Sometimes, how you present the information is more important than the information you present.
When I started doing large-scale parking demand analyses as the Great Recession lifted, the “industry standard” was to graph parking demand using bar charts. Each hour that demand is observed is plotted on the horizontal axis, and for each hour a bar is plotted; the height of that bar is proportional to the percentage of observed spaces that were occupied at that hour. It’s a bit of a mouthful to explain, and a bit of an eyeful to observe. Take this example, produced by “a rival firm” for a parking study in Central Portland:
Yuck! There are a number of elements about that presentation that feel awkward (aside from the artifacts of scanning, of course), the most obvious of which is that it uses a ton of “ink” to convey a relatively little amount of information in violation of one of infographic guru Edward Tufte’s cardinal rules. But even more than this, you can look at charts like this over and over again and never notice a pattern among the noise. The presentation as a bar chart doesn’t really allow for one of the human brain’s best assets—it’s pattern recognition superpower—to take over.
We can solve both of these inefficiencies simply by graphing the data with a humble little line instead:
Even though the pattern between the old bar chart and new line graph are relatively similar, notice that it’s a lot easier to spot the basic trends and understand what’s going on in the bottom one. In particular, you can see that there are two peaks, with one occurring in the early afternoon and a second one in the early evening. And in addition to being easier to recognize patterns with line graphs, by squishing all of the info previously shown in bars into a tight little line we can devote our remaining ink and space to conveying additional info, in this case the enforcement hours (in blue), the City’s target occupancy range (in green), and their maximum acceptable occupancy (the red line at 85%).
What’s interesting is that, no matter where we looked in Central Portland, we saw some manifestation of this pattern. For example, here’s one from the Pearl District:
Since the pattern popped up so often, it needed a name. Hence, Camel Curves:
While the “camel reveal” is always good for laughs when talking about an otherwise dry topic, I think it actually provides a useful framework. The number of humps—are we talking about a Bactrian or a Dromedary camel?—size of the humps, and depth of the valley between can be used to divine a lot of information about what’s driving parking demand. For instance, you can see that the Pearl District’s two-humped camel is largely similar to downtown Portland’s, except that rightmost hump on the Pearl District’s camel rises up a bit higher. This tells us that it’s a relatively similar mix of uses driving demand in both districts, but the Pearl’s demand is more driven by evening-heavy uses like dining and shopping than downtown.
Eventually, we came to realize that the two-humped pattern we saw throughout downtown Portland was virtually inevitable in dense, mixed use districts where multiple types of land uses drive parking demand. Indeed, all the way across the country in Uptown Charlotte, North Carolina, we spotted a strikingly similar one. It’s got a lot in common with the curves spotted in downtown Portland and the Pearl, which tells us that it’s a similar mix of land uses driving the demand. And likewise, the subtle differences spotted between camels reveal important differences: In Charlotte, the sharper peaks result from relatively more demand being driven by restaurant and retail uses than in Portland, as a larger stock of off-street parking in the Queen City absorbs a greater share of residential and commuter demand:
Of course, when we start to get away from mixed-use areas, we start to see single-humped camels. Take a look at Cannon Beach, Oregon, where the big, beautiful ocean is the biggest driver of demand. The single peak happens in mid-afternoon, when beach demand is the highest, although the restaurants and entertainment in the tourist town ensure that the midday peak is not terribly pronounced:
It’s perhaps a bit kitschy, but I have yet to see a parking demand curve that deviates too far from the shape of a camel’s back…and I look at a lot of parking demand curves. But I think the underlying point is quite important: By presenting our data in an articulate and appropriate format, we are able to recognize patterns and glean insights that do not reveal themselves through more clumsy presentations. That’s why we take tremendous pride in our graphic design and presentation of information at Studio Davis, and how we simply get better engagement and more buy-in during parking planning processes than other firms can even dream of.