The law of unintended consequences

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People are complicated. Life is complicated. Ecosystems are complicated. And despite our best efforts or intentions, we have a remarkable history of messing things up in unexpected ways.

One simple theory for why this may be is that unintended consequences are likely to happen whenever we try to regulate a complex system by using a simple system. This so often happens in any kind of large-scale or government attempt to control something within a complex system using relatively simple programs, regulations, laws, policies or other actions. Things will happen that we didn’t anticipate.

Examples of the Law of Unintended Consequences

Examples abound:

A policy of suppressing forest fires that goes on to cause even greater fires.
An attempt to reduce traffic in Bogotá by restricting who could drive each day based on licence plates that led people to simply buy more cars.
More open workplaces that cause people to behave more privately: the transparency paradox.
Elimination of predators that leads to the proliferation of grazing animals and a reduction in diversity.
The effects of literally any dam built anywhere.
What happens when you change software.
Desire paths
The Streisand effect
The Diderot effect
Or social distancing policies that results in outdoor natural spaces being crammed with people at weekends.
And on, and on.

The traffic example in Bogotá is from the Freakonomics podcast episode on the cobra effect. The workplace privacy example is known as the transparency paradox.

Related Ideas to the Law of Unintended Consequences

Often, as with some of these, the outcome can be the opposite of what you intended, known as the cobra effect. Controlling complex systems is difficult.
Goodhart's Law
Campbell's Law
You Get What You Measure
Conway's Law
The Law of Diminishing Returns

Published 3 May 2020

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Congested Equilibrium

Unknown Unknowns

The Cobra Effect

Pollution is highly localized: take the back streets

Goodhart's law illustration showing a manager frustrated by 1000's of tiny nails when measuring on number of nails made, and pulling their hair out when presented with giant nails when measuring on weight

Goodhart’s Law: when a measure becomes a target, it ceases to be a good measure.

Jevon’s Paradox

You, like me, probably dislike being stuck in traffic. If you live in a densely populated area, it's likely that for at least some of the day, a number of the major roads around you are congested, i.e. there's a lot of traffic, and it tends to go slowly. Unfortunately, as I learned with the phrase "Congested equilibrium," from UCL Professor David Metz, there's no magic wand to wave for roads that will run smoothly and get you to your destination with minimal hassle. What is Congested Equilibrium? It's easy to assume that there's a fixed amount of traffic on the roads. So if your local road agency widens, improves, or adds alternative fast roads to get to your destination, you might think that traffic will improve. And it does, but only briefly. Then somehow the traffic jams return. The reality is that in densely populated areas, traffic congestion tends to be self-regulating. When driving is slow and somewhat painful, people who would have driven make other choices: choose not to travel—maybe a video call instead, or just don't go to the shops take a different means of transport such as a train or bike travel earlier or later take different routes After millions in road investment—perhaps widening roads or building a bypass or extended stretch of motorway—traffic runs faster, for a time. But when people realise that roads are again a good option for travel, some of those who had chosen not to drive or didn't use that route before, jump back in the car and make use of the new, improved roads. And the increased traffic once again leads to congestion that gets progressively worse until people decide to make other choices once again. Traffic congestion is a feature of road networks that is very hard to avoid because densely populated areas have a vast reserve of these suppressed trips—people who would drive if the traffic was better—ready to make use of an improved road network when it arrives. From congested equilibrium comes the maxim in travel planning circles: "You can't build your way out of congestion." I learned about congested equilibrium and the general trials and challenges of travel planners in the book Good to go? Decarbonising Travel After the Pandemic by Professor David Metz. Although the book had less to do with decarbonising than I expected, it did teach me a great deal about the challenges and considerations of travel planning. Related Ideas to Congested Equilibrium Marchetti's Constant—as we travelled faster, we travelled farther, maintaining about an hour's daily travel time Laws of Expansion Isochrones Pollution is highly localized: take the back streets Travel choices in London Our Senses are Built to Take in Information at Human Pace Jevons paradox Cobra effect Frequency is freedom, a line from Jarrett Walker about the impact of frequency on public transport. I haven't sketched this yet, but it's so catchy I thought I'd share More I learned About Traffic For the last half a century or so, the average daily travel time has remained unchanged. This is despite huge investments in road networks in urban areas. When I find myself stuck in and complaining about traffic, my mind flashes back to a memory of a billboard in San Francisco that read, "You are not stuck in traffic. You are traffic." Then I feel better about my fellow drivers. What people like least is uncertainty about journey time. So digital navigation, as exemplified by Google Maps, is doing an amazing job at giving us peace of mind here. Until ChatGPT, I put Google Maps as the best app out there. In European cities you tend to find either high public transport use (like London), or a lot of cycling (think Copenhagen). But you don't tend to find high levels of both. Copenhagen's proportion of car journeys is similar to London's. The car has an appeal when the roads allow it. Improving cycling tends to pull people from public transport and vice versa rather than pull people from their cars. Of David Metz' points that stick with me is also that the most effective way to reduce car usage in city centres, in conjunction with improving other means of travel, is to reduce the availability of parking. Also, each city is different: some cities like London are spread wide and the distances are large, some have more cooperative weather, some have a lot of hills, and some are in countries where cars are a significant status symbol. There's no one-size-fits-all.You, like me, probably dislike being stuck in traffic. If you live in a densely populated area, it's likely that for at least some of the day, a number of the major roads around you are congested, i.e. there's a lot of traffic, and it tends to go slowly. Unfortunately, as I learned with the phrase "Congested equilibrium," from UCL Professor David Metz, there's no magic wand to wave for roads that will run smoothly and get you to your destination with minimal hassle. What is Congested Equilibrium? It's easy to assume that there's a fixed amount of traffic on the roads. So if your local road agency widens, improves, or adds alternative fast roads to get to your destination, you might think that traffic will improve. And it does, but only briefly. Then somehow the traffic jams return. The reality is that in densely populated areas, traffic congestion tends to be self-regulating. When driving is slow and somewhat painful, people who would have driven make other choices: choose not to travel—maybe a video call instead, or just don't go to the shops take a different means of transport such as a train or bike travel earlier or later take different routes After millions in road investment—perhaps widening roads or building a bypass or extended stretch of motorway—traffic runs faster, for a time. But when people realise that roads are again a good option for travel, some of those who had chosen not to drive or didn't use that route before, jump back in the car and make use of the new, improved roads. And the increased traffic once again leads to congestion that gets progressively worse until people decide to make other choices once again. Traffic congestion is a feature of road networks that is very hard to avoid because densely populated areas have a vast reserve of these suppressed trips—people who would drive if the traffic was better—ready to make use of an improved road network when it arrives. From congested equilibrium comes the maxim in travel planning circles: "You can't build your way out of congestion." I learned about congested equilibrium and the general trials and challenges of travel planners in the book Good to go? Decarbonising Travel After the Pandemic by Professor David Metz. Although the book had less to do with decarbonising than I expected, it did teach me a great deal about the challenges and considerations of travel planning. Related Ideas to Congested Equilibrium Marchetti's Constant—as we travelled faster, we travelled farther, maintaining about an hour's daily travel time Laws of Expansion Isochrones Pollution is highly localized: take the back streets Travel choices in London Our Senses are Built to Take in Information at Human Pace Jevons paradox Cobra effect Frequency is freedom, a line from Jarrett Walker about the impact of frequency on public transport. I haven't sketched this yet, but it's so catchy I thought I'd share More I learned About Traffic For the last half a century or so, the average daily travel time has remained unchanged. This is despite huge investments in road networks in urban areas. When I find myself stuck in and complaining about traffic, my mind flashes back to a memory of a billboard in San Francisco that read, "You are not stuck in traffic. You are traffic." Then I feel better about my fellow drivers. What people like least is uncertainty about journey time. So digital navigation, as exemplified by Google Maps, is doing an amazing job at giving us peace of mind here. Until ChatGPT, I put Google Maps as the best app out there. In European cities you tend to find either high public transport use (like London), or a lot of cycling (think Copenhagen). But you don't tend to find high levels of both. Copenhagen's proportion of car journeys is similar to London's. The car has an appeal when the roads allow it. Improving cycling tends to pull people from public transport and vice versa rather than pull people from their cars. Of David Metz' points that stick with me is also that the most effective way to reduce car usage in city centres, in conjunction with improving other means of travel, is to reduce the availability of parking. Also, each city is different: some cities like London are spread wide and the distances are large, some have more cooperative weather, some have a lot of hills, and some are in countries where cars are a significant status symbol. There's no one-size-fits-all.

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