has a few seconds to realize what is happening and make the right decision. It is generally accepted that the average driver reaction time is 1 second. To date, during the examinations, a standard driver reaction time of 0.8 s is used. However, everything is relative. For example, for normal braking, the driver spends 0.5 seconds, during which time he transfers his foot from the gas pedal to the brake pedal. In the case of a more extreme situation, for example, you need to make a detour, actions with control are connected, and the time to complete them increases.
F. ERMAKOV
F. Ermakov, Professor of the Department of Life Safety, Kazan State Agricultural Academy, Doctor of Technical Sciences.
When investigating a vehicle collision with a pedestrian, standing cars and various immovable obstacles, the forensic autotechnical expert and the investigator must decide whether or not there is a possibility to prevent the incident, and the prosecutor and the judge must make sure that their decision is correct. To do this, the expert calculates the stopping distance of the vehicle at the speed established by the investigation or the expert. The stopping distance is compared with the distance at which a pedestrian appeared or there were standing vehicles and immovable obstacles. The investigator, the prosecutor and the judge must check and evaluate the reliability and objectivity of the initial data used by the expert for calculating the stopping distance and the conclusion of the auto technical expertise.
In calculating the stopping distance of a vehicle, in addition to its speed, a psychophysiological parameter is taken into account - the driver's reaction time to danger - and technical parameters related to the car and road conditions, which, according to technical literature, have limiting values - minimum and maximum values. However, when investigating road traffic accidents (RTA), it has become such a practice that, as a rule, experts carry out calculations of the stopping distance of vehicles involved in an accident with average values of psychophysiological and technical parameters.
Investigators, prosecutors and judges, when assessing the reliability and objectivity of expert opinions, often do not pay attention to this, which is primarily due to ignorance of technical issues and a lack of understanding of the influence of the limiting values of the calculated parameters on the conclusions about the presence or absence of the possibility of preventing an accident.
So, the calculated parameters have limiting values - the minimum and maximum values. According to technical literature, the driver's reaction time to danger ranges from 0.4 to 1.2 seconds. Experts in the calculations take it equal to 0.8 seconds. For example, we point out that the stopping distance of a passenger car on a horizontal road section with a dry asphalt concrete surface at a speed of 60 km/h and the indicated values of the reaction time is 36.73; 43.4 and 50.06 m. If a pedestrian appeared at a distance of 45 m, then in the first and second cases it is possible to prevent a collision with a pedestrian, since 36.73 and 43.4 m are less than 45 m, in the third - there is no such possibility (50.06 m is more than 45 m). From this comparison of the stopping distance of the car with the distance to the pedestrian follows one of the proofs of the guilt or innocence of the driver.
Taking into account the fluctuation of the response time to danger for different drivers, which leads to a difference in the values of the stopping distance of the car (in our example, up to 36.29%), the investigator must raise the question of establishing the presence or absence of the possibility of preventing an accident, for example, a collision with a vehicle on a pedestrian, in two versions - with a reaction time to the danger of 0.4 and 1.2 seconds. If in both cases the same conclusion is obtained about the possibility of preventing the incident, then it should be used for further investigation. If the conclusions are contradictory, the investigator must appoint a comprehensive engineering and psychophysiological examination, raising the question of determining the actual value of the response time of this driver to danger for its resolution. The appointment of the specified expert examination must be requested by the prosecutor when verifying the correctness of the termination of the criminal case or approving the indictment. Of course, it would be advisable to do this not at the end of the investigation of the case, but in its course. If necessary, such an examination may be appointed by the court.
The need for this examination has been proven by our experimental studies of the reaction time to danger for a large number of car drivers. As a result of the research, it was found that the time of their reaction to danger during a 7-8-hour working day has a relative psychophysiological constancy. It has also been proven that the driver's reaction time to danger obeys the law of normal frequency distribution. This allows, according to experimental studies, to determine statistically significant limit values - the minimum and maximum values of the response time of each individual driver to danger at different probabilities.
The established relative psychophysiological constancy of the driver's response time to danger is fixed by the patent for invention N 2134062 issued to the author in 1999 "Method for determining the professional suitability of an operator to control moving and stationary objects." It establishes that the maximum permissible value of the reaction time of vehicle drivers to danger with a probability of 0.997 (99.7%) is 1.3 seconds. The driver's response time to danger should be determined using appropriate experimental equipment during initial and periodic medical examinations for the suitability of driving a car, and its limit values obtained by mathematical processing should be recorded in the medical certificate of the subject along with the indicators of vision, hearing, nervous system and etc.
If in the calculation of the stopping distance of the vehicle, the value of which is the basis for deciding whether there is or is not the possibility of preventing an accident, we take the driver's reaction time to danger equal to 0.7 ... 0.8 seconds, then this provides only 50% confidence that such time may be available to the driver who caused the accident; if we take 0.8 ... 0.9 seconds, the confidence will be 68%; 0.9 ... 1.1 - 95%; 1.1...1.3 - 99.7%.
The use of these recommendations in forensic and investigative practice will make it possible to make objective decisions on specific accidents, to eliminate errors in determining the perpetrators.
Russian justice, N 9, 2001
Suppose we have decided on the moment of occurrence of danger and have all the necessary initial data to determine whether or not the driver of the vehicle has the technical ability to prevent an accident. To solve this issue, the expert has a number of expert methods, both for general and private traffic situations. If the expert has certain initial data, the solution of this issue does not cause any technical difficulties.
However, the question arises: for all the seeming simplicity of solving the problem, does an expert always have the right to draw categorical conclusions, which can later form the basis of a sentence or a court decision?
The solution to this issue, in the classical case, comes down to comparing the full stopping distance of the car during emergency braking in given weather and road conditions with the removal of the car from the collision (collision) site at the moment of danger to its movement.
Consider the simplest case: 1. Deletion is given; 2. Vehicle speed; 3. The absence of traces of its braking. Then it remains for the expert to determine the stopping distance of the car using the well-known formula:
S o = (t1 + t2 + 0.5 t3) V a + V a 2 / (2 j) [m],
and compare it with deletion.
As you know, when studying the circumstances of an accident, the theory of SATE requires an expert to solve problems in the system driver - car - road - environment (VADS). From these positions, the above formula can be represented as a sum consisting of two terms:
With term No. 2 all clear. It contains technical parameters and, for example, reliable data on the speed of the vehicle.
Term No. 1 is the product of t 1 V a - the distance traveled by the car during the time elapsed from the moment of danger to movement until the moment of braking. At the set vehicle speed, the value of this term depends only on the driver's reaction time, the experimental and calculated value of which, depending on the DTS, is taken by the expert, mainly from the methodological recommendations "Application of differentiated values of the driver's reaction time in expert practice", developed at VNIISE back in 1987.
However, the functional qualities of a driver depend on many unrelated reasons, and is it possible to use the average estimated values of these qualities in a particular case?
The driver's control actions are his responses to the perception of the road, pedestrians, other vehicles, road signs, indications of instrumentation, etc. These actions are carried out by movements of the steering wheel, gear lever, clutch pedals, brakes and other operating controls.
The most complex and typical activity of the driver is sensorimotor coordination, in which not only the perceived stimulus is mobile, but also the motor actions of the driver himself are dynamic. Each of his control actions is not just a chain of individual reactions. They are interconnected by sensorimotor coordination, in which movement is regulated by perception, and it, in turn, changes as a result of the movement made. For example, upon perception of a vehicle approaching an intersection, the driver slows down. After performing the necessary actions for this, the position of the vehicle may change, and, therefore, a new perception of the changed situation will be required.
Responses to stimuli are called sensorimotor reactions .
In the sensorimotor reaction, the processes of perception, processing of perception and the motor moment, which determines the beginning of movement, are distinguished. In each reaction, latent, or latent, and motor periods are distinguished.
latent period - this is the time from the moment the stimulus appears to the start of movement.
motor period is the time of execution of the motor act.
Some figures: the average latency period for a simple reaction to a light signal is approximately 0.2 s, to a sound signal - 0.14 s. For the perception and processing of information, the operator spends on average: 0.1 s for signal detection, 0.28 s for eye fixation; recognition of a simple signal - 0.4 s; reading indications of pointer devices - 1 s; perception of numbers, banners - 0.2 s; perception of a seven-digit number - 1.2 s.
The latent period of a complex reaction varies widely and depends on the traffic situation and, consequently, on the complexity of the choice when making a decision, as well as on the individual psychophysiological characteristics, experience and condition of the driver.
When driving a car, it is necessary not only to perceive various objects, but also to evaluate their location, the distance to them and between them, which is provided by spatial perception. The driver must have a perfect perception of space, without which it is impossible to safely drive a car. Spatial perception allows the driver to correctly assess the position of pedestrians, cars and other road users, which helps him determine his behavior. Spatial perception includes visual acuity, visual field and depth vision.
Visual acuity is the ability of the eye to distinguish the details of large objects or small objects at a considerable distance from them. The greatest visual acuity is central vision in a cone with an angle of 3-4º, good - in a cone with an angle of 7-8º, satisfactory - in a cone with an angle of 13-14º.
Objects located outside the 14º angle are visible without clear details and color. Visual acuity to the periphery is reduced by 4 times. It has been established that 80-90% of the time the driver's gaze is directed to the road, while he uses his central vision. However, for the perception of the traffic situation, it is necessary to shift the gaze to the zones of peripheral vision, which requires a certain amount of time. So, when crossing the intersection, it takes 0.15-0.26 s to shift the gaze to the left, 0.10-0.30 s to fix on the left side, 0.15-0.30 s to shift to the right, and to fix the gaze on the right side - 0.10-0.30 s. The total time of looking away from the road is 0.5-1.16 s.
The field of view is the space that a person can cover with a glance when the eyes are stationary. The field of view for white color with two eyes (binocular vision) is 120-130º and covers the entire space in front of the car. The field of view depends on the color of the object being viewed. For green, the field of view is almost two times smaller than for white; for red and blue, it decreases by 10-20º compared to white. The narrowing of the visual field may be the result of a birth defect or a past disease.
Depth vision is a vision characterized by the ability to distinguish between the relative and absolute distance of the observed objects. The most correct perception of space is achieved by knowing the size of objects that are often encountered along the way, which, in turn, directly depends on the experience of the driver.
The length of the motor period depends on the complexity of the response being performed. These actions in a complex reaction can be combined in various combinations. For example, pressing the brake pedal of a car and turning the steering wheel at the same time. Since motor actions during braking are worked out quite well by drivers due to constant training in the process of driving a car, the reaction time during emergency braking mainly depends on the time of its latent period.
Thus, as a result of the research, it was found that the average reaction time during emergency braking is from 0.3 to 4 s. However, this indicator, depending on subjective and objective factors, can fluctuate within fairly wide limits.
Subjective factors include the level of professional and physical fitness, health status, age, gender, temperament, self-control, stability and intensity of attention, medication and other personal factors.
Objective factors are visibility, the complexity of the road situation and its unexpected change, speed, time of day, meteorological factors, geomagnetic solar activity, etc.
Consider how individual factors affect the overall reaction time of the driver.
When measuring the reaction time of drivers on a device designed at MADI, when the subject, at the “Attention” command (on a car simulator), must press the gas pedal and, if the red signal lamp suddenly lights up, move the foot to the brake pedal as quickly as possible and press it, the researchers it was found that the average reaction time of experienced drivers who have driven 50 thousand km is 0.5 - 1.5 s, and drivers with less experience - 1.0 - 2.0 s.
The reaction time increases with fatigue, with a painful condition and after drinking alcohol. So after 6 - 8 hours of driving, the reaction time increases by 0.1 - 0.2 s.
The reaction time in choleric people, as shown by special studies, turned out to be 25-35% less than in phlegmatic people, but they have more errors. Since choleric people are more prone to hasty and premature actions.
Reaction time increases in older people. According to some studies, at the age of 60, the time of a simple reaction increases by 60 - 65%, and the time of a complex one - by 31 - 38%. The latter is explained by the fact that in case of complex reactions, when it is necessary to choose a solution from a number of possible ones, the professional experience of older drivers affects, who quickly identify the object on the road that creates an emergency situation, and better predict the way out of an emergency situation. The minimum reaction time of drivers in the 40-50 age group is twice the reaction time of a 20-year-old driver.
The average reaction time in men is shorter than in women. The time of complex reactions in women increases in the menstrual cycle, which is associated with a weakening of attention and a decrease in muscle tone.
An increase in reaction time is also noted when driving in conditions of limited visibility, especially at night. On average, in the dark time of the day, the reaction time increases by 0.6 - 0.7 s. This is due to the fact that in poor visibility it takes more time to perceive objects on the road, which increases the latent period of the reaction.
At night, visual acuity decreases sharply, deep vision is disturbed, and the field of view narrows. All this complicates the spatial perception of the driver. Even on a full moon, visual acuity drops by 2 times, and when it is cloudy, by 20 times! According to other sources, on a bright night, visual acuity decreases to 30-70%, and on a dark night - up to 5 or even 3%. The sharpness of night vision is especially reduced in older drivers. If the average visual acuity at the age of twenty is taken as 100%, then at 40 years old it is 90%, at 60 years old - 74%, and at 80 years old - 47%.
Violation of deep vision leads to the fact that the driver incorrectly determines the distance to the obstacle that has appeared on the road, makes mistakes in assessing the width of the road. Thus, it has been established that during the day the error in determining the distance to an oncoming car is 5-10% by 100 m, and 25% at a distance of up to 1 km. At night, this error increases by 2-3 times.
In addition, at night, the reaction time is affected by the daily biorhythm. Man in the process of long evolution led an active lifestyle during the day and slept at night. Therefore, at night, all life processes proceed at a lower level, which slows down perception, thinking, and, consequently, psychomotor reactions, the time of which, on average, increases by 75-100%.
The reaction time also increases with an increase in speed, since when objects move quickly, perception is difficult and occurs more slowly, which leads to an increase in reaction time. For example, with an increase in the speed of movement from 50 to 70 km / h, the reaction time increases from 1.1 to 1.7 s.
The reaction time also depends on road conditions, so the average reaction time generally accepted abroad is not the same on different roads. For example, in Switzerland, on motorways with a median, the average reaction time is 2 s, and on ordinary roads - 1 s. In Australia, in the city - 0.75 s, outside the city - 2.5 s.
Climatic conditions also affect the reaction time. An increase or decrease in temperature worsens the driver's well-being and reduces his performance. At a high temperature, the functions of thinking, attention, memory are disturbed, time increases and the accuracy of sensorimotor reactions decreases. As a result, the driver fails to notice changes in the road situation, is late in performing the necessary control actions, makes mistakes, and gets tired faster.
A decrease in the speed and accuracy of motor reactions at low temperatures occurs due to a deterioration in muscle function. This is expressed in stiffness and inaccuracy of movements.
Measurements carried out in Central Asia showed that an increase in ambient temperature to 43ºС increases the reaction time by 30-40%.
Thus, from the foregoing it follows that the actual value of the driver's reaction time in most cases will exceed the values used by experts in the production of STE. Obviously, the use of a differentiated value of the driver's reaction time in expert practice reduces the objectivity and reliability of the SATE. A forensic expert - an auto technician does not have special knowledge in the field of the individual psychological qualities of the driver, the influence of stress factors and other psychological circumstances related to the personal qualities of the driver as a whole.
Obviously, under such circumstances, if we accept the reference values of the reaction time as the minimum possible in a given DTS, only the answer that the driver has no technical ability to prevent an accident can be categorical. Otherwise, the conclusion can only be probable, for example: "the driver of the vehicle could have had the technical ability to prevent an accident if his reaction time in this DTS did not exceed the accepted reference value." At the same time, according to the current legislation, the expert has the right and is obliged to inform the person or body that appointed the forensic examination about the need to appoint a comprehensive examination on this issue with the involvement of a specialist in engineering and psychophysiological examinations and setting tasks for him to determine the driver’s reaction time, depending on specific circumstances of the road situation preceding the accident.
The reaction time of the driver is understood as the time separating the signal about a change in the traffic situation, received by the driver's senses, and the beginning of its impact on the vehicle controls.
Simple wording, right? Meanwhile, it almost does not reveal the features of the driver's reaction, the time spent on it in different conditions, as well as in the same situation, but under the influence of different factors. All this is necessary to know in order to minimize the likelihood of a traffic accident. Knowledge in this case is truly a power that saves human lives. The complete signal flow diagram is as follows. Changes in road conditions are perceived mainly by the driver's organs of vision. (The exception is situations when the source of danger is out of the driver's field of vision; then the decision-making time is counted from the perception by the hearing organs.) A set of signals enters the driver's central nervous system, where, based on them and on the basis of the sum of acquired knowledge and experience, an answer is formed - in the form of a series of actions performed by the driver with the steering wheel, brake pedal, etc. However, the human body is the most complex biological system, and the instantaneous passage of a danger signal through it is almost impossible. Suffice it to mention the time it takes to process information in the brain. Now, during the examination, the standard driver reaction time is used, equal to 0.8 s. But real life is always strikingly different from theoretical calculations. For example, ideally, for braking, the driver only needs to move his foot from the gas pedal to the brake pedal - and spend no more than 0.5 seconds on it. If you need to make a detour around an obstacle, the control actions will be more difficult, respectively, and the time to complete them will increase ...
In terms of reaction time, male drivers are slightly better than women - by about 0.05 s. Beautiful halves, however, are ahead in terms of control accuracy. Age Young people are faster at detecting signals and processing information. However, the elderly spend less time making the right decisions, moreover, their reaction time is more stable.
Experience
No knowledge of traffic rules and technology will replace the driver's "experience, the son of difficult mistakes." An experienced driver can be immediately recognized by a calm, disciplined, confident, sometimes even intuitive driving. The ability to predict the situation on the road, acquired over the years, significantly reduces the reaction time of an experienced driver.
Fitness
Regular exercise and sports have a healing effect on the body. As a result, physically healthy drivers react faster to danger.
Working conditions
Urban traffic is a constant change in the traffic situation. Therefore, the driver, setting himself up for this in advance, reacts better to a sudden danger than “lulled” by a long and monotonous intercity route.
Times of Day
Night is a time of limited illumination, which even the most intense artificial light cannot compensate for. In addition, nature has set the biological clock of the human body to rest at night. In sum, this dulls the vigilance of the driver by an average of five times. Dawn and twilight times are very insidious in this respect.
Adverse weather conditions
Everything that limits visibility on the road - rain, snowfall, fog, dust storm - automatically increases the time required for the driver to react to driving. In this case, poor tire grip with the road surface can instantly bring a harmless situation to a threatening one.
Alcohol
Powerful driver reaction time brake - from a twofold increase and more. Even in small doses. This is enough to commit a crime. For no one has canceled the fact that a drunk person driving is a criminal.
Mobile phone
The same unconditional evil for the driver, like alcohol, reduces the reaction to the traffic situation at times. Perhaps the law adopted by the State Duma on increasing the fine for talking on the phone while driving will change the situation for the better. Although, perhaps, it should have been done right away, as in the Netherlands: they are punished with a two-week prison sentence or a fine of 2,000 euros.
Medical preparations
There is an impressive list of drugs, after taking which driving is contraindicated. (And this should be reflected in the information attached to the drug.) Even seemingly harmless cold remedies and painkillers can significantly stretch the driver's reaction time. Not to mention psychotropic drugs. But stimulants are no less dangerous: after taking them, temporary excessive excitement is replaced by a sharp decline. In addition, if the driver feels unwell, is it worth driving in such a state at all? Fatigue
Another factor under the influence of which it is extremely undesirable to hit the road. For example, physical work (many drivers also have to work as loaders) can increase reaction time by 0.1 s. Another variant of fatigue is very often recorded in the accident reports - “fell asleep at the wheel”. Long-distance drivers should take into account that continuous 16-hour work increases the response by 0.4 seconds. Tachographs are designed to solve this problem, monitoring the rest and work time of drivers.
Workplace
The better its ergonomics, the better the driver reacts to the traffic situation. A driver's seat, a ventilated cabin, and the absence of distracting objects are the components of a trouble-free ride. If the transport is freight, reliable fastening of the load, which excludes extraneous noise on the road, also contributes to low driver fatigue. Music
A range of musical pieces that create a favorable, working atmosphere in the cabin, support increased attention and reduce fatigue. However, this applies mainly to intercity routes; in the city, music is more of a distraction. And one more thing: the louder the music, the worse the indicator of the driver's reaction time.
Fragrances
Their action is similar to music. Some scents are relaxing, some are invigorating. Properly selected smell will contribute to the concentration of attention on the road.
The profession of a car driver is one of the most common in the world, at the same time one of the most risky. Every day it requires knowledge of all its subtleties, nuances, an idea of how the body reacts to the variability of the road situation, what factors and how control the driver's reaction time. But without all these terms, neither true mastery nor driving on the roads of the 21st century without mistakes and emergencies is inconceivable.
Time driver reactions is one of the main characteristics that determine the level of traffic safety.
In most cases, it is the speed and correctness of decision-making in the event of a threat of an emergency, as well as the time for their implementation, that directly affect the likelihood of an accident.
Numerous studies have found that the average driver reaction time fluctuates in the range of 0.3 - 1.5 s. The time spread of 1.2 s, expressed as a difference in stopping distances, is 20 m (at a speed of 60 km/h and normal dry road surface). It is these 20 m (and in some cases a shorter distance is enough) that can cause an accident. However, it should be noted that the value of the reaction is not a constant value for a person. Its final value is influenced by many factors, some of which a person is able to adjust towards improvement, while others are individual characteristics of the body.
The term " reaction time» is defined as the period of time that has elapsed from the onset of the stimulus (emergency situation) until the moment the action is taken to eliminate it. Conventionally, this period of time can be divided into two intervals - sensory and motor. The sensory interval has the value of the time spent on the perception of the current dangerous traffic situation, the selection of the object that creates a danger and the decision to prevent an accident. Motor interval refers to the amount of time it takes to perform driving actions to prevent an accident. In studies, it has been determined that the duration of the motor interval is practically stable in every person.
Among the main factors affecting the duration of the reaction, one can single out the difficulty in making a decision (depending on the degree of atypical emergency), gender, age, driving experience (experience), body condition (healthy, sick, emotionally stressed, tired, etc.), concentration of attention on dangerous factors and individual psychological characteristics of the driver's personality, as well as climatic factors and time of day.
The gender and age of the driver affect the visual-motor reaction. Until the age of 25, it averages 0.17 s for a simple reaction and 1.54 s for a complex reaction, and by the age of 60 it reaches 0.26 s for a simple reaction and 2.04 s for a complex reaction. This difference is due to the fact that a complex reaction is characterized by the choice of the correct solution from a variety of options. It is this indicator that is strongly influenced by driving experience.
Time simple reactions women and men do not differ much, but for a complex reaction, women need an average of 2.82 s, while for men this figure is 1.82 s. Also, a relationship was found between the reaction time and the type of higher nervous activity of the driver. So in choleric people, this indicator is 25–30% lower than in phlegmatic people, but they had more erroneous actions.
A factor such as emotions changes driver reaction time depending on personal characteristics. Thus, in laboratory conditions, the average reaction time of the subjects was 0.5 s, and in real conditions, the reaction time to the unexpected appearance of a pedestrian on a country road was 1 s (“a second of fear”). This is due to the psychological unpreparedness of the driver, expressed through a feeling of confusion and shock. Emotions have the greatest influence on the duration of a complex reaction.
The daily dependence of the reaction time is the result of the predominance of inhibitory processes in the cerebral cortex during the night. So at night reaction time increases by 20 - 25% compared with the optimal observed from 7 am to 1 pm.
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