## 4 Discussion and Future Research
If the properties of the geometrical model will be examined, the length of the edges (the distance between the examined CSDLs on the central ring and on the rays), the covered central area, the number of CSDLs per rays, the number of rays, their length, and the number of CSDLs per rays should be highlighted. Here, it is also very important to consider the different characteristics of the different CSDLs of different cities, the different traffic demands, and their deviation as well. Later, if the  
Figure 15: Designation of the reference geometrical model. currently two-dimensional geometrical model will be developed into a three-dimensional model, the terrain conditions (slopes) of the examined urban area will be important, it will be necessary to examine it in the ranking, with considering the altitude difference between the CSDLs on the central ring and on the rays. The other group to examine is the group of technology-based indicators. In the ranking methodology, exact, modeled cargo bike types should be examined instead of real types. In general, the most important indicators are the capacity, interchangeability of the cargo boxes, and the range (with or without assistance). In the case of a cargo bike without electric power assistance, the human factor must be considered as well, and the examination of the meteorological conditions is important too, as in the case of worse weather conditions, the open structure of the vehicles can have several disadvantages. If the terrain conditions are going to be examined as well, the capability of these modeled cargo bike types to handle slopes must be examined. For this evaluation, the delivery technologies can have three main groups:  
* two- or three-wheeled cargo bikes without electric power assistance;
* two-, three-, or four-wheeled cargo bikes (with or without trailer) with electric power assistance;
* non-pedal small electric delivery vehicles (e.g., cargo mopeds; they must be considered as their capabilities and advantages are very similar to cargo bikes)  
In such a ranking methodology, several indicators must be examined, so complex multicriterial models are needed in the future. Primarily, the plan is to use the Analytic Hierarchy Process method, as it is appropriate to handle such complex problems. In the next steps of the research, the exact definition of the criteria and the formalization of the ranking model will be the primary tasks. Regarding our plans, this model will be able to show the suitability of given cities for a geometrical model-based city logistics approach with the use of cargo bikes by comparing them with their reference model. In the future, it will also be essential to examine how to integrate the railway and waterway transport modes next to the road transport into the concepts of geometrical model-based thinking. In Figure 16 below, the previously examined system in Budapest has good railway and waterway transport connections, and the urban railways are even not marked--they can give lots of extra possibilities. Figure 16: The geometrical model of Budapest, with railway and waterway connections. In this paper, the city logistics system of the concentrated sets of delivery locations were examined, and only the business-to-business deliveries were included, from the suppliers to the stores of the CSDLs, via the consolidation center, using electric trucks and cargo bikes. Additionally, it can be very important to examine the other delivery types, primarily the business-to-customer deliveries (home deliveries, deliveries to parcel stations, or to parcel pick up points), but the deliveries between the stores of the same company and the deliveries to services should be examined as well.