Human Irrationality 3 – Parking

                One day this past week was the first time this season that I had to scrape frost off my windshield. Anyone who’s seen how my hands react to cold air would know that I naturally wanted to spend as little time out in the brisk morning air as possible. When I pulled into the parking lot at my office, I, for the first time ever, really thought about what spot would afford me the shortest walk into the office. Like many, I had always naturally gravitated to what I thought was the closest spot, but until this past week I did not realize that I had been doing a pretty poor job of minimizing my walk from the car to the destination. Upon this realization, I started looking at the parking patterns of others and realized they make the same mistake I always did.

                To find the best available parking spot, you must first start by establishing the destination – typically the entrance to the building, or a single crosswalk that feeds the entrance. This is the convergence point – the one point that everyone in the lot must walk to before their paths diverge inside the building. The shortest path to this destination will give you the shortest path to wherever you’re going within the building. Parking lots that access multiple entrances make things a bit more complicated, so we’ll focus on single entrance lots (though the method I will explain can be extrapolated pretty easily).

                Now that we have the destination established, we can create fronts where all spots that fall on those fronts require the same walking distance to the entrance. The natural first pass at this will be to draw a circle that’s centered at the convergence point, as shown below. If any spots are available within the front, they should be taken before a spot outside the front.

This circular arc works well if the parking lot is empty and you can walk in a straight line from your car to the destination, but often this is not the case. To look at the other extreme, let’s assume you either walk parallel to the rows of cars, or perpendicular to them while walking through the lot. If this is the case, a line that’s 45 degrees from either of the walking distances will give the front of equidistant parking spots.

                In reality, you will probably walk mostly parallel or perpendicular to the car rows, but with a spot or two where you walk diagonally. In this case, the front will bow out and be somewhere in between the two pictured above. This is a bit less concrete, but, as I will now explain, neither are followed, so our parking patterns are imperfect either way.

                Since I made this realization, I have looked at parking lots I entered to figure out the general pattern they tend to fill up. I’ve found that the typical semi-full parking lot looks something like this:

The cars certainly do gravitate to the row closest to the entrance, but not as much as they should. The rows that are a few over start filling up before it makes sense for them to. Note: there are always some cars that will park farther away, but we can ignore those since they clearly aren’t trying to find the closest spot.

                My best explanation of why people tend to park in this way is that they value being close to the building more than they do being close to the entrance itself. A driver who isn’t specifically thinking about the closest parking spot to the entrance will see a spot close to the building but a few rows from the entrance and conclude that it is closer to the entrance than it really is. People typically value a short walking distance towards the building than they do a shorter walking distance parallel to the building. This is hardly surprising, because the building is where they are going; they just fail to understand that the entrance is the real key to minimizing the walk, since it's the only way into the building (unless you're a ghost, of course).

                Finally, instead of taking my word for it, let’s look at a real life example, courtesy of our friends over at Google (bonus points for anyone who can guess where this parking lot is):

You can see that no matter which front we look at, there are cars starting to populate the area beyond or just barely within the front when there are still spots well inside the front. And before anyone uses the excuse that people are looking for spots that you can pull through and not have to back out of – there are several of those available in the inner rows.

Bonus thought of the day: Stout & Porter are very similar beers; Stout & Portly are very similar adjectives.