Master thesis : Biomimetic approach in the design of transport networks at city level. Case study: Brussels-Capital Region. (Eskander A. et al., 2021)

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Biomimetic approach in the design of transport networks at city
level. Case study: Brussels-Capital Region.
Alexandre Eskander (Université Libre de Bruxelles) – 19 août 2021 – eskanderalexandre@gmail.com
Directeur : Prof. Marie-Françoise Godart (Université Libre de Bruxelles)
Co-promoteur : Karim Lapp (Biomimicry Europa)
Keywords: Physarum polycephalum, biomimicry, transport network, spatial planning, urban mobility, sustainable mobility.
1. Introduction
The rise of the car in the major metropolises of the 21st
century has given urbanites freedom of movement, which
has come at a social, environmental and economic cost
over the years. In order to reduce the weight of the car in
cities, a logical solution is to increase the use of public
transport. One of the actions to be taken to make public
transport more attractive is a polycentric conception of the
city by strengthening the connections between the
different city centres. For as much as we distinguish which
centres we want to connect and how to connect them.
In applied mathematics and computer science, the question
of how to connect several points is explored by Graph
theory. A graph is an abstract set of objects in which
certain pairs of objects are related. Among the different
types of graphs are neighbourhood graphs. These graphs
are planar graphs in which two vertices are connected by a
segment according to a certain proximity. They allow the
study of proximity relationships between several points
and are therefore a useful tool in spatial network analysis
problems in land use planning.
As cities become increasingly complex and transform
themselves, classical spatial planning approaches may no
longer be sufficient to solve such problems in the future.
This thesis aims to modestly explore an alternative
approach based on biomimicry. These approaches consist
in taking nature (its forms, processes and functions) as a
model in order to respond to the challenges of sustainable
development.
2. Materials and methods
The biological material studied here is the unicellular
Physarum polycephalum. This organism, in its plasmode
form, visible to the naked eye, develops a protoplasmic
network linking several food sources. Over the past twenty
years, numerous studies have revealed the organism's
ability to develop networks similar to and sometimes better
constructed than the transport networks developed by our
societies. The exercise has been carried out to date on a
national or regional scale, but not yet on an urban scale.
The aim of this thesis is to examine how the organism
connects the different poles of the Brussels region and to
compare the results with a cartographic model and with the
existing network. We selected the 25 stations and
interchanges of the Regional Strategic Mobility Plan 2020-
2030 (Plan Good Move). For the map model, the two
networks connecting these 25 points were created using
Geographic Information System software (Quantum GIS
3.4 and GRASS GIS). The networks were constructed by
identifying the minimum spanning tree (MST) and the
Steiner tree problem (STP). For the biological model,
Physarum polycephalum was grown in solid medium (1%
Agar) in Petri dishes (Ø 90 mm and Ø 150 mm). We placed
an oat flake (food source) on each pole and inoculated the
organism at the Central Station in Brussels (see
Appendix). The experiment was carried out six times.

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3. Results and discussion
From a mathematical point of view, we did not obtain any
spanning tree (network connecting all the vertices)
contrary to the results obtained in the scientific literature.
However, structures similar to cartographic models
(minimum spanning tree) were observed, confirming the
capacity of the organism to elaborate a network at a lower
cost.
Figure 1 : Similarity between the protoplasmic network and the network
created by GRASS.
The organism has also constructed new nodes that are
similar to Steiner points and allow it to build a better
solution to the problem. Figure 3 compares the route
proposed by the organism to get from Ceria to Albert with
the route proposed by the STIB transport network.
The comparative analysis with the existing network
confirmed some known characteristics of the Brussels
transport network, such as the difficulties in connecting
with the south of Uccle, the difficulties between the east
and the west of the canal and the potential role of the
Flemish Region.
Figure 2 : Situation of experiment 1b after 72 hours.
Figure 3 : Comparison of the path between Ceria and Albert with the
protoplasmic network and with the Brussels public transport network
(Illustration on the left from Google on 7 August 2021).
To monitor the development of the protoplasmic lattice,
one of the six experiments was photographed every 600
seconds (10 minutes) in order to perform a time-lapse. The
result is available at the following link:
https://www.youtube.com/watch?v=T868l0cwaKU&t=1s
4. Limitations, perspectives and conclusion
We note several limitations that make the interpretation of
these results fragile. Firstly, despite the accessibility and
simplicity of culturing the organism, the experimental
conditions (outside the laboratory) did not prevent the
appearance of moulds after more than 72 hours. Secondly,
the origin of the strain of biological material does have an
impact in terms of the behaviour of the network
construction. This suggests the interest and necessity of
involving different expertise when trying to solve such a
problem under a biomimetic approach. Thirdly, we
interpreted the results from a comparative perspective.
Results based on more objective criteria (cost of the
network, level of resilience, etc.) would be recommended
to confirm or not the interest of developing such an
approach in spatial planning. Nevertheless, the results
obtained reinforce the idea that the natural world is full of
sustainable inspiration in many areas, including urban
mobility.
Background
This summary follows the submission of the final thesis for
the academic degree of Master in Environmental Sciences
and Management at the Université libre de Bruxelles
(ULB). The date of the defence will be Tuesday 31 August
2021 at 3 pm.
Isolation of
the“Gare de
Moensberg”(Comm
une d’Uccle)
New nodes
(Steiner
point)
Connection from
Bordet to
Commuauité via
the Flemish
Region
Ceria
(nouveau
noeud)
Veeweyde
Veeweyde
Parc des étangs
(nouveau noeud)
Parc des étangs
Albert
Gare du Midi

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Appendix: The 25 stations and interchanges of the Regional Strategic Mobility Plan 2020-2030 (Good Move Plan)
Illustration : Inoculation du Physarum
polycephalum au point 1 (Gare
Centrale).

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The 25 stations and interchanges in the Brussels-Capital Region's Strategic Regional Mobility Plan (Plan Good Move) include
7 national stations, 12 poles to be strengthened and 6 transfer nodes to be created:
- The national stations :
(1) Gare Centrale
(2) Bruxelles-Nord
(3) Schuman
(4) Bruxelles-Luxembourg
(5) Gare de Schaerbeek
(6) Bruxelles-Midi
(7) Gare d’Etterbeek
- The poles to be strengthened:
(8) Erasme
(9) Albert
(10) Herrmann-Debroux
(11) Merode
(12) Montgomery
(13) Meiser
(14) Roodebeek
(15) Bordet
(16) Gare de l’Ouest
(17) Simonis
(18) Basilique
(19) Heysel
- And the transfer nodes to be created :
(20) Veeweyde
(21) Moensberg
(22) Communauté
(23) Verboekhoeven
(24) Heembeek
(25) Gare de Jette