Patent Description:
The middle section of road tunnel is a relatively closed structure, and is not affected by natural light. When the driver is driving in a tunnel middle section, the driver's visual and psychological burden will increase, as compared to when driving in an external environment. In order to improve the visual environment of tunnel, lighting facilities should be used in the tunnel, and a tunnel middle section brightness value which can satisfy the visual information collection requirements as well as the driving safety and comfort requirements of the driver driving a motor vehicle at a certain speed in the tunnel middle section should be provided, that is to say, a safe driving brightness level should be reached by the tunnel middle section.

In recent years, new road lighting lamps are developing quickly, and people more and more deeply focus on tunnel safety. But at present, there mainly exists the following problems: At home and abroad, the illumination standard of the tunnel middle section is made according to the light source of sodium lamp, the evaluation of illumination standards are mostly performed based on the subjective experience of a driver or an expert with qualitative assessment of the brightness of the tunnel middle section. Or it is based on the driver's psychological and physiological indicators to evaluate the safety of the tunnel middle section. There is a lack of research on illumination standards under different light source characteristics in the tunnel middle section that meets the driver's visual recognition requirements in an actual operation process. Study on the characteristics of the lighting source and visual recognition of a small target object in the tunnel middle section usually adopts a static measuring method, and indicators such as the reaction time are used in order to conduct theoretic study, which limits the selection of the characteristic indicators of the light source. So it is needed to find a simple and convenient technique to accurately calculate the illumination standard corresponding to different light source characteristics for a tunnel middle section based on safe visual recognition.

<CIT> relates to an on-site dynamic measurement method of LED road lighting. "<NPL> relates to a comparison of three tunnel lighting systems, namely symmetrical, counter-beam (CBL) and pro-beam (PBL) under the same geometrical and weather conditions. <CIT> relates to a tunnel running lighting sets quality inspection system, mainly used in highway tunnel lighting project, urban lighting and road underpass lighting project and other artificial lighting engineering.

An objective of the invention is to solve the above-mentioned technical defects existing in the prior art, by providing an illumination standard calculation method for a tunnel middle section which is reliable and easy to operate and meets the requirements of the driver's visual perception, and also by providing a system for implementing the illumination standard calculation method for different light source characteristics of a tunnel middle section based on safe visual recognition which is simple and reliable with high utilization rate, so as to overcome the technical defects that the existing illumination standards of the tunnel middle section has unreliable basis and complicated tests with results that do not take into account the driver's psychological and physiological factors.

In order to solve at least one of the above problems, a first aspect of the invention is to provide an illumination standard calculation method for a tunnel middle section based on safe visual recognition according to claim <NUM> of the present application.

A second aspect of the invention provides a system for implementing an illumination standard calculation method for a tunnel middle section based on safe visual recognition according to claim <NUM> of the present application.

In the method and system of the invention, by combining and screening the information related to responsive driving behavior and visual recognition status towards small target object of a driver in the tunnel middle section under different light environments established by illumination devices, comprehensive safe illumination standards for the tunnel middle section that meets the safe visual recognition requirements of the driver are provided, with consideration of the driver's visual perception requirement characteristics from the driver's angle, thereby improving the accuracy of safety evaluation of the tunnel middle section brightness, with easy and convenient operation method, so as to provide a reference basis for the research of road traffic safety.

Referring to the accompanying drawings, more objectives, functions and advantages of the invention will be clarified in the following description of the embodiments of the invention wherein:.

<FIG> shows a flow chart of the method of measuring the minimum brightness value of the tunnel middle section. <FIG> shows a schematic diagram of the dynamic test of the illumination standard calculation method for a tunnel middle section based on safe visual recognition. The invention provides an illumination standard calculation method for a tunnel middle section based on safe visual recognition, which calculates the minimum brightness value of the tunnel middle section that meets the safe visual recognition requirements under different light environments, so as to ensure that the driver's driving safety.

Referring to <FIG> and <FIG>, the illumination standard calculation method for a tunnel middle section based on safe visual recognition provided by the invention comprises the following steps:.

In order to make the illumination standard calculation method of the invention more reliable and conform to the international standard, in the present embodiment of the illumination standard calculation method for the tunnel middle section <NUM> based on safe visual recognition in the present invention, the target object A <NUM> is a gray cube with a volume of <NUM>*<NUM>*<NUM> and a reflectivity of <NUM>%. In order to eliminate the influence of the driver's memory of the target object position on the experimental results, in the tests, the target object position in the tunnel middle section <NUM> is arbitrary.

In order to simplify the illumination standard calculation method for the tunnel middle section <NUM> based on safe visual recognition of the invention, and in order to do measurement quickly, in this embodiment, a non-contact speed meter installed on the motor vehicle <NUM> is utilized. When the driver visually discovers the target object <NUM>, the non-contact speed meter is triggered to record a first position; when this driver reaches the target object <NUM>, a second position is recorded. The distance between the two positions is regarded as the visual recognition distance D. This can quickly measure the visual recognition distance, reduce the time for the implementation of the steps, and increase the efficiency of the implementation of the steps.

In this embodiment of the illumination standard calculation method for the tunnel middle section tunnel based on safe visual recognition of the invention, the brightness value of the tunnel middle section is measured by using a luminance meter or an illuminometer, and when using the illuminometer, it is necessary to calculate the relationship between the average brightness value and the average illumination value of the tunnel middle section, i.e., to calculate the average illumination conversion coefficient, so that the brightness value can be calculated after the illumination value is measured; the color temperature and the color rendering index of the tunnel middle section are measured by a luminance spectrophotometer.

In this embodiment of the illumination standard calculation method for the tunnel middle section based on safe visual recognition of the invention, the step of changing the illumination brightness of the tunnel middle section <NUM> is performed by changing the output power of the illumination device <NUM> in the tunnel middle section <NUM>, without replacing the illumination device <NUM> in the tunnel middle section, thus it is convenient to implement the present embodiment.

In order to make the results more accord with the objective reality, in this embodiment of the illumination standard calculation method for the tunnel middle section based on safe visual recognition of the invention, a number of drivers are randomly selected at different ages, different eyesight levels within the normal range, and different driving experience.

On the basis of Embodiment <NUM>, the invention can calculate minimum brightness values of the tunnel middle section that meets the visual recognition requirements under different light environment and then obtain the safe visual recognition threshold. <FIG> is a flow chart of the method of measuring the safe visual recognition threshold of the tunnel middle section in Embodiment <NUM>; <FIG> is a schematic diagram of the static test of the illumination standard calculation method for the tunnel middle section based on safe visual recognition.

Referring to <FIG> and <FIG>, in this embodiment of the illumination standard calculation method for the tunnel middle section based on safe visual recognition of the invention, on the basis of Embodiment <NUM>, the following steps performed by using a simulation tunnel are also included:.

This embodiment of the present invention applies the method of Embodiment <NUM> to a test in an actual tunnel middle section. A tunnel middle section <NUM> of a highway in a province is selected for measurement of its safe minimum brightness value L. The freeway tunnel total length is <NUM>, the maximum speed limit is <NUM>/h, the light environment of the tunnel middle section has a color temperature of <NUM> and a color rendering index of <NUM>, and the road surface in the tunnel is covered with bituminous concrete. <NUM> motor vehicle drivers are randomly selected as test subjects. The illumination device is arranged to set different average brightness values in the tunnel. The driver is asked to drive a motor vehicle <NUM> at a certain speed from the outside of the tunnel toward the inside of the tunnel and try to visually recognize the front target object <NUM> during the driving process, with a criterion that the driver is able to easily and quickly find the target object <NUM>, and the driver's visual recognition status towards the target object <NUM> is recorded.

In the visual recognition process, the visual recognition information when the driver is driving on the test section and the light environment information of the tunnel middle section are collected. According to the model of the invention, the brightness value of the tunnel middle section is calculated. Under different brightness values of the tunnel middle section, drivers try to visually recognize the target object in the tunnel middle section. A total of <NUM> samples were collected, and the effective samples were <NUM>, as shown in Table <NUM>.

After partial correlation analysis, it is found that the visual recognition distance D has low correlation with the driving speed of the motor vehicle <NUM>, but has high correlation with the brightness L of the tunnel middle section <NUM>. By the S model fitting, the following formula is obtained: <MAT> The safe stopping sight distance D<NUM> corresponding to a color temperature of <NUM> and a color rendering index of <NUM> is substituted into the formula (<NUM>) to calculate the minimum brightness value L<NUM> of the tunnel middle section under such a light environment associated with different maximum speed limits (<NUM>/h, <NUM>/h, <NUM>/h, <NUM>/h). Referring to table <NUM>:.

Based on Embodiment <NUM>, the present embodiment of the invention carries out a static test of the actual simulation tunnel. A simulation tunnel <NUM> is selected to simulate the tunnel middle section, and in this simulation tunnel, the illumination device <NUM> may be selected from a variety of lighting fixtures, making the tunnel light environment parameters such as average brightness, color temperature and color rendering index easier to adjust and measure. The road surface in the simulation tunnel is covered with a series of diffuse reflection materials similar to the material of a bituminous concrete road surface, which is modified asphalt waterproof coiled material.

The color temperature is related to the spectral energy distribution, and the spectral composition is the most important determinant of the color temperature of a light source. The human eye is more accustomed to the natural daytime light spectrum, and through the investigation of spectral composition of the daytime light, it is found that light close to the daytime light has a color temperature distributed in the range of <NUM>-<NUM>. As for the current tunnel illumination device <NUM>, the color temperature of sodium lamp is low, at about <NUM>. By reference to the commonly used color temperature of the existing tunnel lamps provide by the related lighting fixture manufacturers, the color temperature of the illumination device <NUM> in the embodiment is selected to be at five color temperature levels of <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> for testing.

The color rendering index of light source is an important parameter to evaluate the color quality of a light source, which indicates the conformity extent of the color rendered for an object by illumination of the light source and the color rendered by illumination of the standard light source (sunlight). CIE stipulates the color rendering index of sunlight to be <NUM>. In the current tunnel design, the color rendering index of the light source of the lighting fixture is not less than <NUM>. So this experiment selects three color rendering index levels of <NUM>, <NUM>, and <NUM>. By using the <NUM> color temperature levels and <NUM> color rendering index levels for experimental design, a total of <NUM> combinations are tested.

In this embodiment, <NUM> drivers with normal eyesight are randomly selected, the static visual recognition test is carried out, and the static visual recognition minimum brightness values under different light environments are collected, as presented in Table <NUM>.

The static visual recognition minimum brightness value associated with a light environment of (<NUM>, <NUM>) of the tunnel middle section is set as the benchmark to calculate the visual calibration factor a. Then the dynamic visual recognition minimum brightness value, namely L0d, that meets the visual recognition distance requirements under different environments are calculated. Results are shown in Table <NUM>, which are suitable for the free flow traffic condition.

According to the above results, the minimum brightness values L0d corresponding to a particular maximum speed limit under different light environments of the tunnel middle section <NUM> can be designed.

The invention also provides a system for implementing the illumination standard calculation method for a tunnel middle section based on safe visual recognition. The system includes a tunnel middle section subsystem that comprises illumination devices <NUM> with adjustable output power installed in the tunnel middle section <NUM> for setting the light environment; a test subsystem that comprises a target object <NUM> placed in the tunnel middle section, a test vehicle <NUM>, a brightness measuring device, a color temperature measuring device, a color rendering index measuring device, a speed measuring device, and a distance measuring device, for dynamic testing and static testing with test data collection; and a data computing subsystem that comprises a computer system for fitting and processing the test data.

In the traditional tunnel illumination, the illumination device <NUM> often adopts highpressure sodium lamps with a low color temperature. In the current tunnel design, LED and other new lighting sources are used, and these new lighting sources have selectable color temperatures and color rendering indexes. According to statistics, the light source color temperatures of tunnel lighting fixtures are mostly in the range of <NUM>-<NUM>. When there is a transition of light from warm white to cold white, there will also be a transition from yellow light sensation to white light sensation in visual perception, and thus the driver's visual recognition ability will also be affected. The fidelity degree of color is different under different color rendering conditions, wherein, a light source with higher color rendering performance has better reproducing effect of color, and thus the color seen by the human eye is closer to the natural original color, while a light source with low color rendering performance has poorer reproducing effect of color, and thus the color seen by the human eye is deviated to a greater extent. In the current tunnel design, the light source color rendering index of the lighting fixture is required to be not less than <NUM>.

In the system for implementing the illumination standard calculation method for a tunnel middle section based on safe visual recognition of the invention, the lighting fixture <NUM> adopts an LED lamp with adjustable color temperature, and in order to make the measurement convenient, the color temperature measuring device and the color rendering index measuring device are the same, being a luminance spectrophotometer.

In the system for implementing the illumination standard calculation method for a tunnel middle section based on safe visual recognition of the invention, the brightness measuring device is a luminance meter, and can also be an illuminometer, wherein the brightness value is obtained by using the relationship between illumination and brightness. For example, the average brightness value and average illumination value of the road surface is measured first, and then the road surface average illumination conversion coefficient is calculated and thus can be used in the conversion relationship between illumination and brightness, so as to obtain the brightness by measuring the illumination. In order to increase the efficiency and precision of the measurement, the speed measuring device and the distance measuring device are the same, being a non-contact speed meter.

Compared with a large bus, a small passenger car has relatively narrower field of vision. Under the same environment, it is even more difficult for drivers in a small passenger car to visually recognize the target object. According to the most unfavorable principle, the system for implementing the illumination standard calculation method for a tunnel middle section based on safe visual recognition of the invention selects a small passenger car as the motor vehicle <NUM>.

The drawings are only schematic and not to scale. Although the present invention has been described in combination with preferred embodiments, it should be understood that the protection scope of the present invention is not limited to the embodiments described herein.

Claim 1:
An illumination standard calculation method for a tunnel middle section based on safe visual recognition, comprising the following steps:
(f) substituting a value of safe stopping sight distance D<NUM> measured in meter corresponding to the maximum speed limit of the tunnel into the model formula <MAT> to obtain a value of dynamic minimum brightness value L<NUM> measured in cd/m<NUM> required for the tunnel middle section under this tunnel light environment.
(g) the tunnel being a simulation tunnel, placing a static test target object B in the tunnel middle section, parking a motor vehicle at a position that is spaced apart from the target object B by a distance Ds, and setting the color temperature of the light environment in the tunnel middle section to be T<NUM> and the color rendering index of the light environment in the tunnel middle section to be Ra<NUM> for the tunnel middle section;
(h) letting a driver enter the cab of the motor vehicle, adjusting the average brightness L of the light environment in the tunnel middle section from small to large, and recording the static minimum brightness value Lf required by the driver to visually discover the static test target object B;
(i) resetting at least one of the color temperature and the color rendering index of the tunnel middle section, repeating the step (h) to obtain static minimum brightness values Lf associated with a plurality of different sets of color temperatures and color rendering indexes, setting the static minimum brightness value Lf0 associated with a color temperature T<NUM> and a color rendering index Ra<NUM> as benchmark J, and comparing the benchmark J with static minimum brightness values Lf associated with different color temperatures and color rendering indexes to obtain the visual calibration coefficients a associated with different color temperatures and color rendering indexes;
(j) calculating the minimum brightness value L0d of the tunnel middle section under different light environments to be an arithmetic product of a and L<NUM>, which is the safe visual recognition threshold of the tunnel middle section.