INDICATORS OF THE COMPACT CITY CONCEPT – NECESSARY DATA AND THE POSSIBILITY OF APPLICATION

One of the best-known attempts to measure the compactness of cities is the study by E. Burton [16]. As E. Burton pointed out years ago that the research on the compact city concept is difficult due to, among other things, the lack of clearly formulated indicators enabling the measurement of cities in terms of the selected concept. The author proposed 41 indicators, which she then tested on 25 English cities. The indicators were divided into three basic groups: density indicators, mix-of-use indicators, and intensification indicators. The density indicators group included 14 indicators in total, which were divided into additional subgroups: density of population, the density of built form, the density of sub-centers and density of housing. In turn, in the mix-of-use indicators group, 11 indicators were proposed concerning the provision of facilities (balance of residential and nonresidential land uses), a horizontal mix of uses (geographical spread of key facilities) and vertical mix of uses. However, in the largest group of intensification indicators, a total of 16 indicators were taken into account. These indicators were additionally divided into 4 subgroups: increase in population (re-urbanization), increase in development, increase in density of new development and increase in density of subcenters. Additionally, composite compactness indicators were proposed, taking into account 6 dimensions: “compact” (average of all compactness indicators), “dens” (average of all density indicators), “mixuse” (all mix-of-uses indicators), “intens” (all intensification indicators), “intpop” (all population-intensification indicators) and “intblt” (all built-form-intensification indicators) [16]. Summing up the set of indicators developed by Burton, it can be concluded that they constitute a very large group (41 indicators have been proposed in total) and in most cases, they refer to the compactness of urban structures. The proposed set of indicators is a valuable contribution to the research on compact city indicators, however, their implementation requires the knowledge of many precise data, often going beyond the framework of generally available statistics.

A set of indicators to measure cities against the compact city concept was also developed in the report “Compact City Policies. A Comparative Assessment” by OECD [12]. Importantly, the report was the finalization of a three-year project entirely devoted to the concept of a compact city. The OECD proposed a total of 18 indicators for monitoring and evaluating compact city performance, while case studies were developed for 5 selected metropolitan areas (Melbourne, Vancouver, Paris, Toyama, and Portland). The indicators were divided into two main categories, i.e. indicators related to compactness and indicators reflecting the impact of policies promoting a compact city on the environmental, social and economic spheres. For the first category, indicators were proposed related to [12] :

In the second category, however, a total of five indicators illustrating the impact of compact city policy on selected issues have been proposed:

Importantly, as indicated in the report, the above list is preliminary it is the result of a literature review, and some indicators need additional research and improvements. Due to the availability of data, only selected indicators have been included in the case studies [12].

Kotharkar et al. [23] also measured the compact urban form, and the case study concerned the Indian city of Nagpur (the largest urban center in central India). At that time, the following six groups concerning the urban form were proposed, for which indicators were determined:

Summarizing the next set of indicators, it can be noted that despite the different classification of key urban form characteristics, the indicators refer to similar aspects, i.e. density, transportation network and mixed land use [23].

Liaqat et al. [29], on the other hand, conducted research on the measurement of sustainable urban development in the light of the compact city concept. For this purpose, they also proposed a set of measurable indicators and a case study was developed for the Pakistani city of Lahore. Based, among others, on the aforementioned studies by Kotharker et al. [23], as well as on the results of interviews with experts, Liaqat et al. [29] developed a comprehensive set of indicators to assess sustainable urban development in the light of the compact city concept. The paper distinguishes three characteristic features, to which the following indicators have been assigned:

To sum up, the above list proposes a total of 10 indicators, characterized by a relatively easy calculation algorithm and a reference to three key assumptions: density, transportation and accessibility, and mixed land use.

The following guidelines have been followed during the work on the compact city index set (compare: Coombes, Wong [30]):

Based on the existing definitions and assumptions of the compact city concept (Table 1), as well as the sets of indicators developed by other researchers, five pillars of the contemporary compact city concept were proposed as a synthesis: city compactness, accessibility, public transport system with cycle and pedestrian communication, urban regeneration with the development of brownfield land and public spaces [10].

In this subchapter, tables from 2 to 6 present proposals for compact city indicators, taking into account the availability of the necessary data and the division into 5 thematic groups: city compactness, accessibility, public transport system with cycle and pedestrian communication, urban regeneration with development brownfield land and public spaces.

In almost every definition of the compact city, there is a concept of density. In research, both population density and building density appear. In addition, it is not uncommon to distinguish between net and gross population density/buildings. It should be stressed, however, that in the light of sustainable development and the contemporary compact city concept, relative density, adapted to the character and function of a given center, plays a key role. Available statistical data (both at the international and national level) enables the measurement of both population density within the administrative boundaries of the city and within built-up areas (after their determination). Also important is the trend in the development of these indicators. Table 2 presents proposals of indicators from this group. Importantly, intermediate analysis (e.g. developed areas) can be describe with superficial measures, however, the final indicators are numerical, usually expressed as a percentage.

As it is pointed out by Gasidło [27] a compact city should be analyzed not only from the point of view of its geometric shape but also the efficiency of land use and the quality of life of its inhabitants. Therefore, the intensity of use is insufficient. What is important, apart from density (as a characteristic feature of a compact city), there is also a postulate of mix land use. Currently, there is a return to the traditional design of multifunctional spatial structures, which facilitates access to the necessary functions and facilities (retail and service, educational, green areas, etc.). Therefore, accessibility (which is often referred to in the context of the compact city) is resultant mixed land use. The buffer analysis can be used to determine these indicators. At the beginning, the selected functions and facilities with access buffers (zones) should be determined (e.g. access buffer with a radius of 500 m). Then, it is necessary to estimate the share of residential area (one-family houses and/or multi-family houses) within the access buffers. At the final stage, the share of residential area in all designated access buffers should be summed up. Importantly, the proposed approach enables the analysis of the availability of the selected objects in the spatial aspect.

Relatively compact and multifunctional urban structures should be linked by an efficient public transport system, which is a key aspect of the sustainable development of modern cities. According to the OECD report, “a compact city implies higher intra-urban mobility and less automobile dependency” [12]. It is worth noting that the topic of transport is increasingly included in public statistics (e.g. within the Urban Audit program) [31].

Another important postulate of the modern compact city model is to develop inwards within the existing borders. In this context, the key role is played by the successive development of brownfield sites and their comprehensive urban regeneration.

The last element of a compact city is public spaces, due to the availability of data, a percentage of public open spaces, as well as generally accessible recreation and sports areas, are taken into account in this paper. Summarizing the proposed set of compact city indicators, it should be stated that the main sources of information on Polish cities are generally available statistics: international, national and local, as well as information made available by geodetic and cartographic documentation centers. An important source of information is the Topographic Objects Database. Simple GIS analyses enable both delimitations of selected areas, e.g. built-up areas (Figure 1) or green spaces (Figure 2), as well as research on accessibility, e.g. of public transport systems (Figures 3 and 4).

Figure 1.

Figure 2.

Figure 3.

Figure 4.