Automotive Movement safety at night when using front lights

1. The thesis studies the impact of front lights (high and low beam) on safe speed of vehicles at night. When vehicles are running at night, a lighting area created by front lights is an important information source that helps drivers to estimate traffic situations and have right decision when incident occurred. When drivers brake to avoid collision, the information provided by front lights has direct impact on the reaction time of drivers and then braking distance. In this situation, the movement of vehicles will be safe if vehicles are stopped before having collision with objects. This view is the theoretical basis of the thesis and have been announced in the scientific research “Studying the relationship between front lights and movement safety of vehicles”[3]. 2. A formula is developed calculating safe speed of vehicles according to braking distance that is impacted by the driver visibility of object when using only front lights. By the formula, in order to visualize easily for each type of vehicle, a graph is created showing the relationship between driver visibility of object on road and safe speed of each type of vehicles. The testing results point out that safe speed of the 1 st tested vehicle is 59,6 km/h and 2 nd one is 64,3 km/h in the same environment condition. When speeding up to 80 km/h, vehicles will be in unsafe condition because they are only stopped after passing the object. The results have been announced in these studies [4], [6].

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1 INTRODUCTION Nowadays, cars are becoming a popular means of transport in the society, which contributes to create a solid basis for the human progress and civilization. However, apart from the huge benefits cars also cause considerable problems for human people’s life. Annually, there are about over five million victims of severe traffic accidents in the world. According to reports of many countries, economical losses aused by road traffic accidents have achieved 1% to 2% of annual GDP. Obviously, where and when there are people participating in traffic, there is danger of traffic accidents. Thus, traffic accidents have become a burning issue in societies. Vietnam is one of the countries having the highest mortality due to traffic accidents above the total number of transport means in the world. Particularly, in the recent years there has been a sharp increase of the total number of traffic accidents as the result of the rising number of transport means and traffic flows. This trend still has no sign of reduce. On that basis, the implementation of the thesis topic “Automotive Movement safety at night when using front lights” remains its necessity, which has important scientific and practical meaning. Goal: On the basis of studying drivers’ visibility in the condition of using the front lights and the brake capacity of automotive, this paper aims to calculate the safety speed of automotive in that lighting condition. Experiments are needed to verify the results of theoretical calculation. Scope of study - Types of Transport means: Cars and trucks are in line with technical standards and regulation of Vietnam - Operating Conditions: Cars operated in night; front lights used; no street lights at the work road; drivers conduct brake when recognizing pedestrians crossing the road in order to prevent accidents Study method: There is a combination of theoretical and empirical research. Scientific contribution - The thesis studies a new issue in Vietnam from both the theoretical and empirical aspects: Develop an assessment method for movement safety of cars at night when the front lights are used. - The thesis studies the theory of drivers’ vision and factors affecting the drivers’ vision. This paper studies the car front light with the aim of providing information for drivers in the relation of road – cars – environment in order to operating cars safely. On that basis, a method of measuring the vision of 2 drivers for the objects on road in the condition of front lights operated will be developed. - The thesis applies the knowledge of optical physics, automotive theory and specialized materials to access the movement safety of cars at night when the front lights are operated. - The thesis identifies the development of car front light generations which ensures the vision of the drivers and anti – glare capacity for vehicles from the opposite direction. Practical contributions - The outcomes of the thesis may contribute to improve the awareness of the sectoral management specialists and traffic participants about the roles of the car front lights toward the road safety enhancement. - The thesis proposes to complete the technical regulations of car front lights and recommend the safe velocity of cars in relation with the brake capacity and drivers’ vision - The technical concepts, disciplinary and interdisciplinary terminologies of the Drivers – Cars – Road (Environment) system are systematized in accordance with the research purposes. The thesis can be used as referance materials for trainings, scientific studies and development of technical regulations related to movement safety of cars. New contributions of the thesis - This is the first time that the issue of automotive movement safety in relation with the lighting capacity of the front lights has been both theoretically and empirically studied. - The empirical research has been implemented by using modern equipments in the specific conditions of cars, drivers, roads and weather in Vietnam CHAPTER I: OVERVIEW OF THE RESEARCH TOPIC In this chapter, the thesis studies and analyzes the real situation of road traffic safety, concepts about traffic safety and traffic accidents. On the basis, the paper identifies the research purposes, analyzes and access other research related to movement safety and front lights of cars. The goal of the research is to study the movement safety of cars, safe velocity of cars at night. On that basis, the thesis proposes some solutions to minimize traffic accidents at nights. Thus, the thesis mentions a burning issue of the today society. The evaluation of automotive movement safety at night needs to be implemented in specific conditions of environment. The selection of traffic situation should be typical and consistent with the fact in order to ensure the feasibility and reliability when experiments are conducted. 3 Content of the study: - There is study about the drivers’ version for objects on road and method to measure version for objects at nights when car front lights are operated in different conditions. - There is empirical study to measure some relevant parameters such as traction coefficient of the tested road, the efficiency coefficients of tested vehicle’s braking system. - Based on the identification of driver visibility in the condition of using front lights, brake capacity and related parameter, the calculation of car safe speed in that lighting condition is conducted. - The experimental and theoretical calculation results lays a scientific foundation to develop proposals for management agencies in improving quality of car front lights and recommend safe speed of cars in consistence with the street light conditions. Limitation of the research: - The research just focuses on the assessment of automotive movement in the linear motion mode but has not yet considered the unsafety when cars deviate from the brake lines. - The experiments have been carried out only with the tesed cars which are equipped with lighting systems in accordance with the National regulation. - The experiments to access movement safety have been carried out in the limited conditions of some affecting parameters, such as glare source for drivers, rain or fog, slippery or wet road, rough road, mobile objects and so on. CHAPTER II: SCIENTIFIC BASIS FOR CAR SAFETY SPEED AT NIGHT WHEN USING FRONT LIGHTS 2.1. Study of impact factors Factors affecting the automotive movement safety at night when using front lights can be classified into three groups as follows: - The group of factors influenting directly the visibility and control. - The group of factors related to the structure of the means. - The group of environment factors. 2.2. Human eyes and sight Eyes are light sense organs with an extremely sophisticated structure. In daily light, the maximum spectral sensitivity of eyes lies in the yellow-green range at 555 nm. At night, eyes are sensitive to the green with the wavelength of 510 nm. The efficiency curve for night- time light sensitivity of the vision V’(λ) deviates to the left of the daily light sensitivity of the vision about 50nm. 4 Figure 2.4: Line V(λ) day và V’(λ) night of eyes 2.2.2. Some optical features Eyesight Eyesight is determined by the angle at which observers can distinguish between two points or two lines placed closely. The bigger objects are the easier they are recorgnized; there is a relationship between the size d of objects and the seeing distance D and they are associated with the illuminance. Eye adaptation When lighting condition is changed, eyes cannot adapt immediately. It takes a little time or maybe long time to adapt with it. If moving suddently from light to dark places and vice versa, eye cannot adapt, in the first few seconds, eye nearly see nothing. Constrast There are three types of constrast: luminosity contrast, image constrast and color constrast. The phenomenon of glare When there is a significant ratio of luminance, especially in the vision of human eyes, the phenomenon of glare is inevitable making vision comfort be reduced. 2.3. The light color Colors and light are not homogenous concepts. In nature colors are divided into 2 groups: visible light color, invisible light color. When sensing light, human has the psychologically impact of light color according to “imagination” and sense of hot or cold. There are three types of light sources: hot light, neutral light (white) and cold light. 2.4. Front lights The requirements of the optical properties of a light beam 5 According to regulations, it is better to control both areas that are lighted ensuring driver visibility and areas in which light is limited avoiding the phenomenon of glare for drivers in the opposite direction Figure 2.11: Standard Measuring Screen TCVN 6902:2001; 6974:2001;7223:2002 và 7224:2002 The relationship among measurement points and technical requirements According to the theory of lights and the result of test, the detail requirements of light beam when testing in the measuring screen. in this case, points and the control areas of light intensity are selected based on the basis of points and vision areas that have special requirements in order to control the capacity of lighting and reduce the luminance of lights. Vùng 3 Vùng 4 Vùng 1 1 8 7 6 5 4 32 B50L 50V 50L 50R 75L 75R 25L 25R 50 50 BP BP Figure 2.13: The point measuring low beam according to TCVN 6902:2001; TCVN 6974:2001; TCVN 7223:2002; TCVN 7224:2002. 2.5. Street Lighting for vehicles The quality standard of street lighting must to create perceptual view that is fast, correct and comfort. The general requirements are to ensure the function of positioning, navigating vehicles in traffic. The main parameters must be controlled including: Vï ng III Vï ng IV Vï ng I 1500 2250 3960 h 75L 3 7 5 2 5 0 25L 50L B50L 2 5 0 Vï ng II h75R 2 5 0 500 750 2250 7 5 0 V 50V 50R 25R 4 5 ° 3960 1 5 °H1 H H2 V H3 H4 H×nh 2.21: Mµn ®o theo tiª u chuÈn TCVN 6902:2001; 6974:2001; 7223:2002 vµ 7224:2002 Vùng III ù g IV ùng II Vùng I 6 The average luminance of road surface plays a more important role than the luminance because in order to distinguish an object from a long distance at night, the lighted road surface will become a secondary lighting source and when the regulated luminance must be reached, it can distinguish objects on road from the night 2.6. The factors related to drivers - Drving skills and habits of drivers in traffic - The health of drivers, regular driving time - The age effect of drivers - The driver visibility when using the front lights 2.7. The factors related to vehicles Front Windshield: is a component that has direct impact on the safety of drivers and vehicles. The component must be checked the quality and the safety before mounting. The physical feature of front windshield has direct impact on the visibility of drivers including: light transmission, distortion, Secondary image separation, the change in color. Braking system in automotive: the quality of braking system in cars plays a important role ensuring automotive movement safety. The nature of assessing automotive movement safety when using front lights will assess the capacity of automotive brake when detecting objects in the condition of using only front lights. 2.8. Factors related to motorways Some techinical regulations in the standard motorways have direct and in direct impact on the driver visibility as well as the automotive movement safety: designed speed, the minimum width of a lane, hozirontal slope, vision, radius of curvature, ultra-high slope, longitudinal slope, flatness 2.9. Factors related to speed and distance between vehicles in traffic When movement speed is increased, the visibility of drivers is reduced. In fact, driver visibility reduced is due to observation angle narrowed; near objects move with high speed so human eyes cannot distinguish. Figure 2.21: The relationship between speed and drivers’ angle observation 7 In road traffic, the regulations of speed and distance between vehicles must be obeyed. 2.10. Weather factors Fog and Rain The visibility limitation of drivers in the weather of fog and rain depends mainly on the rainfall or the thickness of fog as well as the level of lighting. In addition, there are other factors limiting the driver's visibility and affecting automotive movement safety such as: slippery road surface, uneven road surfaces, moon light 2.11. Chapter II Conclusion - Selecting observers in the test of measuring and assessing safety should consider the issues of eyesight, other eyes problems, ages, health, driving skills... - Selecting tested vehicles should consider types of vehilces meeting current techinical regulation and standards, and using front lights that are popular and meet Vietnamese standards. - When developing modelling, the testing procedure must be based on the type of vehicles, front lights mounting on the selected vehicles, the standards of lights, vehilces, light color, tested objects, the position of the objects. - Selecting the place to conduct the test must consider the factor of weather; removing secondary lighting sources, glare source, the good quality of road surface; the weather factor must ensure not to affect or change the measuring results. CHƯƠNG III. BUIDING AND TESTING THE MODELLING OF ASSESSING OF AUTOMOTIVE MOVEMENT SAFETY AT NIGHT WHEN USING FRONT LIGHTS 3.1. The relationship between driver – vehicles - weather The movement of cars is a result of the frequently interactive process between the objects of Driver - Car - Environment system in a space and time Figure3.1: The information system of Driver - Vehicle – Environment) (ĐK - The control circuit; LHN – Reversed contact circuit) Road - Environment Vehicle Driver LHN 2 LHN 1 LHN 3 ĐK 1 ĐK 2 X 8 The activities of the driver are based on information received. In fact, sometimes the information is wrong due to situations on the road constantly change. So, drivers themselves should be able to forecast, inference, to prevent these. To study about movement safety, automotive is considered as a system tightly associated with drivers and road (environment). In each specific operating condition, these factors have direct impact on and dominate each other as well as being causes of accident. Therefore, to study movement safety of cars at night using front lights, we will examine the relationship among Drivers – Cars – Environment based on analysing potentially unsafe factors caused by the three above subjects in the night condition and using front lights. 3.2. The types of traffic collistions and the selected study model To build experiment model, we should exemmine and assess the types of collision when road traffic accidents occur. There are 9 types of collisions. When a driver is driving a car, the driver often forcuses on following objects including pedestrians, bikes, motorbikes, cars in the same and opposite lanes (40-60%), the motorway ( 5-25 %); looking traffic situation around (25-35 %). Among them, the most difficulty is to detect pedestrians due to their characteristics: the size (small), color (easily confused with the environment), noise (no), irregular movement (can change very quickly from standing to moving, from walking to running, from forward to backward , go straight to turn left or to the right...). Therefore, the 1 st type of collision: car accidents with pedestrians are selected to conduct the study of movement safety. 3.3. Building a method of assessing automotive movement safety 3.3.1 The working of Car Brake System With the assumptions of selected study model, the assessment of movement safety will be proceeded through the assessment of the brake quality. In principle, the assessment of the brake quality is based on the indicators of brake effectiveness and direction stability of a car during braking. In the scope of this thesis, with the assumption is that collision will not occur and the cars will stop before an object, so when the assessment of braking process will not consider the indicators direction stability of a car during braking. Meanwhile, the assessment of movement safety will be conducted through the assessment of braking distance indicators. Dynamic Braking In braking process on road, the forces and monents impacting on vehicles braking will cause a major influence in the vertical plane (ZOX), horizontal plane (Zoy). In the horizontal plane, the vehicles’ orbits are deflected away 9 from the movement at an angle β. So we have the differential equations determining the dynamics of the vehicles braking by the main brake system.    x T2PFPTPFPx v G )PPPP(g dt dv 211 x p v dt dS       y F2T2F1T1y v G )YY()YY(g dt dv (3.4) y y v dt dS    Gab b)YY(a)YY(g )PPPP( Gab2 Bg dt d T2F2T1F1 TPFPTPFP 2211      dt d Solving the the differential equations (3.4) is to define the assessment criteria of brake nature. Braking distance and brake time To determine the actual braking distance, it is necessary to exemine the brake process through the experimental graphs showing the relationship between the braking force generated at wheels (or braking moment) and brake time. This graph is called brake schema (is the relations of brake force Pp (the accelerator j and time t) as in Figure 3.17 Hình 3.11: Giản đồ phanh Figure 3.17: Brake schema t Pp , j A B t1 t2 t3 t4 t5 0 10 If counting the reaction time of the driver (t1), the delay action time of t2 braking system, the actual brake distance will be calculated as follow: g2 K.v TS p 2    (3.7) 3.3.2. The visibility of drivers at night when using front lights Basing on the facts above, there is not a specific formula to calculate the visibility of objects on the road at night using front lights. Thus, theoretical studies mainly focus on the exemination of the impaired visibility of drivers due to particular impact factors. However, experimentally, we totally identify the visibility of objects at night using front lights in specific lighting conditions. 3.3.3. Safe spead in the condition of visibility limitation The main cause of road traffic accidents are due to driver selecting incorrect speed. To ensure movement safety with optimum speed, the driver must to maintain the ability to observe road in conditions that are corresponding to the vehicle operation modes, especially selected speed should be corresponding to the conditions of high visibility and objects on road. According to the view of driver visibility, conditions for movement safety is a distance that objects on the road can be detected must be greater than or equal to a safe distance when braking. On that point, we have the formula determining a safe distance based on the ability of vehicle brake as followsss: 0 p 2 0pnt S g2 Kv vTSSS     (3.11) Based on the 3.11 formula, we can create a graph of the relationship between car speed and distance S0 that is calculated from the point a car stops to objects on the road. Suppose, a type of car has brake efficiency Kp = 1,1; The adhesion coefficient of road surface is chosen as 0.7, the total time to recognize objects on the road, the driver's reaction and delay action time of the brake system TΣ = 1,2seconds; visibility Snt is 46.5 m, g = 9.8 m/s 2 . So we have a graph showing the relationship between car speed and the distance of S0 as shown in Figure 3:19 11 Hình 3.19: The relationship between cars speed and the distance of S0 Based on the formula 3.11, we can define safe speed of cars in the condition of limited visibility as followss:                   0nt p2 p at SS K 2,0TT K g v (3.12) Thus, according to the formula 3.12, to each type of cars, we can create a graph of relationship between the driver visibility and safe speed that is corresponding to the braking capability of the vehicle. Suppose, a type of cars has brake efficiency coefficient Kp = 1.1; the adhesion coefficient being corresponding changes of 0.3, 0.5 and 0.7, the total time to recognize objects on the road, the driver's reaction and the delay action time of the brake system TΣ = 1,2seconds; the distance from the point the car stops and the object is S0 = 5m g = 9.8 m/s 2 . So we have a graph showing the relationship between the driver visibility and safe speed as shown in Figure 3:20 Figure 3.20: The relationship between safe speed and driver visibility 115.91 124.2 78.45 85.85 92.72 99.1699.87 86.41 71.12 52.96 29.19 112.04 123.22 133.62 143.39 152.63 107.08 97.58 26.61 132.04 87.24 75.78 62.74 47.18 105.25 70.4 61.45 22.7 39.03 51.25 0 20 40 60 80 100 120 140 160 180 0 20 40 60 80 100 120 140 160 180 200 Tầm nhìn Snt (m) V ậ n t ố c a n t o à n V a t (k m /h )  =0.7  =0.5  =0.3 S0 Sp 12 3.3.4. The method of assessing automotive movement safety at night To assess automotive movement safety basing on the safe distance being corresponding to the capacity of brake p nt atp S S K  (3.13) We can assess movement safety of vehicles basing on following formula: v v K at atv  (3.15) If the efficiency of lighting equipment is considered as the highest safe speed of vehicles at night, thus we can define the assessment criteria of safe coefficient of fron lights as followss: - Low beam: c cc c v v K  (3.16) - High beam: p c p v v K  (3.17) - the general safe coefficient of front lights is the product of Kc and Kp, which means: p cc p c c cc atd v v v v v v K  (3.18) The physical meaning of the above equation can be interpreted as follow: when Katd is smaller, which means that the highest safe speed while avoiding cars in the opposite lane is smaller compared with the highest one of using hight beam and therefore it should brake as quick as possible in order to reduce the current speed to safe one. So, in theory, the closer to 1 the safe coefficient Katd is, the more perfect the front lights system is 3.4. Chapter III Conclusion - According to the scope of the study of movement safety, suppose the car stops before the collision occurs, so the calculation of the safe speed of vehicles by comparing driver visibility of objects on road and the capacity of brake is proper. - For each type of cars, based on the formula of safe speed, we can create the graph of the relationship between driver visibility and the safe speed of the type of cars in different traffic conditions. 13 - Safe coefficient Katd can characterize for one lighting system and be different from others. However, to select an optimal lighting system, the specific use condition of different types of car should be considered CHƯƠNG IV. EXPERIMENTAL STUDY 4.1. Identifying the purpose and content of the experiment In the scope of thesis, the experiment will focus on the following main purposes: - Developing and completing the measurement of visibility of the object on the road in terms of using front lighting; - Carrying out measure, determining input parameters to calculate the theoretical safe speed being corresponding to front lighting system equipped on cars. - Develop the study method of assessing movement safety of vehicles at night when using front lights - Through the study method of assessing movement safety of vehicles at night when using front lights, the results of previous theoretical calculations will be checked 4.1.2. Content of the test The content of the experiment will be divided into two main parts: Part 1: Testing, determining input parameter to calculate the theoretical safe speed of vehicles. Part 2: Testing, assessing movement safety of vehicles on road when driving at theoretical safe speed and at limited speed in traffic. 4.2. Testing 4.2.1. Test of measuring of driver visibility The testing modelling is built based on the modeling of accident diagram between pedestrians and a car. There are two testing modelkings measuring different visibility that are corresponding to the use of high and low beam. Người qua đường Người qua đường bên trái bên phải 35 30 25 20 15 10 5 0 35 30 25 20 15 10 5 0 Người qua đường Người qua đường bên trái bên phải 35 30 25 20 15 10 5 0 35 30 25 20 15 10 5 0 Figure 4.1 và 4.2: Modellings measuring visibility when using high and low beam. 14 The testing results of visibility measurement Table 4.1: The results of Modelling 1 (a car) Observed object Low beam High beam Object standing on the right Object standing on the left Object standing on the center distance (m) Illumi nance (lux) distance (m) Illumi nance (lux) distance (m) Illumi nance (lux) Dark blue 49,8 0,8 38,8 0,8 156,7 2,3 Dark red 54,7 0,8 46,5 0,6 165,8 2,2 White 62,7 0,7 54,5 0,5 232,6 1,5 Table 4.2: The results of Modelling 2 (a truck) Observed object Low beam High beam Object standing on the right Object standing on the left Object standing on the center distance (m) Illumi nance (lux) distance (m) Illumin ance (lux) distance (m) Illumina nce (lux) Dark blue 61,3 1,5 53,8 1,2 211,2 2,2 Dark red 69,1 1,7 55 1,1 236,7 2,0 White 73,6 1,3 62 0,7 273 1,4 4.2.2. The testing of measuring the coefficient of traction of tested road The purpose of the test is to identify the coefficient of traction of tested road. The coefficient of traction of tested road will be identified by testing of brake on road. The braking force created at the wheels will be defined as following formula Pp = φG, therefore it leads to: p 2 gS2 v  (4.2) Devices used in the test of measuring of brake distance - Devices measuring Brake Distance and Speed Figure 4.8 và 4.9: Brake Distance and Speed check Devices 15 Some pictures about the test of measuring of brake distance Using the formula 4.2 to calculate the value of corresponding φi. Processing the same data of 4.2.1.8, we have the result of the coefficient of traction of tested road as Table 4.3 Table 4.3: The result of the coefficient of traction of tested road Expectation Variance Conclusion the coefficient of traction 0,68 0,08 0,68 4.2.3. The test of measuring coefficient of brake efficiency coefficient of brake efficiency will be calculated as follows: ptt p p J J K max  (4.4) Jpmax - brake acceleration (in theory) is calculated by the above formula; Jptt - brake acceleration (by measuring tested cars) The tested cars are the ones used in the test of driver visibility. - The 1 st one: a car Type: KIA Sorento - The 2 nd one: a truck Type: CỬU LONG Figure 4.14: Tested vehicles 16 The results of brake acceleration measuring test Jptt Figure 4.4: The results of brake acceleration test Jptt Brake acceleration Jptt 1 st tested vehicle KIA SORENTO 2 nd tested vehicle CỬU LONG Expectation 6,49 5,87 Variance 0,11 0,13 Conclusion 6,49 5,87 The results of calculating the coefficient of brake efficiency based on maximum slower acceleration when braking (Formula 4.4) is shown as following table 4.5: Figure 4.5: The results of calculating the coefficient of brake efficiency 1 st tested vehicle KIA SORENTO 2 nd tested vehicle CỬU LONG The coefficient of brake efficiency Kp 1,02 1,15 4.2.4. The test of assessing movement safety of cars According to the results of measuring the driver visibility of objects on road at night when using front lights Snt, the results of measuring the coefficient of brake efficiency Kp, the coefficient of traction of tested road  , the safe speed of tested vehicles will be calculated. The relationship between the visible distance of objects and the safe speed of vehicles is shown in Graph 4.17 and 4.18 The curves in the graphs show safe limitation, the areas under the curves are safe ones, and the areas above the curves are dangerous ones. Figure 4.17: The relationship between safe speed of 1 st tested vehicle (KIA SORENTO) and the visible distance 17 So, for the 1 st tested vehicle KIA SORENTO, when driving at night and using low beam (the driver visibility is 46,5m - red object on the left), safe speed calculated is 59,6 km/h. In case of the object on the left but in dark blue, the driver visibility is reduced to 38,8m and then the safe speed calculated is down to 51,8km/h. Figure 4.18: The relationship between the safe speed of the 2 nd tested vehicle (CỬU LONG) and the visible distance For the 2 nd tested vehicle Cửu Long, when driving at night and using low beam (the driver visibility is 55m - red object on the left), then safe speed calculated is 64, 3 km/h. In case of the object on the left but in dark blue, the driver visibility is reduced to 53,8m and then the safe speed calculated is down to 63,3km/h. 4.2.4.1. Building an experimental model According to the modeling of accident between pedestrians and a car, selecting the case of a pedestrian appearing at the left pavement, and the car using low beam (this is the most dangerous according to the view of driver limited visibility), the modeling of assessing movement safety of cars as shown as Figure 4.19 18 Người qua đường Người qua đường bên trái bên phải 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 35 Figure 4.19: the modeling of assessing movement safety 4.2.4.2. The observed object used in the test In the test, the observed object selected is a dark red paper board (reflectance 0,3 size 1,7m x 0,33m) Figure 4.20: The observed object used in the test. The object is located at the left pavement 4.2.4.3. Lighting Conditions In order to the consistency with the results of theoretical calculations, lighting conditions and environment in the test of movement safety will be similar to those of the test of driver visibility. Therefore, the test of movement safety will be conducted right after the test of driver visibility. Besides, the test is only conducted in case of using front lights. 19 4.2.4.4. Tested vehicles The tested cars are the very ones used in the test of driver visibility - The 1 st one: a car Type: KIA Sorento - The 2 nd one: a truck Type: CỬU LONG 4.2.4.5. Tested drivers The driving tested vehicles accoding to the testing procedure is very important. Therefore, the register officers of the Department of Register were seleted to drive tested vehicles, the visibility is 10/10 and no eyes problem. 4.2.4.6. Devices used in the test - Brake Distance Check Device + Branding: Circuitling Brake Check; + Model: BRK 05985 - Series 2; + Made in: Australia; + Variance: 1%; - Speed Check Device + Brand: GARMIN GPS72; + Model: 13434208; + Made in: TAIWAN; + Check range: 0 - 300 km/h; + Variance: 1%; - Distance meter device - Wireless handheld radio. 4.2.4.7. The procedure and test results of assessing movement safety of vehicles The preparation of tested vehicles and the testing procedure are similar with those of the test of measuring brake distance. Testing Procedure Vehicles will be tested in idle mode and tires are pumped following the manufacturer’s pressure standard; equipment and accessories are installed, fuel is filled at least 2/3 of the tank. The speed of the tested vehicles (the speed at when starting braking) - The Car: 59,6 km/h - as the above calculation - The Truck: 64,3 km/h - as the above calculation Measuring Procedure: + Step 1: Installing of the measuring devices in the vehicles and checking the status of the device. + Step 2: Starting and driving the vehicles to the starting position + Step 3: Starting the vehicles following the procedure, speed up to tested speed and keep it. When recorgnizing the object on the road, the driver quickly brakes (for vehicles using manual transmission, the driver kicks simultaneously 20 clutch pedal and brake pedal), keeps kicking brake pedal until the vehicles stop. + Step 4: Read and record the values displayed on the measuring devices, such as the speed at the time of starting braking, braking distance. Measuring remaining distance is from the vehicle to the observed object. Noting the results on the form provided in Appendix 4. Carrying out the measuring 20 times following the procedure There are some pictures of the test of assessing movement safety of vehicles Figure 4.21: the test of assessing movement safety of vehicles The testing results of assessing movement safety of vehicles The result of each measurement is shown in Appendix 4 - Table 4.1, Table 4.2 The data processing of the test is similar to 4.2.1.8, the result of assessing movement safety of vehicles is shown as the table 4.6 Table 4.6: the results of assessing movement safety of vehicles 1 st tested vehicle KIA SORENTO 2 nd tested vehicle CỬU LONG Sp (m) S0 (m) Sp (m) S0 (m) Expectation 20,85 6,28 24,83 5,88 Variance 0,77 0,89 0,67 0,72 Conclusion 20,85 6,28 24,83 5,88 21 Figure 4.22: the results of assessing movement safety of vehicles - The tested vehicle CỬU LONG Comments: - In all the testing, the vehicles stopped before the observed objects, have no collision. The remaining distances from the head of vehicle to the object for the 1 st ans 2 nd tested vehicles are 6,28m and 5,88m respectively - The testing results are fairly appropriate to the theoretical calculation (Assumption: the vehicle stopping is 5 m in front of the object) 4.2.5. The test of assessing movement safety at the speed of 80 km/h The limited speed 80km/h is regulated for most roads, roads that are in suburbs and resident areas. When driving in these roads, drivers are allowed to speed up to 80km/h and use both high and low beam at night. The test results of assessing movement safety of vehicles The result of each measurement is shown as Appendix 5 – Table 5.1 The data processing of the test is similar to 4.2.1.8, the result of assessing movement safety of vehicles is shown as the table 4.7 Table 4.7: : the results of assessing movement safety of vehicles at the speed of 80 km/h. 1 st test vehicle KIA SORENTO Sp (m) S0 (m) Expextation 32,51 - 7,87 * Variance 1,38 0,86 Conclusion 32,51 - 7,87 * Minus sign (-) means the location the vehicle passed the object 65; 5.88 40; 31.8 50; 22.9 -15.95 50.97 45.57 -2.24 38.77 30.6 21.04 10.09 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 0 10 20 30 40 50 60 70 80 Vận tốc thử v (km/h) K h o ản g c ác h g iữ a đ iể m ô t ô d ừ n g v à ch ư ớ n g n g ại v ật S o ( m ) w Giá trị thử nghiệm thực tế (vận tốc thử, khoảng cách giữa điểm dừng và vật cản) Đường lý thuyết 22 Figure 4.23: The results of assessing movement safety of vehicles – The tested vehicle KIA SORENTO Comments: - In all the testing, the vehicle cannot stop before the observed objects; the probability of collision is 100%. The distance of the vehicle passing over the object is 7,87m 4.3. Conclusion Chapter IV - It is necessary to calculate the safe speed of vehicles at night when using front light as well as conducting the test of assessing movement safety of vehicles in order to exemine and provide some solutions addressing car accident. - The test of measuring driver visibility is not too complicated and might be applied in some specific traffic conditions. The testing results point out that driver visibility is reduced to 38,8m in case of using only low beam and the object in dark blue and in the left of the road. - According to the assumption of environment in the test, the safe speed of vehicles is higher than 50km/h when using low beam. So, in theory, the regulation of speed limit in traffic in resident areas that is not over 50km/h is appropriate with the safe condition of vehicle. However, this is correct without dazzlement, fog, rain… - In traffic it will be not safe if vehicles use only low beam to light the front areas with the speed that is near the speed limit 80 km/h (the regulation at suburbs) - Drivers must simultaneously control safe speed and control the safety of the vehicles they drive. Therefore, the manufacturers should provide quantitative warning about safe speed to drivers in case of driving at night and bad weather 40; 25.2 50; 15.9 60; 6.28 80; -7.87-6.65 14.62 23.43 31.02 46.5 4.6 -19.1 42.56 37.4 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45 50 0 10 20 30 40 50 60 70 80 Vận tốc thử v (km/h) K h o ả n g c á c h g iữ a đ iể m ô t ô d ừ n g v à c h ư ớ n g n g ạ i v ậ t S o ( m ) Đường lý thuyết w Giá trị thử nghiệm thực tế (vận tốc thử, khoảng cách giữa điểm dừng và vật cản) 23 CONCLUSION AND RECOMMENDATIONS Road traffic safety in general and movement safety of vehicles at night when using front lights in particularly have been concerned by Vietnamese society. The subject of the thesis has both scientific and practical meaning and is appropriate to the speciality of mechanical dynamics and partly addresses the concern. The main study results of the thesis 1. The thesis studies the impact of front lights (high and low beam) on safe speed of vehicles at night. When vehicles are running at night, a lighting area created by front lights is an important information source that helps drivers to estimate traffic situations and have right decision when incident occurred. When drivers brake to avoid collision, the information provided by front lights has direct impact on the reaction time of drivers and then braking distance. In this situation, the movement of vehicles will be safe if vehicles are stopped before having collision with objects. This view is the theoretical basis of the thesis and have been announced in the scientific research “Studying the relationship between front lights and movement safety of vehicles”[3]. 2. A formula is developed calculating safe speed of vehicles according to braking distance that is impacted by the driver visibility of object when using only front lights. By the formula, in order to visualize easily for each type of vehicle, a graph is created showing the relationship between driver visibility of object on road and safe speed of each type of vehicles. The testing results point out that safe speed of the 1 st tested vehicle is 59,6 km/h and 2 nd one is 64,3 km/h in the same environment condition. When speeding up to 80 km/h, vehicles will be in unsafe condition because they are only stopped after passing the object. The results have been announced in these studies [4], [6]. 3. Some tests were conducted in order to measure driver visibility of object when using front lights, the traction coefficient; analysing and selecting the reaction time of driver when braking at night and using only front lights to be input parameter for calculation. The results of calculation and testing are fairly similar, which shows the accuracy of the modelling. The results have been announced in these studies [5],[6]. 4. Method and devices measuring driver visibility on road used in the thesis can be applied in practice and on the roads where accidents are usually occurred at night. In addition, the maximum speed of vehicle at night on these roads must be regulated [4],[5]. 24 5. The assessment of front lights by safety factor (Katd, Kc, Kp) helps manufacturers and drivers to have a quantitative comparision among types of lights in order to study as well as selecting products. The thesis can be used as a reference for manufacturers producing and assembling vehicle lights, vehicles as well as road traffic safety departments, the training and research institutions Recommendations: - Drivers should control and select speed that is appropriate to visibility. Drivers must be capable of using the high and low beam of vehicles to ensure safe traffic. When driving at night in resident areas with the speed limit ≥ 80km/h, in order to be safe driver should use high beam. If low beam must be used for any reason, drivers should reduce to safe speed. - Car manufacturers should provide drivers with warning about safe speed limit of each type of cars when using low beam and in dangerous case such as visibility reduced suddently.

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