Unlearning the things you thought you knew

Why our solutions to planning problems are often worse than the bread crust your mother used to make you eat

Stephen Corwin
Dec 1, 2014 · 7 min read

I think I finally grew up the moment I realized that even the right answers could be wrong. As a child, it seems as though all decisions are made by some power so unfathomably superior to you that they are more or less the word of god. Those are the years where you pick up the do’s and don’ts in life, little tidbits of conventional wisdom that teach you how to function in this world like “don’t touch the stove, it could be hot,” “say thank you to that person who just helped you,” or “don’t forget to eat the crust, since it’s the healthiest part.”

Wait what?

It wasn’t until years into my adulthood that I actually considered that last one. The crust is the healthiest part. Who the hell came up with that? It’s so obvious that bread crust has the exact same ingredients as the rest of the bread. It’s not like someone took a glob of dough and wrapped it in some other “crustifying” substance. It’s the same stuff, just oxidized and hardened a bit more by the scalding heat of the oven. In fact, perhaps the only difference between crust and everything else is that if the crust weren’t there, there’d be nothing protecting the rest of the loaf from becoming…crust.

My point is, crust is not the slightest bit healthier for you than the rest of the bread, and yet I went a significant portion of my young life believing that it was. Given that, just how much of what I know about the way the world works can be attributed to pseudo-facts that I’ve just never thought to consciously doubt?

I was a student at UCLA when they started widening the 405. I lived on the west side at the time, and I suffered through the abominable traffic, closed roads, and chaotic construction messes in the name of improving people’s commutes and making it easier to get around Los Angeles. At the time, I had no qualms about the work being done—I truly believed it would help. The possibility that the solution might have been the wrong one never even crossed my mind, because I believed that anyone in charge of spending a billion dollars must know a lot more about the situation than I do. For lack of a better expression, I was eating the crust.

Just because a solution is intuitive, that doesn’t mean it’s right.

I developed an interest in urban planning before the 405 project finished. My interest led to some light research, and my research led me to a dreadful conclusion: The widening project wasn’t going to have any effect on traffic at all. Years later, it turns out I was right. Widening the freeway was the intuitive solution, but that didn’t make it the right one.

I think the reason our intuition performs so poorly in the field of urban planning is that we tend examine the inputs to a problem as though they’re static. Looking at traffic on the 405, planners recognized that the road’s capacity didn’t meet the demand and therefor proposed increasing the road’s capacity to compensate. In doing so though, they completely ignored the possibility that the inputs to the problem, in this case demand for and supply of road, might be interrelated.

As it turns out, they are. The function that defines the demand for road space depends on the road capacity. This can actually be explained by a theory called “Induced demand,” which more or less suggests that when a highway is expanded, driving becomes easier and more desirable, which in turn causes more people to want to drive. Simply put, changing the capacity changes the demand. Now, the fact that the two inputs are dependent on each other wouldn’t be such a bad thing if they were negatively correlated. In that case, we would find that increasing road capacity would cause less people to want to drive, and that would be totally fine, but that’s not the case here. When it comes to driving, more roads creates more desire for road, and as a result, despite what our intuition may lead us to believe, the problem in its current form is unsolvable.

It goes without saying that any supply problem in which the demand is positively correlated to the supply is similarly unsolvable. Take parking for instance. Since the dawn of the automobile, our solution to the lack of parking has been to build more of it. We’ve been doing it for almost a hundred years, and our parking supply during that time has increased exponentially. But despite all the effort, you’d be farfetched to name a time in which parking really wasn’t a problem. (Unless of course you include the brief period in the early 20th century where cars were mostly unaffordable to the working class, but that’s the subject of another article.)

Turns out it’s the exact same situation. When you build more parking, the number of people looking for parking spots doesn’t stay the same. If it did, the solution would make sense, but what actually happens is that the additional parking spots create an additional incentive to drive, which subsequently increases the number of people looking for parking spaces and causes the extra spots to fill up.

Imagine you got invited to a party at your friend’s house a few miles away from where you live. Your friend lives in an area that you know has limited parking, and you’ve spent time circling the block for a spot in his neighborhood before. When the time comes to head out, you consider your transportation options:

  • Train | The train isn’t bad, but the stop is a few blocks away and you don’t feel like walking.
  • Bike | Biking is fine, but it take about 10 minutes longer than driving does, and you have to put a little work into it.
  • Drive | Convenient and clearly the shortest travel time, but parking is going to suck.

Given your options, you’re likely to either bike or take the train, since the annoyance of parking and risk of getting ticketed are a big deterrence to driving. The parking situation in the neighborhood remains unchanged.

Now imagine your friend lives in a brand new apartment complex stocked with plenty of extra, guest parking. When the time comes to head out, you once again consider your options:

  • Train | Same as above.
  • Bike | Same as above.
  • Drive | Clearly the fastest option, and also highly convenient.

Let’s face it: you’re probably going to drive. And it won’t just be you either. Any time anyone visits that complex for any reason, they’re going to make the same choice you did, knowing that it’s the most convenient one. And if there’s really a lot of parking, the building tenants are going to start thinking about that second car they’ve always wanted.

“Hell, I have a place to put it, so why not?”

With all those people choosing to drive when they normally wouldn’t have, the number of cars in the area skyrockets, going up and up until… the parking runs out. At that point, driving again becomes inconvenient, and people start opting for alternative forms of transportation. Meanwhile, available parking in the area is again at maximum capacity, exactly as it was in the case where no additional parking had been built at all. Net gain: nothing.

You may be tempted to make the argument that the pool of people with cars looking for parking is not infinite, and that as we build more and more parking, the demand for parking spots must eventually start to go down, but again, that theory collapses due to the fact that even the number of car owners isn’t fixed. Excessive supply of parking will simply convert non-car owners into car owners and single car owners into multiple car owners until the supply runs out.

Despite all of this, you’d be amazed how often you’ll hear frustrated residents at neighborhood planning meetings demanding that property developers add as much parking as possible to their developments in order to prevent a parking problem. If lack of parking was really their concern, what they should be asking for is the exact opposite! If you build an apartment complex that has an abundance of available parking spots, guess who’s going to move in: people who own cars.

We as a community should acknowledge our susceptibility toward believing things that aren’t true, just because we’ve never been taught to doubt them. When we make decisions based purely on instinct and observation, we subject ourselves to the possibility of making expensive and irreversible mistakes that may otherwise have been avoidable. No one ever makes a decision knowing that it’s the wrong one. But wrong decisions still get made. If we acknowledge that fact, we can compensate for it in our process by challenging each other’s assumptions and encouraging all decisions, no matter how obviously correct they seem, to be backed by research and fact. And only then will we all be able to eat our crust-free PB&J’s in peace.

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