The original visualisation is a simple bar chart comparing the Percentage Index Score for Sustainable Public Transport. The score is based upon 23 indicators to give a ranking of each city in terms of the mobility and sustainability of their public transport system. The nearer the score to a 100% the higher the quality of their public transport system and the nearer to 0%, the lower the quality.
What did I like?
- The main title and sub-title are nice and clear.
- The flags are instantly recognisable.
- Bar charts are easy to understand.
- The percentage values are labelled directly in the bars, removing the need for an x-axis.
- The index definition is included for clarity.
What did I dislike?
- Bars are shaped like trains, making it difficult to discern where the bar ends, at the top or bottom?
- The transport images, whilst engaging are distracting attention away from the data.
- The icons at the bottom clutter the visualisation.
- The percentage index scores are very similar. The data for all the other cities with lower scores is missing, which would allow for a more interesting comparison.
- I only had limited time this week, so wanted to keep it quick.
- To create a simple and clean design, improving upon the clutter of the original.
- To create an exploratory visualisation, which allows users to select two cities for comparison.
- A design led approach sprung to mind using dough/donut charts, which reminded me of the wheels of a bus!
- I used a technique from the useful #Tableau Tip Tuesday archive courtesy of Andy Kriebel.
- The interactive version is available on Tableau Public.
Analysis of Dough/Donut Charts:
There is a comprehensive section on dough/donut charts in The Big Book of Dashboards (BBOD), (Wiley 2017, p400 – 403). In summary:
- Dough/donut charts are often used as alternatives to pie charts to show part to whole relationships. One slice shows the percentage of progress towards a target in colour and the other slice shows the remaining percentage of target to be achieved.
Dough/Donut Chart Pros:
- Good for key performance indicators showing percentage of target achieved.
- Useful for percentage figures as in this case with an upper boundary of 100%.
- Easier to understand than pie charts with several categories, as only two categories are compared.
- Arguably more interesting than a conventional bar chart?
Dough/Donut Chart Cons:
- Difficult to compare several dough/donut charts. In this case there are only two charts to compare so I may have just avoided the BBOD ‘screechy cat’ of bad practice?!
- Less useful for displaying over performance against target, which exceeds 100% of target.
There is a section in the BBOD on alternative approaches, including for example combining bar charts with dough/donut charts for a compromise solution.
I think I have achieved my goals in terms of creating a simple, clean interactive visualisation. It allows any city to be compared with any other city.
However it does not compare several cities together simultaneously like the original infographic.
Dough/Donut charts are not necessarily best practice but I think they are engaging to the audience.