The utility of switching lanes

By Felix Salmon
April 11, 2014

Josiah Neeley has an evil, hour-long commute. But unlike most of us with traffic issues, he actually decided to do something constructive with it: according to the flip of a coin, he either commutes normally, switching lanes when doing so seems sensible, or else sticking religiously to the left-hand lane and just sweating it out, no matter how fast or slow it goes.

Neeley doesn’t have a statistically significant result yet, but initial indications are pretty much what you might expect, if you understand the psychology of traffic: if you just sit in a single lane, you spend no more time in traffic than if you aggressively switch lanes and try to go as fast as possible at all times.

There are two possible conclusions to draw from this. The first is that, rationally, no one should switch lanes when they’re stuck in traffic. It doesn’t make them get to where they’re going any faster, but it does slow down the road as a whole.

The second, however, is the exact opposite. As Neeley says:

The hardest part of the experiment is just sticking to it. When it’s a left hand lane only day, it’s often quite difficult to keep to the plan when my lane is going forward at a crawl. But then I remind myself that this is for Science, and I soldier on. Perhaps more importantly, I’ve noticed that my subjective sense of how bad the traffic is on a particular day doesn’t necessarily line up with the objective data. On many a day I feel like my drive has gone on forever, only to find that it wasn’t any longer than on previous days where it felt like I was flying down the highway.

This is important: the really painful part of being stuck in traffic is not, really, the actual amount of time that it takes to get from Point A to Point B. Rather, it’s the “stuck” bit. As a result, the best way to minimize the suffering involved in a long commute is not, necessarily, to simply get to your destination as fast as you possibly can.

One of my lesser-value skills is that when my wife and I are stuck in highway traffic, and she’s driving, I’m quite good at looking at the live traffic maps, from Google and Apple, and finding a way to use surface streets to skip forward a couple of exits. My guess is that 90% of the time, when we do that, we don’t actually save time. But pretty much 100% of the time we both end up significantly happier than we were when we were crawling up the freeway. If you go a longer distance at a modest speed, but you’re not stuck in traffic on an ugly highway, you feel as though you’re getting somewhere.

The same is true when you stay on the highway, rather than leave it: the act of changing lanes, and thereby briefly overtaking the car which up until a moment ago was in front of you, makes you significantly happier than just sitting there like a passive schmuck. Which is why we all do it.

In other words, if you want to understand utility functions, don’t talk to an economist. The economist will find a proxy for utility — in this case, time — and then try to work out what kind of behavior optimizes for the proxy. If Neeley had discovered that changing lanes frequently only served to cause a significant increase in time spent commuting, he would probably just opt to sit in a single lane henceforth, even when doing so was difficult, and even when doing so increased the number of days where it felt like his drive had gone on forever.

The more interesting experiment, I think, would be to judge not actual time spent commuting, but some kind of subjective measure (say, on a four point scale) of how brutal the commute was that day. The important thing isn’t whether you shave a minute here or there: it’s how you feel once you get to your destination. This is something I’ve noticed since switching almost exclusively to Citibike when I bike around New York — while the Citibikes are undoubtedly slower than my regular bike, that doesn’t make me more impatient in traffic. Quite the opposite, indeed: I feel as though I’ve become a more zen biker as a result of the switch.

If you look at subjective rather than objective measures, I’m pretty sure that all our lane switching will turn out to have a useful purpose after all: it makes us feel as though we’re in control of our own destiny. Which, ultimately, is more important than an extra minute’s commute.

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