Transport Data Dashboard: Methodology
What are the data sources?
The data underpinning the Transport Data Dashboard is collected from multiple public sources, including data supplied to the International Transport Forum by its member countries. The data series spans from 2000 until the most recent year with available data. The data is freely accessible and should be cited as ITF (2022), "Transport performance indicators (Edition 2021)", ITF Transport Performance Indicators, https://stats.oecd.org/Index.aspx?DataSetCode=ITF_INDICATORS.
Which countries are covered?
The Transport Data Dashboard covers countries with data available for the chosen categories. If no data is available for a selected dimension, that country's score will not be displayed. These can vary depending on the data available and the composition of the dimensions chosen by the user. For example, suppose a user has attributed a weight of more than zero to Road Safety but country X has no data for this dimension, then no compound score will be calculated for country X for comparison.
How are the weights assigned?
Users set the weights for each dimension of the Transport Data Dashboard by setting the value for each dimension between 0 ("not important") to 5 ("extremely important"). The assigned values are converted into weight coefficients on a scale of 0 to 1. The weight coefficients for dimensions are calculated by dividing the attributed score of the category by the sum of the values given to all categories. For example, suppose a user assigns a 5 to Road Safety and a 3 to all the other six categories: then, Road Safety will be weighed by a factor of 5/(5+3*6) (i.e. around 21.7%) and all the other dimensions by a factor of 3/(5+3*6) (i.e. around 13%). The sum of all weights is 100%.
How are the indicators normalised?
To compare and aggregate values expressed in different unities (e.g. US dollars or kilometres), the indicator values are normalised. The normalisation is done with a standard formula that converts the indicators' original values into numbers varying between 0 (worst performing) and 1 (best performing).
The formula is:
value to convert – minimum value
—————————————————
maximum value - minimum value
When an indicator measures a negative component (e.g. road fatalities), the formula used is:
value to convert – minimum value
1- ————————————————
maximum value – minimum value
From a sustainable development perspective, we classify indicators based on whether they measure a positive or negative component.
How are the indicators aggregated?
Each dimension is represented by several indicators. After normalisation, indicators are averaged with equal weights. For instance, category A is measured with indicators A1, A2 and A3. Category A's score will thus be given as follows:
A1+ A2+ A3
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3