Influence of reflective angle performance and recognition of reflective materials on traffic safety
Traffic signs are necessary measures to guide and manage safe driving on roads, so the recognition performance of traffic signs is particularly important. The recognition performance of traffic signs refers to the basic performance of road users to get the road management language under all weather conditions. Only by seeing and seeing clearly, can the road management language be delivered to the road users in time and correctly, so that they can make the correct judgment and operation. This requires traffic signs to be well recognized during the day and at night.
With the rapid development of urbanization, the number of urban vehicles is increasing, the number of lanes is increasing and the road is widening. The recognition performance of traffic signs is no longer simply the simple reverse reflection, but it is required to adapt to the development of modern vehicles and roads, that is, to meet the recognition of vehicles in various lanes under the condition of multi-lane. Demand and can meet the recognition needs of various vehicle types for traffic signs. This is mainly reflected in the difference of the incident angle performance of the reflective material and the difference of the viewing angle performance, which is commonly referred to as the large angle incidence and reflection performance.
1. Conspicuity tape Incidence angle
The angle of incidence refers to the angle between the illuminating axis and the reverse reflector axis, that is, the angle between the light on the traffic sign and a straight line perpendicular to the line of the logo, as shown in Figure 1. There are many factors that affect the incidence angle on practical roads.
2. Conditions affecting the incidence angle
(1) The influence of the increase of road width on the recognition of traffic signs.
The lateral position of the vehicle on the road is different. For the fixed position of the traffic sign, the “incident angle” between the light and the vertical line of the sign will be different, which affects the reflection efficiency of the light in the reverse reflection loop.
At the same section of the road, the relative angle on the right side of the road is the largest. The maximum angle of incidence on the left side lane is the largest, as shown in Figure 2.
(2) The influence of the distance and speed of vehicles relative to traffic signs on the recognition of traffic signs.
As the vehicle moves, as a traffic sign that is fixed in front of the vehicle, the angle of the incident angle increases with the reduction of the distance between the vehicle and the sign, as shown in Figure 3.
The speed of traffic signs is mainly influenced by the faster the speed of the traffic. The longer the driving distance is, the more the speed and the reading time cannot be changed. Generally, the recognition distance is increased by increasing the font.
(3) The influence of Road flat curve
When the car runs on the road, the incidence angle is affected by the turn. The angle of incidence is smaller before entering the bend, and the angle of incidence becomes larger as it approaches the mark. Figure 4 shows the two change processes of the incident angle in the bend, taking the left side lamp as an example.
As the reverse reflection efficiency is closely related to the incident angle, the smaller the angle of the incident angle is, the higher the reverse reflection efficiency is, the greater the incident angle, the lower the reverse reflection efficiency. Fig. 5 is a comparison between the reflective film with no large angle at different incident angles and the reflective film with large angle performance.
3. Observation angle and safety
The angle of observation is the angle between the incident light and the reflected light. These two rays are a slanting line relative to the cross section of the road, and the angle of the left and right lights is different, as shown in Figure 6. So how to calculate the observation angle has been perplexing the traffic engineering technicians.
In practice, it is more commonly used to calculate the length of 3 lines, such as BA, CA, and eye to light (AB), and then calculate the angle of observation according to the cosine theorem.
First, in the three view, 3 known quantities in the direction of coordinates are shown (see Fig. 7):
X1- marks the distance to the car lamp;
X2- line of sight to the distance of the lamp;
Y1- marks the distance between the middle of the road and the edge of the road;
Y2- lane width;
Y3- the distance from the observer to the midline of the road, that is, the distance between the driver’s eyes and the axis of the vehicle.
The distance from the Y4- lamp to the middle of the road (that is, the distance from the lamp to the axis).
Z1- headlight height;
Z2- line of sight (the driver’s eyes to the ground distance);
The Z3- marks the middle point from the ground height.
According to Pythagorean Theorem, the formula for finding the three line segments is listed.
AB=√(X2)²+(Y4-Y3)²+(Z2-Z1)²
AC=√(X1+X2)²+(Y1+Y2/2+Y3)²+(Z3-Z2)²
BC=√(X1)²+(Y1+Y2/2+Y4) ²+(Z3-Z1) ²
Then according to the cosine theorem: the observation angle takes the car as an example, the above-known quantities are:
X1 =120 m, X2=2.14 m;
Y1 =5.49 m, Y2=3.66 m, Y3=0.35 m, Y4=0.56 m;
Z4=0.62 m, Z2=1.11 m, Z3=2.44 m;
The above data can be taken into the formula to obtain an observation angle of d=0.271 5 degrees.
The data related to the vehicle are replaced by the data of the large vehicle:
X2=2.08 m, Y3=O.42 m, Y4=O.65m, Z1 =0.83m, Z2=1.42 m,
The observation angle of a large car can be obtained at alpha =0.7214.
The relationship between the observation angle and distance of the three vehicles in different sight ranges is shown in Table 1.
From the data in Table 1, it can be seen that the size of the observation angle is mainly reflected in the different types of vehicles. The difference of the observation angle between the different vehicles in the same position when observing the same symbol can reach 100%, the closer the distance is, the more obvious. At the same position of 100 m, the observation angle of the car is less than 0.5 degrees, but the observation angle of the big car is close to 1 degree. At this time, the brightness of the signs seen by the two cars is different, that is to say, the recognition of the traffic signs in the same position is different.
Figures 8 and 9 compare the visibility of different vehicles in the same location.
The sign that the cart sees is dark, which may lead to a driver who can’t see the mark at the distance of the 100 m observation. It can only begin to read the sign from a closer position, so that the driver can’t complete the recognition within the distance of 100 m, and the driver will slow down or even stop to read the sign, which leads to the danger. If you want to make the car more easy to see the sign, there are two ways to make the big car start the observation sign outside the recognition distance. It needs to increase the size of the logo and the brightness of the sign; second is to let the big car see the sign in the view of the big angle, that is to increase the brightness of the sign under the observation angle, that is, Use the brighter reflective products under the Grand View corner. Fig. 10 and FIG. 11 are the curves of the reflection coefficient of two different reflective films along the observation angle.
As can be seen from Fig. 10, the brightness of reflective sheeting with large angle performance is always more than two times that of the reflective film without large angle performance. The brightness of the large angle retro reflective sheet even reached 6 times that of the ordinary reflective film when the best recognition distance of the logo was achieved. This is enough to ensure that large vehicles can see signs clearly and reduce traffic risks in the key visual distance.
Figure 11 shows the relationship between the brightness ratio of two reflective films and the incidence angle. The large angle reflective film can ensure that the vehicle can provide the driver with the brightness of 2 times higher than that provided by the ordinary reflective film, regardless of the incident angle of the vehicle in the bend or the multi-lane road. Order and safety.
4 Conspicuity tape conclusion
In order to ensure the safety of vehicles, more consideration should be given to the reflective materials with large angle performance, especially on the freeway, in order to ensure the safety of the vehicles, in combination with the characteristics of the incident angle and the observation angle mentioned above. We should pay more attention to the problem of first-class highway and urban expressway. In order to improve the driver’s recognition ability for traffic signs, get the road instructions and management information quickly and quickly, reduce the safety accidents caused by the lack of traffic indication information and management information, and make the traffic signs an effective guarantee for the road traffic safety.
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