# Reliability Enhancement Driven by ANN for Lighting Control System in Highway Tunnels
## 3 Reliability of Tunnel Lighting System
### Dilemma to Balance Reliability and Sustainability  
With the evolution of tunnel lighting sources and control systems, together with the increasing complexity of current traffic conditions, the dependence of tunnel drivers' visual efficiency on lighting quality is further increased. The reasons listed above cause a rough transition between inside and outside light environments; this cannot satisfy the demand for the safety and comfort of tunnel drivers in real time. Lighting safety has always been challenging in the improvement of tunnel lighting system.  
As [PERSON] [32] points out, tunnel lighting is considered a paradoxical matter for two main reasons: firstly, complexity of driving in tunnels makes it almost impossible to create an installation satisfying all the potential users, and secondly, tunnel lighting is extremely expensive in economic, energy, environmental and even social terms. Safety and sustainable consumption have been somewhat inverse concepts in tunnel lighting. However, it was until the last decade that groups around the world seriously started to create reliable models and proposals to decrease the negative impact of these lighting installations while maintaining road safety in tunnels.  
Building a tunnel lighting system with coordinated reliability and sustainability and ensuring tunnel driving safety is one of the core tasks of TLCS. The main measures include the improvement of tunnel lamps and the enhancement of reliability of TLCS. At present, in terms of tunnel lamps, good results have been achieved through the large-scale deployment  
\begin{table}
\begin{tabular}{p{142.3 pt} p{142.3 pt}} \hline \hline
**Lighting Mode** & **Technical Characteristics** \\ \hline Fixed & Fixed control policy, takes no care for energy consumption. \\ \hline Time-series-based & Partially flexible control policy with time-series based on natural light statistics rule. \\  & Stable lighting mode with slightly lower energy consumption. \\  & Hard to track real-time changes in weather or natural light. \\  & Poor adaptability to emergencies. \\ \hline Initially intelligent with adjustable luminance & Illumination perception is introduced to help adjust the inside luminance at constant intervals with fixed reduction coefficient. \\  & Initially intelligent mode with lowered energy consumption. \\  & Unable to meet drivers’ demand for photochromic properties due to lack of perception with outside color temperature and regulation with inside color temperature. \\ \hline Intelligent with variable color temperature and luminance & The three modes above are unable to effectively reflect real-time changes in natural light, and it is hard to satisfy the physiological and psychological demands of tunnel drivers. \\  & This mode dynamically adjusts inside color temperature and luminance to track real-time variation of outside color temperature and illuminance. \\  & This mode strives to achieve energy saving and effectively improve driving safety and comfort. \\ \hline \hline \end{tabular}
\end{table}
Table 11: Evolution and technical characteristics of tunnel lighting mode.  
of LED lights. Additionally, reliability improvement of TLCS is mainly brought about by the intelligentization and informatization of lighting control systems.