# Efficiency Analysis of Roadway Lighting Replacement in a Selected Polish Municipality
## 3 Results  
### Analysis of the Existing Lighting System in a Selected Municipality  
The analysis of lighting replacement should start with analyses of the technical condition and the number and types of lighting currently in use. The analysis of the number and types of lighting poles installed in the municipality is presented below. One can obtain the number of street lighting poles from an inventory compiled in the municipality or conduct a site visit. In general, it is also possible to automatically verify and identify poles. The paper [18] presents an approach to the automatic recognition of street lighting poles based on mobile LiDAR data. In the method, point clouds were initially divided into above-ground and non-above-ground structures, and then by using the Euclidean distance clustering method, the non-above-ground point clouds were grouped into a series of clusters. The information on shape and intensity was also taken into account. In the end, a method based on GMM (Gaussian mixture model) was used for cluster modelling, where street lighting poles were recognised as compared to the street lighting pole models from the database created. The proposed method was tested, and experimental results show that the approach achieved a fairly high recognition rate of 90%.  
There are 487 lighting poles in the municipality in question. These are mostly pre-fabricated reinforced concrete poles (367 units) installed back in 1978 when they replaced wooden poles. The remainder are spun poles (120) installed in later years (2009-2010).  
There are 655 light points with a total capacity of 57.85 kW in the municipality. PHILIPS luminaires from the SGS-102 product family were used in the street lighting system in the municipality. The light source dedicated to this type of luminaire is MASTER SON-T high-intensity discharge (HID) sodium lamps. Both 100 W and 70 W lamps were used for lighting in the municipality. Most of the luminaires (511 units) were installed in 2009  
Figure 1: A simplified procedure in the method for analysing the effectiveness of road lighting system replacement and user comfort (source: original work).  
(Table 1). The remaining luminaires were successively replaced between 2010 and 2013 (an average of 64 luminaires per year).  
The wear rate of the poles was assessed according to Formula (1).  
\[S_{max}=\frac{W_{max}}{T}=\frac{44}{50}\times 100\%=88\% \tag{1}\]  
where:  
\(S_{max}\)--wear rate of the oldest poles;  
\(W_{max}\)--age of the oldest poles \(W_{max}=R_{o}-R_{m}=2022-1978=44\);  
\(R_{o}\)--current year;  
\(R_{m}\)--year of installation;  
\(T\)--useful life of the poles.  
The wear rate of the poles is quite high. As the oldest poles reach the end of their useful life, the older ones should also be replaced during the possible replacement of luminaires.  
It is generally assumed that the depreciation time for high-pressure sodium discharge lamps is approximately 20 years. The average wear rate of luminaires was calculated using Formula (2).  
\[S_{zo}=\frac{\sum_{i=0}^{n}\frac{W_{i}}{T_{o}}\times N_{i}}{\sum_{i=0}^{n}N_{ i}}\times 100\% \tag{2}\]  
where:  
\(S_{zo}\)--average wear rate of the system;  
\(n\)--number of replacement periods;  
\(W_{i}\)--age of luminaires replaced in year I;  
\(T_{o}\)--lifetime of the luminaries, it is assumed that T = 20 years;  
\(N_{i}\)--number of luminaires replaced in year i.  
By using the data collected in Table 1 and Formula (2), the average wear rate of the luminaires was calculated to be 62%. The calculated average luminaire wear rate indicates that the technical condition of the system is far from ideal.