A) The role of road lighting
The purpose of setting lighting on the motor vehicle traffic roads in the city is to create a good visual environment for motor vehicle drivers, in order to achieve the goals of ensuring traffic safety, improving transportation efficiency, reducing criminal activities, and beautifying the night environment of the city. The purpose of providing lighting on pedestrian roads and residential roads mainly used by pedestrians and non-motorized vehicles is to provide pedestrians with a comfortable and safe visual environment to ensure that pedestrians can clearly see the type of road, the condition of the road surface, and whether there are obstacles; See clearly the vehicles that use the road at the same time, as well as their driving conditions and intentions, in order to understand the driving speed and direction of the vehicle, and determine the distance from the vehicle; when pedestrians meet, they can identify the facial features of the person on the opposite side and judge in time Its action intentions facilitate people’s communication and can effectively prevent criminal activities; the road lighting in this area can also provide appropriate auxiliary lighting for the characteristics and iconic landscapes of residential areas and the building number of residential buildings, which helps pedestrians The directions needed to locate and find the target. In addition, the road lighting in the residential area helps to create a comfortable and pleasant night atmosphere.
B) Visual characteristics of motor vehicle drivers and factors affecting road lighting
On a motor vehicle road, the driver’s field of view is composed of the carriageway, the surrounding environment on both sides of the road, the landscape in view, and the sky.
The visual information obtained by the driver is that any object on the road needs to be displayed against the portion of the field of view that constitutes the direct background. For example, obstacles on conventional road sections of a motor vehicle road appear in this way.
Pedestrians or other obstacles appearing on the road must be seen by the driver in time. Obstacles appear on the road and are seen in contrast to different backgrounds (such as roads with or without lighting, surrounding buildings, surrounding open areas, etc.). Although some surface features of obstacles may be obvious, under the bright background, these obstacles will still appear in the form of silhouettes. Information on the existence and location of road obstacles. Similarly, obstacles may be seen in the form of normal shadows on a dark background. In short, the driver captures information about the existence of these obstacles in a contrasting manner.
The visual conditions provided by road lighting are easily satisfied in dry road conditions. In the wet state, the uniformity of the brightness of the road surface decreases. This situation leads to increased sensitivity to glare and reflection from the dazzling surface of the wet area, and also generates glare.
Fog obscuration is related to fog density to some extent. On high-speed roads, the speed is generally high, and in the case of irregular fog, it often leads to dangerous situations. Under misty conditions, good lighting can provide information about the immediate environment and provide guidance for the roads and roads of the road. very important.
The viewing ability decreases as the driver’s age increases, which is the result of three effects. First, the penetrating power of ocular media decreases with age, such as 28% of those who are only 25 years old at 70 years old. Secondly, the scattering of light in the eye medium increases with age.This scattering weakens the visual contrast of objects.For example, in a 70-year-old person, the scattered light represented by the equivalent light curtain brightness is 25 years young 2.5 times that of people. The result of these two effects is to identify targets, and older people need higher contrast thresholds. Therefore, a 70-year-old observer needs approximately three times more contrast at the threshold of visibility than a 25-year-old observer. Thirdly, the density of retinal photoreceptor cells (receivers) decreases with age, which reduces the eye’s ability to discern details, even if the eye is refractively corrected. Therefore, on average, a 70-year-old observer has only 66% of the visual acuity of a 25-year-old observer.
With the increase of age, the process of cognition of people’s psychophysics becomes slower, and older drivers need more time to make judgments. Therefore, it is necessary for vehicles to travel longer distances in order to respond to the traffic conditions ahead.
All these factors will lead to more night accidents for older drivers, even if the total number of older drivers is small.
When the driver is driving, there are many factors that will affect the timely capture and judgment of visual information, so it is necessary to adjust the lighting level accordingly according to the existence, type, size, etc. of these factors. These factors include the speed of the driver, the volume of traffic on the road, the composition of traffic on the road, the mix of different types of road users, the completeness of road facilities, the completeness of traffic security facilities, and the intersection on the road The distribution density of intersections such as crosswalks, whether there is a parking zone in the edge area of the road, the types and distribution of brightness sources and their sources, and the visual guidance on the road.
In summary, these factors should be considered when determining the level of lighting design standards.
C) Road Classification
In order to confirm how much lighting is needed on a sub-segment road, you need to know the type and grade of the road, and provide the corresponding lighting in our country.The classification of urban roads is based on the status of roads in the urban road network, traffic functions, and along the route. The requirements of buildings and service functions of urban residents divide urban roads into expressways, main roads, secondary roads, branch roads, and residential roads. These road divisions are defined as follows.
Expressways: Roads with long distances in the city, heavy traffic, and services for fast traffic. An intermediate lane is set between the opposite lanes of the expressway, and the central division is implemented, all access is controlled, and the distance and form of the entrance and exit are controlled. Continuous traffic should be achieved, with at least two lanes set up in one direction, and supporting traffic safety and management facilities. Entrances and exits to public buildings that attract a lot of traffic and people should not be set on both sides.
Main road: The main road connecting the main districts of the city with transportation functions as the main road. It adopts the form of separation between motor vehicles and non-motor vehicles, such as three-way roads or four-way roads. It is not appropriate to set up entrances to public buildings that attract a lot of traffic and people.
Sub-road: Combined with the main road to form a main road network, the road with the function of collecting and distributing traffic as the main and serving the function.
Branch road: The connecting road between the secondary road and the residential area road. It is connected to the secondary roads and roads in the area (industrial areas, residential areas, transportation facilities, etc.), and solves local area traffic, mainly serving functions.
Roads in residential areas: Roads in residential areas and streets mainly used by pedestrians and non-motorized vehicles.
Expressways, main roads, secondary roads, and branch roads.Although lanes for non-motorized vehicles and pedestrian paths for pedestrians are generally set on either side of them, according to their main functions and forms, these roads are still collectively referred to as machines Motor vehicle roads.
The suggestion of the relevant technical documents of the International Lighting Commission is to directly consider those factors that affect road lighting on the road, and determine the corresponding lighting level and the amount of lighting required according to the degree of influence of these factors.
The 8 factors that affect road lighting summarized by CIE are: driving speed, traffic flow, traffic composition, the isolation of different types of traffic lanes, the density of road intersection distribution, whether roadside parking is possible, environmental brightness, night Visual guidance on the road, etc.
The designer should go to the road site to inspect these factors, and quantify each factor (parameter), see Table 18-1.
By superposing the weight coefficients of each road influencing factor, the total influencing factor WF can be obtained.