How do I unpack the complex urban heritage transformation dynamics? THE SYSTEM DYNAMICSMAPPING ‘CAUSE’ AND ‘EFFECT’ REINFORCING AND BALANCING RELATIONSHIPS ON VENSIM

MAPPING ‘CAUSE’ AND ‘EFFECT’ REINFORCING AND BALANCING RELATIONSHIPS ON VENSIM

 

STEP 1

Download the Vensim software which can be downloaded for educational purposes for free from the following link: Free Downloads | Vensim

 

STEP 2

Draw ‘cause’ and ‘effect’ relationships as below. A detailed tutorial on how to do this can be found at the following You Tube video:

 

If we go back to the previous example, we will draw the relationships as below.

1. Open a ‘New Model’ from ‘File

 

b. Draw the first variable ‘connection of the market with the High Street’ (cause) by clicking on the symbol ‘A’. If you right click on the variable you have the option to include in shapes, or use different colours.

 

c. Draw the second variable (effect) i.e. Market growth

 

d. Draw the relationship by clicking on the ‘arrow’ button

 

e. Right click on the arrow to select the symbol of (+) or (-) depending on the relationship. In this case the symbol is (+) as the relationship is reinforcing. The ‘more’ the market connects with the High Street, the ‘more’ the market grows.

 

f. Now consider if this relationship returns back to the cause. In other words, consider if the ‘effect’ (market growth) is also a ‘cause’ for reinforcing the ‘connection of the market with the High Street’. In this case it is a logical assumption to make. Hence, we can create a reinforcing loop by clicking on the arrow that connects the ‘market growth’ with the ‘connection of the market with the High Street’.

 

 

g. We can insert a little label within the loop which might be of help later for communication purposes since our system will be growing consisting of many non-linear loops. To do this, we click on the ‘comment tool’ which has the image of a ‘comment’. A dialog box will open where we can type the type of relationship. This can the letter R for reinforcing or B for balancing relationship. A short description can be added that qualifies the relationship.

 

h. Now let’s draw the Balancing relationship (the more the Beresford square is pedestrianized, the less the market grows). We will use the same process as above. However, now the symbols will be different (the more +, the less -) and the label of the relationship will be different (i.e. B).

 

As you can see from the diagram above, we created a new ‘balancing’ this time loop which illustrates how the pedestrianization of the Beresford square was the ‘cause’ of the market decline (hence the symbol next to market growth is -). Based on information we have from the Survey of London it was the market growth that led to the pedestrianization of the Beresford Square and the rerouting of the buses. Hence, the ‘market growth’ is not just an ‘effect’ variable  but also a ‘cause’ variable.

 

i. We will now draw the last relationship we identified in the example shown in the previous section. This is a reinforcing relationship between ‘market growth’ and ‘buses passing through the square’. When we insert the new variable ‘buses passing through the square’ we immediately see how this variable is directly connected with the ‘connectivity of the market with the High Street’ but also with the ‘pedestrianization of the Beresford square’. Hence, the linkage of this variable with the ‘Market growth’ is an indirect one, rather than a direct one since it is the result of the previous interconnections. A new balancing loop is now formulated between ‘buses passing through’, ‘pedestrianization of square’ and ‘market growth’.

 

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