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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And what does that tell us about driverless cars?

Posted by jimvb | Report as abusive

The problem is, no matter how much you maneuver in freeway traffic, the stop lights you eventually hit after you get off the freeway are spaced such that the meager gains you’ve attained are now lost or otherwise minimized.

On surface roads, you reach a similar issue, when you hit a left-turn light, which is usually finicky about how late you can hit the sensor before it throws you off to the next cycle. You could distance yourself by two blocks, but hit the left-turn in-ground sensor too late and the cars two blocks behind you will now catch up with you.

Posted by GRRR | Report as abusive

I think you got it wrong. The real utility is spending as little time as possible in traffic. The happiness you get from switching lanes and driving through side streets is because “doing something” is your mental proxy for “moving towards my goal faster”. But it’s a bad proxy.

Your conclusion is “don’t talk to an economist, talk to a behavioral economist”. But I think what you should do is talk to an engineer instead.

Posted by Gidi_A | Report as abusive

This is exactly why I cycle to work each day. I might not actually get home any faster, but it sure feels like I do. I’m much happier making progress at 12-15 mph on my bike than not making progress at 0 mph in my car before a quick burst of 30-40 mph.

Posted by MitchW | Report as abusive

This is exactly why I cycle to work each day. I might not actually get home any faster, but it sure feels like I do. I’m much happier making progress at 12-15 mph on my bike than not making progress at 0 mph in my car before a quick burst of 30-40 mph.

Posted by MitchW | Report as abusive

You sit in comfortable chair, perform some trivial steering and control functions, and listen if you like to your choice of a nearly infinite variety of music, books on tape, or other aural input. Life for the 21st Century commuter is certainly nasty and brutish; no wonder the scheming to speed it up by a few percentage points.

Posted by KenWis | Report as abusive

I’ve come upon a more interesting and galling phenomenon. Here on the winding, hilly roads of western New York, the speed limit on a State Route is 55 mph. The state offers a passing lane on particularly steep hills, because the heavy trucks will struggle to be at 30 mph half-way to the top.
I’ll find myself five full miles stuck behind a car going 50, unable to pass, and when the hill with now two lanes offers me the chance, that car in front is 75% sure to accelerate to 55 or 60, and liable to make me pass on the right. If then I fail to pass, when the two lanes become one again, the loafer invariably dials back down to 50 mph. Americans. Can’t live with ‘em…

Posted by parabull | Report as abusive

In his book The Rise of American Air Power, historian Michael Sherry relates that morale surveys of fighter pilots and bomber pilots revealed that fighter pilots tended to be more positive about their jobs, even though their mortality rates were higher. But because they didn’t have to essentially fly in a straight line and draw flak, they FELT like they were more in control of their lives and destinies, and this was a stronger determinant of their job satisfaction than the actual odds of getting shot down.

Posted by askpang | Report as abusive

So does the aggregate private utility gain exceed the negative externalities (slower traffic, higher accident rate) generated by lane-switching ?

What are the implications for autonomous vehicles? Will this pro-agency preference depress demand for self-driving cars?

Posted by rpenm | Report as abusive

Re. negative externalities from the rational choice

Collective collisions – in tunnels, etc. where drivers do not have agency to switch lanes…

Posted by A-V | Report as abusive

Ever watch people repeatedly pushing the pedestrian walk button or the elevator call button? Lots of people cannot stand still and do nothing – even when there is nothing that they can do.

Posted by walstir | Report as abusive

“I’ll find myself five full miles stuck behind a car going 50″

I bet you tail them uncomfortably close. That’s a pretty sure way of causing somebody to slow down 5-10 mph.

Posted by TFF17 | Report as abusive

“All of humanity’s problems stem from man’s inability to sit quietly ….”

-Blaise Pascal, Pensee’s

Posted by Publius | Report as abusive

There’s also some positive reinforcement at work. Just like at the casino, where every once in a while the bet pays off, changing lanes helps once in a while, sometimes by quite a lot (if the accident is in fact in the lane you’re sitting in). So when weighing whether to change lanes, you have to consider the possibility that this could be that rare instance where changing lanes will actually help. Of course, you’ve probably got equally good odds that the accident is in some other lane, but it seems we remember the times when our bet payed off and forget when it didn’t.

Posted by Sanity-Monger | Report as abusive

I agree with Felix’s point about preferring to keep moving as well as Sanity-Monger’s point about reinforcement, which I’d extend more broadly.

It’s not surprising that human nature defaults to “get there faster by moving into the faster lane” because that is generally the correct decision-making process when in in free-flowing, non-congested traffic. Stuck behind a left-turner? Hop over a lane to the right and go around them. Behind someone going 5 mph under the speed limit? Pass them and then get back in the same lane if need be. Congestion changes that situation, but people’s minds are conditioned to follow the more intuitive path of keeping moving, which does tend to work when traffic isn’t congested.

Posted by realist50 | Report as abusive

All hail Lord Dopamine!

Posted by squarecat | Report as abusive