As the different physical and social factors usually affected the pattern and orientation of housing at the different locations in
the informal settlement, no global order might be seen in the settlement. But, in the most cases a global order might be
observed in the scale of each fragment. In this sense, the first settlers in the fragment construct their houses based on one of
the several settlement
’s spatial patterns refer to Table 1, and the newcomers mostly adhere to the accepted pattern in the
fragment and build the new houses with the same plan adjacent to the first houses in the fragment. Over time, the new settlers
who determined to construct their houses in the backside of the first row of houses in the fragment usually try to align their
houses parallel to the houses in the first row and so on. This goal-oriented self-ordering behaviour is formed in a collective
approach by the dwellers to optimize the occupancy pattern of the fragment.
3. DEVELOPING A FRAMEWORK FOR MODELLING
OF INFORMAL TRANSPORT INFRASTRUCTURE GROWTH IN THE CONTEXT OF INFORMAL
SETTLEMENTS
In the previous section, the emerged spatial pattern and morphology of the informal settlements have been studied in
detail. This study showed if the exceptional low-density dispersed housing pattern is excluded, generally it could be
observed that usually some degrees of order might be seen in the settlement spatial pattern of informal settlement in the
fragment level. In this context, to develop a framework for modelling of the growth of informal transport infrastructure in
informal settlements, two different dynamics have been identified in this study. The basic concepts of this new
taxonomy will be proposed in this study to ensure that the different dynamics in the formation of informal transport
infrastructure precisely differentiated and considered. In this term, indirect growth dynamic and direct growth dynamic will
be proposed as two effective dynamics in the formation of informal transport infrastructure in informal settlements and
will be discussed in the following sections. 3.1
Direct Dynamic of Informal Transport Infrastructure Growth
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.
Figure 5. Common Destinations that Placed Outside of Current
Extent of the Informal Settlement
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. To develop an agent-based model for simulation of direct
growth dynamic of informal transport infrastructure, the concepts of the previous studies by Helbing, et al.1997 and
Goldstone and Roberts 2006 for modelling of informal trail formation in the natural landscape can be adopted to develop a
more realistic model in the case of informal settlements. 3.2
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
This contribution has been peer-reviewed. doi:10.5194isprsarchives-XL-2-W3-273-2014
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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 hisher house according to hisher adopted pattern of housing in the first row of fragment, usually heshe considers a
void space as a path parallel to hisher 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 distances.
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, we suggest 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 behavioural rules of dwellers in the indirect formation informal transport infrastructure.
4. A PROTOTYPE MODEL FOR INITIAL TESTING OF
