# Efficiency Analysis of Roadway Lighting Replacement in a Selected Polish Municipality
## 3 Results
### Analysis of the Luminaires in Terms of Illuminance  
In addition to installation cost and time, user comfort is also a significant consideration. By using the possibilities offered by Building Information Modelling (BIM) and DIALux lighting design software, an analysis of the road lighting was conducted for the variants under consideration. According to [19], BIM is a working methodology for the management of building or civil works projects in which all the agents involved in the process work collaboratively and throughout the life cycle of the building. The authors of the model can use it at various stages of design and construction. Digital modelling tools in BIM enable one to create design variants. The data are represented geometrically and, using the right parameters, can be collated, sorted and displayed in a specific way while construction work can be planned. In addition to the properties of height, width and type of material used, geometry also has properties related to the manufacturer, the type of a given element, light intensity and the cost of a given element. The BIM model is built from commercially available elements in BIM libraries. Such elements can be arranged in different variants, and it is possible to obtain information on the number of elements of a given type to be included in a road lighting project. The model will make it possible to approximate investment costs for given poles and luminaires. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Variant** & **A1** & **A2** & **B1** & **B2** \\ \hline V1 & EUR 1,190,909,648 & EUR 1,956,827,819 & EUR 596,215,973 & EUR 979,187,454 \\ V2 & EUR 1,190,913,743 & EUR 1,956,831,914 & EUR 596,220,068 & EUR 979,191,550 \\ V3 & EUR 1,190,923,607 & EUR 1,956,841,778 & EUR 596,229,932 & EUR 979,201,413 \\ V4 & EUR 1,190,831,023 & EUR 1,956,749,194 & EUR 596,137,348 & EUR 979,108,829 \\ V5 & EUR 1,190,832,865 & EUR 1,956,751,036 & EUR 596,139,190 & EUR 979,110,672 \\ V6 & EUR 1,190,818,638 & EUR 1,956,736,808 & EUR 596,124,962 & EUR 979,096,444 \\ V7 & EUR 1,190,821,627 & EUR 1,956,739,798 & EUR 596,127,952 & EUR 979,099,434 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: NPVs for the various street lighting replacement options. Figure 2: Investment and operating costs for street lighting installations (source: original work). The creation of variants in the model enables smooth fine-tuning of the design concept. The designer will be able to efficiently change the type of luminaires and supports. This application of the BIM model enables one to effectively perform a cost analysis of a given design solution. The tabular data are regularly updated due to the parameters used in the model geometry, such as the following:  
* By changing a given luminaire for one-sided lighting, the costs of luminaires in the project will be updated for all lighting elements for the same number of luminaires, where a given luminaire also has a cost as a parameter;
* When replacing single-sided poles with double-sided poles, the cost of the option will change due to the use of a different way of road lighting; the number of supports will decrease, but the number of luminaires will also change. Figure 3 shows design variants for spun and reinforced concrete poles using single-sided and double-sided luminaires. An analysis of the road lighting will determine the number of lamps with given luminaires. Such an analysis can be performed in the DIALux application. However, one should always use applications that are compatible with each other. The paper [20] points out that not all applications are designed to cooperate due to different programming issues and data transfer methods. After importing data from the BIM libraries, it is necessary to check whether the virtual parameters are identical to the real ones. In this case, the individual lighting elements are imported into the application from the manufacturers' database.