# Reliability Enhancement Driven by ANN for Lighting Control System in Highway Tunnels
## 2 Research Status of Tunnel Lighting System
### Key Requirements of Tunnel Lighting System  
In tunnel environments, since access to maintenance of lighting components is limited and highly inconvenient, the reliable operation of lighting systems is of great importance. In general, an excellent lighting system should meet but not be limited to the following requirements:  
(1). It should be suitable for the geographical and climatic conditions of specific areas of the tunnel, and meet the relevant national tunnel lighting specifications, such as the \"Guide for the Lighting of Road Tunnels and Underpasses\" [11] and the JTG/T D70/2-01-2014 \"Guidelines for Design of Lighting of Highway Tunnels\" [12].  
(2). It should be equipped with the tunnel lighting lamps with high-quality design and production technology, excellent lighting output parameters and ease of maintenance.  
A circumstance that complicates the process of tunnel lighting is the presence of high humidity and waste gases in the air, the combination of which can lead to the formation of sulfuric or nitric acid. In environments such as this, luminaires are at high risk of damage. Regular maintenance can alleviate the problems, but closing the tunnel due to such works is impractical for logistical reasons and high costs. In such demanding environments, the design and quality of luminaires are vital, helping to protect them from penetration of fine particles and acids, resistance to vibration, and reduced likelihood of physical damage or overheating. Therefore, tunnel lighting demands are harsh on lamps, including design level, production process, and maintainability, etc., all of which must be outstanding to succeed within the parameters.  
(3). It should provide reasonable light environment indexes that help to improve the driving safety and comfort requirements in the tunnel area [13], which are also covered in the specifications in (1), for instance:  
* Color temperature and color rendering index.
* Luminance reduction factor.
* Uniformity of road surface luminance.
* Visual cognition distance.  
(4). It should possess some robustness and reliability features. Although there is no unified definition of standard of lighting system reliability, it can be evaluated according to the following aspects:  
* Greatly enhanced cyber security to ensure reliable operation and data transfer.
* Meet the highest tunnel safety standards to improve driver safety.
* Helpful to reduce traffic accidents and tunnel closures.
* Dynamic and real-time response to light conditions to help drivers' eyes acclimatize as they enter and exit the tunnel.
* Correct lighting levels at every stage.
* Manage lighting easily with intelligent control and online diagnostics.
* Less downtime and minimized disruption of traffic flow.
* Nearly always ready for unexpected events.
* Simple process to refurbish tunnel lights and upgrade components of the lighting system.
* Easy to manage and operate components of the lighting system remotely.
* Lower MTBF with both tunnel lights and control system.
* (5). It should align with the sustainability required by worldwide societal progress:
* Reduced carbon footprint.
* Decrease in maintenance costs.
* Enhanced driving experience and safety guarantee without significant cost increase.
* Balance of the main requirements of tunnel lighting, ensuring visual comfort and uniformity of light distribution, energy efficiency and ease of maintenance.