# Implementation of the 3-30-300 Green City Concept: Warsaw Case Study
## 2 Materials and Methods  
### Methodological Foundations  
The proposed methodology was based on the 3-30-300 [22] concept, which thoroughly analyzes cities in terms of the accessibility of green areas. This idea assumes that from every window of a building, at least three trees should be visible. Additionally, each district should have at least 30% of its area covered by greenery, and every building should be within a maximum distance of 300 m from the nearest park or forest. This concept was developed by a professor from the University of British Columbia in Vancouver, and its practical application was demonstrated by a group of researchers [23]. The aim of their study was to assess the accessibility of green spaces for residents of Florida based on a survey conducted among 1716 residents. The research confirmed that green cities are crucial for the quality of life of their residents, but it did not specify how exactly one can determine whether a part of a city or a specific residential building actually meets its criteria. The results were based solely on residents' opinions, rather than on specific, measurable, and verifiable conditions. Against the background of the sometimes very detailed concepts of green city research cited in the introduction, the 3-30-300 concept seems quite simple and very clear. Its advantage is that it takes into account the basic aspects of access to green spaces that are common to all countries. Firstly, it includes the aspect of green space visible from each home, which gives a sense of proximity to the green environment. Secondly, it takes into account the aspect of close access to public green spaces, such as a park. These two aspects are the basis for thinking about a green city. Above all, they seem to be easier to implement than other concepts. However, this concept is not without its shortcomings. First, it defines three logical, very basic criteria: 3 trees, 30%, 300 m. But it defines them in very general terms, without providing the detailed parameters necessary for their implementation. The most important missing detail is the distance from which 3 trees should be visible. They could be visible from 10, 20, or 200 m. What distance is valuable? Furthermore, the concept does not specify what counts as \"green areas\". Can we consider as green areas only wooded areas, but also lawns, flower beds, etc.? These parameters are crucial for the implementation of the concept and, consequently, for the results that indicate whether the city under study can be considered green. Given these factors, this study proposed refining all the conditions of the 3-30-300 concept and utilizing spatial analysis methods to precisely, repeatably, and unambiguously determine which buildings meet the criteria of a green city. First, the condition of being able to see three trees from a window was clarified. This criterion should involve the distance between the window and the trees, ensuring that the trees are visible in the immediate vicinity of the home, rather than kilometers away. Therefore, it was assumed that \"three trees visible from the window\" should only include those within a distance of no more than 20 m from the building. This is a fairly large value, assuming that the trees do not have to be in the immediate vicinity of the building; they can be a bit distant. The second parameter that was refined was the definition of \"from every window\". This means that the study should not only consider the building as a whole but also its various sections, as apartments located on different sides of the building may have different degrees of access to greenery, particularly trees visible from windows. In order to put this parameter into practice, an original method was developed. Due to the lack of detailed data on the placement of windows in buildings, it was decided that the distribution of apartments should be simulated. This simulation was conducted by dividing each residential structure into squares with sides of 15 m, representing apartments in multi-family buildings.