Tunnels reduce the pressure of congested road traffic and minimize the distance from one location to another, providing a faster and more convenient mode of transit. Reliable and high-performance lighting is critical for safe travel in tunnels, which are darker and tighter than open roads. The tunnel’s enclosed environment may produce discomfort, anxiety, and terror. Drivers are unlikely to slow down as they rush through the tunnel as quickly as possible. Furthermore, the driver’s eyesight is hampered by the light contrast between the outside and interior of the tunnel. The combination of eagerness to get out of the tunnel and poor vision raises the likelihood of an accident.This article will discuss the zoning and installation of safe tunnel lighting.
Tunnel lighting is separated into five zones with varying lighting intensities to ensure optical adaptation and safety. The zoned tunnel illumination lowers brightness contrast and improves driver sight. However, the structure and size of tunnels differ. Inadequate installation can cause excessive glare and poor light dispersion. Tunnel lighting installations should thus fit the tunnel.
Safe tunnel lighting objectives
Tunnel illumination serves two purposes. One goal is to keep traffic entering, transiting, and departing the tunnel safe. The other is to ensure that traffic flows smoothly in the tunnel’s enclosed segment. Tunnel lighting should be adequate, comfortable, and of excellent quality in order to meet the goals.
Adequate illumination improves driver sight and provides great visual assistance. It also allows drivers to swiftly recognize traffic signs and potential hazards, lowering the risk of an accident. Tunnel lighting is designed to be flicker-free and glare-free. This necessitates adequate lighting levels tailored to distinct tunnel zones, as well as proper installation.
The key to high-quality tunnel illumination is accurate color rendering. Higher CRI lighting improves the actual appearance and features of the inner tunnel environment. Tunnel lighting that is qualified keeps traffic safe and provides a comfortable visual experience similar to driving on the open road.
Why is the tunnel lighting zoned?
It goes without saying that tunnel lighting safety is vital, but obstacles remain for safe tunnel lighting. The black hole effect is the most serious danger to safe tunnel lighting. Let’s look at the environment changes along the tunnel to figure out what’s causing the black hole effect.
Assume you are a driver on the open road (during the day) and there is a tunnel ahead. Because of the reflection of sunlight, the surrounding environment is bright. This makes you feel comfortable since you can see what’s going on around you. However, the tunnel entrance looks to be a black hole because it is much darker than the open road. The high brightness contrast obstructs your vision and jeopardizes your sensations of anxiety and uncertainty. You can adapt to the gloomy tunnel thanks to visual adaptation. However, visual correction takes time. Driving is hazardous during this time. Visual adaptation must occur at least before entering the tunnel. Otherwise, your vision will be hazy. After a while, you become accustomed to the lower brightness within the tunnel.
When you are ready to exit the tunnel, the lighting levels outside the tunnel are higher than the illumination levels inside the tunnel. Again, the contrast in brightness may impair your vision. To achieve visual adaptation, tunnel illumination is split into five regions with varying lighting level requirements.Lighting should be brighter at the entrance and gradually diminished inside the tunnel. The lighting level is enhanced at the tunnel’s exit.
5 tunnel lighting zones
According to CIE, the lighting requirement at a tunnel should apply to the outside lighting level as well as the point in the tunnel where visual adaptation must occur. Tunnel illumination is divided into five zones. They are the foundations for a safe and successful tunnel lighting system when planning tunnel lighting.
- Zone of access. The stretch area leading up to the tunnel entrance is known as the access zone. Drivers must be able to recognize potential hazards in this zone. In addition, visual adaptation must occur in this zone. The L20 method, which measures the average luminance within a 20° viewing cone of the driver’s sight, commencing from the access zone and centered on the entrance, is often used to compute visual adaptation. The driver’s visual adaption influences the lighting level in the next zone of the tunnel.
- Threshold area. The threshold zone is the tunnel’s entrance. It is the most critical zone for safety since black holes frequently develop in this zone. As a result, brightness must be steady and uniform throughout the initial section of the threshold zone before gradually decreasing. The lighting level at the threshold zone’s end can be decreased to around 40% of its initial value.
- Zone of Transition. The transition zone is the second section of the tunnel. The lighting level is gradually reduced in this zone to allow for visual adaptation in the next zone. The lighting level drop must not exceed a 1:3 ratio, which implies that the lighting level at the beginning of the transition zone must not be more than three times that at the conclusion of this zone.
- Interior zone. The interior zone is frequently the longest section of the tunnel. The amount of lighting in the interior zone is determined by the pace and volume of vehicles. The following table shows the recommended lighting settings for tunnels with varying traffic and speed.
- Zone of exit. The exit zone is the tunnel’s final section. The lighting level outside the tunnel is higher than that of the exit zone. Although the human eye can quickly adjust from low to high lighting levels, the exit may be obscured by the brightness contrast. As a result, the illumination level at the exit zone must be increased to help drivers to adjust to the bright outside environment. The lighting brightness in the exit zone should be five times that of the inside zone.
Tunnels | Recommended Light Levels |
Suburbs, low traffic, low speed (<70 km/h) | 1.5 – 3 cd/m2 |
Suburbs, high traffic, high speed (>70 km/h) | 2 – 6 cd/m2 |
Highway | 4 – 10 cd/m2 |
Urban | 4 – 10 cd/m2 |
Tunnel lights installation
Tunnel lights are commonly installed using either ceiling or wall installation. Aside from mounting methods, layout and mounted height have an impact on illumination performance. Inadequate installation might lead to uneven lighting distribution and glare. We must remember that each tunnel is unique. As a result, the answer to how to install tunnel lights varies. Knowing the effects of installation on lighting performance allows us to more effectively select the proper installation.
In general, ceiling mounting is appropriate for tunnels that are higher than the legal and minimal protection height. The opposite is true for wall mounting. In a specific range of mounted heights, the lower the mounted height and smaller the installation angle, the higher the road illumination and uniformity of lighting. Here’s a list of tunnel light mounting choices and their associated effects.
Yibai LED Lighting is a reputable manufacturer of LED lighting products. Just feel free to contact us for more information if you have any questions about your tunnel lighting projects.
