Congested Equilibrium

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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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In a 2002 Pentagon briefing, then U.S. Secretary of Defense Donald Rumsfeld famously said: "Reports that say something hasn't happened are interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say, we know there are some things we do not know. But there are also unknown unknowns — the ones we don't know we don't know. And if one looks throughout the history of our country and other free countries, it is the latter category that tends to be the difficult ones." It wasn't typical media material. It even won Rumsfeld the "Foot in Mouth" award from the Plain English Campaign in 2003. But the idea of unknown unknowns has endured. Awareness—Understanding examples When placed in a 2x2, somewhat like I have done, some people have referred to it as the Rumsfeld Matrix (although he didn't invent it), or the Awareness—Understanding Matrix. I prefer diving straight into Unknown Unknowns as they're the crux of it. For example: Say you find out you're going to have a baby. There's a lot you know and a lot you know you don't: Unknown Knowns — things you know that people know about being a parent and having a baby, but you just don't know them yet. Doing your research and homework transforms these into Known Knowns. Known Knowns are the things you already know (or just learned) you'll need to do when you're a parent. Your baby will need feeding and changing, clothes, a place to sleep etc. You plan for these, you buy clothes, a crib, and learn about breastfeeding or the bottle. Known Unknowns — Things like the baby's gender, or whether they'll arrive early or late. You know you don't know these yet, but you can make a plan either way. Finally, there are Unknown Unknowns — which, in this case, could be that, despite all your plans, you find yourself with twins. Or, say you plan to start a café: Unknown Knowns What you know is knowable, but you don't know it, yet You can find data on the market, the costs, and potential customers. These things can be known through research—others know them—but you didn't know them. Known Knowns What you know you know Your costs, your product, your route to market, everything you learned in your research. You make your plan around these. Known Unknowns What you know you don't know How people will respond to your product, how fast sales will be, and whether your rent will change. Unknown Unknowns What you didn't know you didn't know Just as you launch your café, Starbucks moves in next door, or we hit a global pandemic. It's what you don't know, that you don't know, that gets you. After all, if you knew it, you'd have prepared for it. He Who Knows There's a well-known saying called "He who knows" which relates to Unknown Unknowns: He who knows not, and knows not he knows not, is a fool; shun him. He who knows not, and knows he knows not, is simple; teach him. He who knows, and knows not he knows, is asleep; awaken him. He who knows, and knows he knows, is wise; follow him. Note that, like most interpretations of the Awareness/Knowledge-understanding framework, Unknown Knowns is interpreted as things you know but don't know you know. These might be implicit knowledge that you are yet to make a connection with. Related Ideas to Unknown Unknowns We have a host of sayings and thoughts that relate to this. Nassim Nicholas Taleb's Black Swan events: if every swan you've ever seen is white, it's easy to assume that all swans are white, but the next one you see could be black. The Lucretius problem, also from Taleb: We tend to believe the biggest event we've seen is the biggest that could happen. For example, we test our financial models against the most significant market crashes, but each was bigger than any that had hit before. In theory, practice is the same as theory, but not in practice. No plan survives contact with the enemy — from Prussian Field Marshal Helmuth von Moltke the Elder Whatever our plans, or what we think we know, or even what we think we know we don't know, we must adapt to succeed. Unknown unknowns evidently weigh heavily on me, as I seem to have drawn many more related ideas: Black Swan events The Lucretius Problem The Johari Window — for self-knowledge The Conscious Competence framework In theory, practice is the same as theory, but not in practice VUCA - Volatility, Uncertainty, Complexity, Ambiguity OODA Loop - Observe, Orient, Decide, Act, Repeat On mistakes Hindsight bias — everything is obvious after the fact Physics Envy Hofstadter's Law The Cobra Effect The Law of Unintended Consequences Do a 2x2 MatrixIn a 2002 Pentagon briefing, then U.S. Secretary of Defense Donald Rumsfeld famously said: "Reports that say something hasn't happened are interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say, we know there are some things we do not know. But there are also unknown unknowns — the ones we don't know we don't know. And if one looks throughout the history of our country and other free countries, it is the latter category that tends to be the difficult ones." It wasn't typical media material. It even won Rumsfeld the "Foot in Mouth" award from the Plain English Campaign in 2003. But the idea of unknown unknowns has endured. Awareness—Understanding examples When placed in a 2x2, somewhat like I have done, some people have referred to it as the Rumsfeld Matrix (although he didn't invent it), or the Awareness—Understanding Matrix. I prefer diving straight into Unknown Unknowns as they're the crux of it. For example: Say you find out you're going to have a baby. There's a lot you know and a lot you know you don't: Unknown Knowns — things you know that people know about being a parent and having a baby, but you just don't know them yet. Doing your research and homework transforms these into Known Knowns. Known Knowns are the things you already know (or just learned) you'll need to do when you're a parent. Your baby will need feeding and changing, clothes, a place to sleep etc. You plan for these, you buy clothes, a crib, and learn about breastfeeding or the bottle. Known Unknowns — Things like the baby's gender, or whether they'll arrive early or late. You know you don't know these yet, but you can make a plan either way. Finally, there are Unknown Unknowns — which, in this case, could be that, despite all your plans, you find yourself with twins. Or, say you plan to start a café: Unknown Knowns What you know is knowable, but you don't know it, yet You can find data on the market, the costs, and potential customers. These things can be known through research—others know them—but you didn't know them. Known Knowns What you know you know Your costs, your product, your route to market, everything you learned in your research. You make your plan around these. Known Unknowns What you know you don't know How people will respond to your product, how fast sales will be, and whether your rent will change. Unknown Unknowns What you didn't know you didn't know Just as you launch your café, Starbucks moves in next door, or we hit a global pandemic. It's what you don't know, that you don't know, that gets you. After all, if you knew it, you'd have prepared for it. He Who Knows There's a well-known saying called "He who knows" which relates to Unknown Unknowns: He who knows not, and knows not he knows not, is a fool; shun him. He who knows not, and knows he knows not, is simple; teach him. He who knows, and knows not he knows, is asleep; awaken him. He who knows, and knows he knows, is wise; follow him. Note that, like most interpretations of the Awareness/Knowledge-understanding framework, Unknown Knowns is interpreted as things you know but don't know you know. These might be implicit knowledge that you are yet to make a connection with. Related Ideas to Unknown Unknowns We have a host of sayings and thoughts that relate to this. Nassim Nicholas Taleb's Black Swan events: if every swan you've ever seen is white, it's easy to assume that all swans are white, but the next one you see could be black. The Lucretius problem, also from Taleb: We tend to believe the biggest event we've seen is the biggest that could happen. For example, we test our financial models against the most significant market crashes, but each was bigger than any that had hit before. In theory, practice is the same as theory, but not in practice. No plan survives contact with the enemy — from Prussian Field Marshal Helmuth von Moltke the Elder Whatever our plans, or what we think we know, or even what we think we know we don't know, we must adapt to succeed. Unknown unknowns evidently weigh heavily on me, as I seem to have drawn many more related ideas: Black Swan events The Lucretius Problem The Johari Window — for self-knowledge The Conscious Competence framework In theory, practice is the same as theory, but not in practice VUCA - Volatility, Uncertainty, Complexity, Ambiguity OODA Loop - Observe, Orient, Decide, Act, Repeat On mistakes Hindsight bias — everything is obvious after the fact Physics Envy Hofstadter's Law The Cobra Effect The Law of Unintended Consequences Do a 2x2 Matrix

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