Parking Lot Diagrams Revisited – Using Area to Show Effort
Six Project Trends Every PM Should be Aware Of

Project Progress, Optical Illusions, and the Simpsons

My last post was on modifying Parking Lot Diagrams to use the area of boxes to show the relative effort of differing parts of the system. The idea was that while traditional Parking Lot diagrams are a great way of summarizing progress at a project level, the customary approach of giving all the feature groups the same size box may lead people to believe these chunks of functionality are of equivalent size or complexity.

In the boxes below, the number in brackets describes the feature count, but this requires people to read the numbers and then consider the relative sizes. My goal was to create a new graphical summary that depicts the relative sizes via box area to make the summaries easier to understand.

So a standard Parking Lot diagram like this...
Parking Lot Diagram

becomes a scaled Parking Lot diagram like this...

Parking Lot Diagram Scaled

In the second example we can quickly see the relative estimated sizes of the areas of work, with for example, “Enter Order Details” being three times the size (in area) of “Create New Order”. In this example to keep things simple, I am using feature count (15 vs 5) to depict effort and area. Most projects will use development effort in points or person days as the scaling factor.

Anyway, I have been using these scaled Parking Lot diagrams on my projects for a while, created quite laboriously in Excel and PowerPoint, and I was hoping that someone with better skills than I have could help me streamline the process. Well, in typical fashion, soon after posting I learned that:

A)    I may be asking the wrong question
B)    My invented solution has already been done before and far more elegantly
C)    It has been done on the Simpsons

Oh, the joy of the internet! Actually this is of course a great thing and now I can progress from a much firmer foundation, and far quicker than my slow evolution was taking me...

When it comes to Excel acrobatics, Chandoo from the “Pointy Haired Dilbert” Excel and Charting web site is a great source of information, so I put the question to him. “How can I easily create the scaled Parking Lot diagrams in Excel alone?”  Chandoo was very helpful and gentle with his response and explained that people are not very good at discerning data displayed as area, and we can often build unintentional optical illusions.

In this example from Chandoo’s site, the orange circles are the same size, but because of the surrounding images they look dissimilar. For further optical illusions with data see his post here.
However, if we want to create scaled area graphs in Excel, here is Chandoo’s recommendation for doing so:
1)    First make parking lots for each of the activities in regular sizes.
2)    Also, in a table, list all the activities and their efforts (or costs / budgets)
3)    Now, create a live-preview of the parking lots using the camera tool. One image per parking lot. (more here )
4)    Name the images in some logical order (like imgTask1, imgTask2...)
5)    Now write a small macro that would scale the imgTaskn based on the effort required for it.
6)    That is all. You can use these sized images in your scope diagram or something else very easily.

Next in my search for showing how work components contribute to the whole project, and our relative progress against each category, I created a graduated pie chart diagram.

Progress Pie
Here the work areas are shown as pie segments, their pie size corresponding to their proportion of the whole project. Then progress in each area is superimposed as heavier colouring with a percent complete figure added.

It turns out this type of graph is a variant of a polar area diagram. Polar area diagrams are still sometimes called Nightingale Rose Graphs, after Florence Nightingale who is credited with creating them in 1858 to illustrate mortality rates in the Army.

Source: CoolInfoGraphics

A more recent use of a similar diagram has been created for the Simpsons 20th anniversary.   A combination Nightingale Rose Graph (polar area diagram), family tree and timeline, this chart connects the influences that impacted Matt Groening and the creators of the Simpsons as well as the shows that came after.

Source: CoolInfoGraphics

While these last two examples show factors other than percent complete against each segment it demonstrates how they can be used to create visually appealing charts that measure contribution to the whole and other characteristics.

However, the more I research, the more warnings I find like Chandoo’s. While visually seductive to people like me, folk are just not that good at understanding data represented as spatial areas.

Edward Tufte is a master of depicting data visually and an unabashed critic of many things visual. He is best known for his criticisms of PowerPoint presentations in his essay “The Cognitive Style of PowerPoint”.
PowerPoint Problems
Edward Tufte has this to say about Nightingale Rose Graphs:

“A Nightingale Rose by any other name would smell as foul?? These Nightingale Roses are also called "sector graphs", but to me they are just a type of pie chart and contain all the disadvantages of pie charts. What's wrong with pie charts? The only worst design than a pie chart is several of them, for then the viewer is asked to compare quantities in spatial disarray both within and between pieces." (Page 178, The Visual Display of Quantitative Information)

So what’s next for me? Well, being a visual, right-brain biased kind of person, I will keep looking (ha) for new ways to depict work aggregation and project progress. As I mentioned in my previous post, while Gantt charts can provide this information, there is in my experience, such a bad perception of them (perhaps because they are largely used incorrectly like PowerPoint) that they switch people off rather than inform and engage people about progress and issues.

I am still a fan of burn-down and burn-up graphs, in particular Cumulative Flow Diagrams, but they focus on the numbers (days, points, stories) rather than functional areas the business often relate better to. Like the dials and the windscreen in a car, we need both quantitative (data) and Qualitative (observed) metrics to get a balanced picture of data and progress towards a goal we understand and recognize.



In one of the volumes of "Quality Software Management", Gerald Weinberg suggests using a "task tracking diagram" (not the exact name). Draw an empty rectangle for each story/task with its left edge representing the day the task is supposed to start, and the right edge representing the day it is supposed to end. Fill it up with green on the days it is actually worked on, or leave blank to indicate its not being worked on. Extend the rectangle with red when the task is still being worked on after the day it was supposed to be finished.

Like many Agilists today, he suggests using low-tech tools like paper and markers and posting this on a wall.

I also think Weinberg's task tracking diagrams were meant for iterations or short projects, not for the whole project.

Bill Wake

Have you tried keeping the box width constant, so the eye compares the height of the box rather than trying to compare areas?

Mike Griffiths

Hi Ckeithray,

Thanks for the suggestion. from a quick Google it looks like volume three, I will pick up a copy and take a closer look. Many thanks for the suggestion.


Mike Griffiths

Hi Bill,

Thanks for the suggestion, I tried the opposite, keeping the box height constant, so the eye compares the box length, it worked OK, but looked a lot like a Gantt chart again, - these were the examples at the end of my original post. While bar graphs horizontally or vertically should not really make a difference, perhaps the vertical orientation is enough to fool us into thinking we are not viewing Gantt charts so therefore keep engaged. I will have a play and see how they look.


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