(credit: Gary J. Wood)

Rules vs instincts

Economic and social forces condition our behaviour in traffic — not always for the best

“Get out of my way!” If you’re a driver, this phrase has probably crossed your lips (and if not actually said aloud, then most likely crossed your mind) at some point, and maybe more than once. It may just look like a matter of speech, but the use of the possessive pronoun implies that we — even just a little bit — consider the way in front of us ‘ours’.

One reason is that road space is scarce. When two drivers simultaneously attempt to occupy the same piece of road, it usually doesn’t end well. So it is not surprising that we claim bits of the road as ours. And where you have scarce resources and property rights, you see economic transactions and behaviour.

Governments or private operators may charge drivers for the right to use particular roads, but the economics of road use goes well beyond tolls and congestion charges. We don’t ‘buy’ and ‘sell’ particular sections of the highway to each other, but that doesn’t mean we don’t use mechanisms to facilitate the smooth and effective exchange with others of scarce road space.

Most countries have traffic codes that set out the rules and define the instruments that do much of the heavy lifting. Vehicles are supposed to be driven on a particular side of the road. Traffic lights allocate ownership of the road at an intersection to a particular traffic stream, preventing others from claiming it simultaneously. Give way arrangements can use signs, markings on the road, or even default rules (like the priority to the right in many European countries), but they all grant priority status to some road users when it comes to claiming ownership.

Such lights, signs and rules are a great help. Without them traffic could be a lot more challenging, maybe something like this:

But traffic codes are not the whole story. Drivers leaving a roadside parking space, for example, are supposed to defer to the higher-status traffic, but at busy times it may take a long time before there is a sufficiently large gap for them to do so. People without infinite patience might therefore need to negotiate: signal their intention and hope that someone will let them in. This usually happens before long — not all drivers claim the priority they are entitled to.

In some places drivers behave very assertively, signalling their intent by squeezing into a narrow gap and effectively forcing the driver behind to hold back. If that is part of the social norms, this can work very well. Elsewhere social norms may be built on courtesy: if you’re on a busy road and see a parked driver using his indicators, you just let them in.

In either case, the lower-status driver has got little to offer other than a smile, a wave, or a couple of blinks of the hazard lights. How come such exchanges happen all the time? Reciprocity could be one explanation: you do it for one driver today, someone might do it for you tomorrow. Maybe fairness plays a part, too. It does feel kind of unfair for someone to be waiting forever, and that might encourage many higher-status drivers to give up their ownership right. Yet not everyone does so — perhaps that is an instance of the bystander effect: we are in a hurry, but surely someone behind us will be able to afford the minor delay.

Regardless, we see how de facto, informal customs can augment the general rules and deliver greater efficiency. Whether the behaviour of a driver is guided by courtesy, pity, or simply by adherence to the prevailing social norms, the few seconds lost is quite small in comparison to the gain of the lower-status driver, and so the driving community ends up better off.

But sometimes social norms, rules and efficiency are not so well aligned. When a road with multiple lanes narrows down and the traffic needs to squeeze into a reduced number of lanes, there are two ways drivers can respond. They can merge early, as soon as the bottleneck in announced; or they can merge late, close to point of confluence.

According to the US Federal Highway Administration, if the traffic is free flowing, merging early is preferred by the traffic engineering community, while late merging is better when traffic is slow, with few or no gaps. That view is echoed elsewhere too, like in the UK and in Belgium. But not every jurisdiction has explicit rules, and even if there is signage, it often has a hard time combating the conflicting moral instincts of the drivers.

The fundamental problem is that, as soon as a sufficiently large number of them decides that merging early is morally the right thing, social conformity bias makes the ideal situation — two parallel traffic queues of the same length merging in turn at the bottleneck — impossible. Anyone wishing to do the right thing from an efficiency viewpoint will be seen as a cheat. The pressure for the others to conform is overwhelming, even without busybody drivers who feel it is their duty to actively prevent whizzing past by straddling both lanes.

“What does ‘use both lanes’ mean anyway?”

Before long, everyone except the odd antisocial barbarian is queuing in a single lane. Signs telling drivers to “use both lanes” are too vague to be much use: do they really mean all the way?

The phenomenon of cutting in at the last moment is right up Freakonomics’ alley. When this very topic arose, economist Steven Levitt told his co-author Stephen Dubner that he does not (or at least no longer) engage in this practice. Despite the clear efficiency gains of late merging (and despite the fact that by merging early, he contributes to the problem), he is “not that kind of person”. However, he also decried the poor signage that confounds the conflict between morals and efficiency. A sign that read something like “Lanes merging in 1 mile. Stay in lane” would be much better, an authoritative and unambiguous nudge for drivers.

Of course, nothing stops you trying out your own solution. In writing “Why not?”, Ian Ayres and Barry Nalebuff came up with an ingenious approach. Instead of zooming past the inside lane’s slow-moving traffic, simply track the speed of the last vehicle in the queue. Yes, there’s free road space ahead of you, but as you advance it fills up behind you, and by the time you reach the bottleneck, the perfect conditions for late merging are a fact. You may get some angry light flashing and tooting behind you, but hey, doing your civic duty doesn’t come easy. And those are jerks anyway.

“But I was in the right!” (image: cygnus921)

Ayers and Nalebuff discarded the idea, but in any case, it is much better than what I once witnessed in — where else — the capital of my native country. Rush hour meant traffic was bumper to bumper in two lanes at the point where one lane was blocked by road works. The alternating zipper approach worked well until, just ahead of me, a misunderstanding arose between two drivers in the adjacent lanes with respect to who was entitled to go next through the bottleneck. What happened next was the slowest collision I ever saw. Neither driver wanted to give in, and inescapably the bodies of both cars touched, first gently, then squeezing harder and harder, as if they were lovers, but with the sound of crushing metal.

For some people, a bent car is a price worth paying when you are convinced you are in the right. Remember this when you’re next on the road. Have a safe journey.

Originally published at koenfucius.wordpress.com on April 13, 2018.

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Accidental behavioural economist in search of wisdom. Uses insights from (behavioural) economics in organization development. On Twitter as @koenfucius

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