Taikichiro Mori Memorial Research Grants

 Graduate Student Researcher Development Grant Report

February 2015


Research Project: Organic Infrastructures in Human Settlement Systems: Towards a Generic Spatially Explicit Model to Simulate Informal Path Formation Process in a Self-organized Landscape

Researcher: Hossein Vahidi

Affiliation: Graduate School of Media and Governance, Keio University, Japan

Email: vahidi@sfc.keio.ac.jp


Human settlements have been classified into those which have been grown in an unplanned and organical process and those which have been developed in a planned and artificial approach. In the organic method of human settlement expansion, the settlement has been grown mainly based on continues collaborative activities of the residents in evolutionary approach overtime without any top-down planned approach.

The organic structure can be observed in the human settlements in two forms: The historical organic textures in rural and urban planned settlements and the informal settlements.

Some of the historical districts in the planned rural and urban areas were expanded as the result of an unplanned process through the history. These types of residential areas have been expanded in an informal process until the recent centuries and decades when the role of the government and public sectors in the top down planning of the settlements has been increased. Therefore as the unplanned approach of urban growth has been transformed to the planned approach in these settlements in the recent era, the organic growth in these historical settlements has been mostly stopped at present. However, as this type of available organic structures have formed the backbones of the new planned settlements, the irregular patterns in the form and morphology of them still can be partially or totally observed in some of the recent settlements.

In contrast with the organic historical textures where the growth process of them usually has been stopped long time ago, the informal settlements are live examples of organic growth of the settlements in our era.

Lack of access to proper transportation infrastructure is one of the main characteristic of the settlements where expanded organically and in unplanned approach.

In the absence of developed formal infrastructure in the unplanned settlements, the informal network of infrastructure will be formed by settlers. This informal human trail network undertakes the role of connection between significant destinations and also provides the accessibility of zones and facilities for settlers in the settlement (Figure 1, Figure 2).

 Informal formation of human trail system between an origin and a destination has a bottom-up nature. Basically, the process starts when a track is created by a single settler in the form of physical signs like compacted ground or damaged and trampled vegetation.  This track will be developed into a footpath if it has been used frequently by many people.



Figure 1. Informal Infrastructure in Informal Settlement



Figure 2. Informal Infrastructure System, Dar es Salaam, Tanzania


Not only in the settlements with organic and informal nature of expansion, but also the informal trail formation process can be observed in formal and planned environments (Figure 3, 4 & 5).

A desire path also known as a desire line or social trail is a technical term which has been applied for a path that formed as a consequence of pedestrians walking in the formal urban environment by urban planners for almost a hundred year.


Figure 3. Informal Infrastructure Formation in a Planned Environment, Beijing, China



Figure 4. Informal Infrastructure Formation in a Planned Environment, SFC Campus, Keio University, Fujisawa-shi, Japan


Figure 5. Informal Infrastructure System in a Planned Environment, SFC Campus, Keio University, Fujisawa-shi, Japan


Previous agent-based models for simulation of infrastructure growth mostly concentrated on the modelling of planned and structured infrastructure growth that are emerged in a top-down approach. So, the existing agent-based models cannot fully handle the simulation of the informal growth and organic growth of infrastructure in the unplanned and planned settlement.

To address the above-mentioned research gap, this was studied the formation of informal infrastructure under two main categories.

In the first category, the Direct Dynamic of Informal infrastructure growth have been studied. Direct dynamic of informal transport infrastructure (trail system) formation from an origin to a destination has a bottom-up nature. Basically, this process starts when a track is created by a single settler in the form of physical signs such as the compacted ground or damaged and trampled vegetation. This track will be developed into a footpath if it has been used frequently by many people.

Bottom-up process of direct growth in infrastructure system is initiated from the different daily behaviours of settlers and is influenced by various social, economical and physical factors.

This dynamic of trail formation is basically the predominant dynamic of path formation between origins and destinations in the informal settlements, however during the middle stages of extension stage in informal settlement (construction of new houses in the open space of the settlement) and latter during densification (infilling) stage of formation and growth of the informal settlements, most of these trails will be disappeared.

In this context, the buildings would be built on the track of footpath if that footpath has used only by a few number of dwellers and not consolidated enough in the settlement. Therefore, at the middle stages of extension dynamic and at the beginning of informal settlement densification stage in the growth process of informal settlements, mostly the considered void spaces by the dwellers between the dwellings will take the burden of channelizing and addressing the daily trips in the settlement (for more details see section 3.2).

Consequently, in the informal settlements with dense and bounded configuration and rapid rate of growth, the direct dynamic of informal transport infrastructure formation might be neglected (if only we need to model and simulate the final pattern of infrastructure system and final spatial pattern of the settlement) in the most cases, as usually they do not have a considerable effect on the final emergent spatial pattern of informal infrastructure and the spatial pattern of informal settlement.

However, in some exceptional cases, the direct dynamic of informal transport infrastructure formation may considerably affect the final emergent spatial pattern of informal infrastructure and the spatial pattern of informal settlement.

In first type of these exceptional cases, the informal infrastructure is formed between the informal settlement to a common destination between the different dwellers (such as water well, formal road etc.) located outside of the current extent of the settlement. In this context, if the informal path has been used frequently by the different dwellers frequently, the formed trail has a chance to be consolidated over time. In this sense, a well consolidated trail has a high chance to be recognized by the newcomers as a major path that should be preserved in the horizontal growth stage of informal settlement (Figure 5). This type of informal transport infrastructure can have effective impact on the future direction of horizontal growth of informal settlement and as therefore the spatial pattern of informal settlement as the newcomers usually interested to construct their houses adjacent to the consolidated paths.

In addition to this, an informal infrastructure that is emerged based on the direct dynamic also might be preserved in the informal settlement with a dispersed pattern or in the settlement with an slow growth rate if the path is frequently used by several dwellers overtime and the trail would find the chance to be consolidated enough and to be recognized as a major path before the construction of new dwellings over the free space.

The formation of desire path and the infrastructure in the formal settlements also follows from Direct Dynamic of Informal infrastructure growth. The trail formation process triggered when a track is created by a single pedestrian in the form of physical signs in the background of environment and overtime, this single track will be developed into a footpath and a trail if it has been used frequently by many pedestrians.

So for simulation of the direct dynamic of infrastructure growth, a spatially explicit agent-based model has been developed to simulate the human logic and behaviors in the formation of informal trails under the different settings of environmental conditions in a Self-organized Landscape (Figure 6).

Figure 6. Informal Infrastructure Formation in a Planned Environment, Brasilia, Brazil (Left). Result of Agent-based Simulation of Informal Infrastructure Formation in Study Area (Right)


In the other level, this research studied the Indirect Dynamic of Informal Transport Infrastructure Growth. This dynamic mainly is observed in the settlements with almost ordered settlement’s spatial pattern (with non-dispersal spatial pattern) in the fragment level which have bounded extents with a fast extension and densification dynamic. For modelling of the final pattern of informal transport infrastructure in this type of settlements, the formation of informal transport infrastructure could be considered as the function of settlement construction (housing) dynamic. Based on this definition, when a settler constructs his/her house (according to his/her adopted pattern of housing) in the first row of fragment, usually he/she considers a void space (as a path) parallel to his/her house and this trend has been adapted by other new dwellers in the first row of houses construction in the fragment. This system also adopted by the next settlers at the next row of construction in the fragment and so on and in this sense the transport infrastructure is indirectly developed and penetrates between the houses in the term of void spaces to provide the accessibility of building blocks. For connection of two parallel contiguous building rows (or dwellings) and providing the basic or secondary accessibility of them, usually, the void space (s) has (have) been considered between two rows by the dwellers in the appropriate distance(s).

To our knowledge, in the context of fine-scale modelling of the informal settlement growth, up to now, only two research have been conducted by Iqbal (2009) and Augustijn-Beckers, et al. (2011). In both of these proposed models, the spatial pattern of informal infrastructure was fully adopted from the final state of transport informal infrastructure in the reality. Therefore, for the means of simplification, they assumed that the informal infrastructure has a static nature and fully existed in the area at the beginning of simulation, therefore they only concentrated on developing a model for fine-scale simulation housing (extension and infilling dynamics).

In this context, it was suggested that the current existing fine-scale housing models can be developed by a sub-model for modelling of the indirect informal infrastructure growth pattern (in the context of creating the void spaces in the settlement) to improve the current settlement growth models by considering the realistic behavioral rules of dwellers in the indirect formation informal transport infrastructure.

It was mentioned that the indirect growth dynamic of informal transport infrastructure could be considered as a sub-dynamic of informal housing dynamic. As the existing developed models for simulation of the informal settlement growth are not available for us, so in the absence of these implemented models, a simple and limited agent-based model has been developed and implemented as a prototype to model the housing mechanism in the context of informal settlement in order to test the validity of the proposed dynamic for the indirect growth of informal transport infrastructure (Figure 7, Figure 8).

Figure 7. Satellite Image (Left), Transport Infrastructure Map (Right); Manzese, Dar es Salaam, Tanzania


Figure 8. Result of Simulation for Different Runs of Prototype Model


The output of this study has been published partly in the International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XL-2/W3, 2014, another comprehensive paper has been prepared to submit for a scientific journal. 
Finally, I would like to take this opportunity to express my sincere gratitude to Mori Fund Steering Committee for selecting me as one of Mori Grant recipients and provide this unique opportunity for me to conduct this research.