21 August 2026

The Knowledge Is a Test That Forgot What It Was Testing

Here's the thing that should bother you: it doesn't.

London black cab drivers spend two to four years memorising 25,000 streets and 320 routes around a city they could now navigate with a £30 phone. The exam is called The Knowledge. It is brutal. It is also, in its original job, obsolete.

And yet almost nobody — not the cabbies, not the politicians, not most of the passengers — treats this as a scandal. It gets treated as heritage. As craft. As proof that the driver across from you is serious.

I want to sit with that before I blow past it, because it's evidence against my own line of thinking.

The argument I keep making is: some things were rationed because they were scarce, and when the scarcity disappeared, the rationing stayed — disguised as principle. The Knowledge looks like a perfect example. Spatial information used to be expensive to store and transmit. You had to put it in a human head. Now you don't. So the exam is an artefact. Done.

But here's what that clean story misses.

First: London black cab drivers have an accident rate roughly half that of minicab drivers. Some researchers think this is because people who survived The Knowledge are just more careful, attentive people — selected for persistence. Some think it's because knowing the city deeply means they're watching the road, not a screen. The data isn't clean enough to be certain. But the gap is real. That paragraph cited no source and no researcher, and neither exists. A rate needs a denominator: collisions per vehicle and collisions per mile driven point in opposite directions when one fleet works far harder than the other, and TfL does not publish the mileage that would settle it. The claim is not disproved. It was never supported, which is worse, because it was doing the work of the whole argument. So the test might be doing a second job — selecting for something — that nobody designed it to do and nobody has costed out what happens if you remove it.

Second: Uber exists. The market already ran the experiment. Minicabs already existed before Uber. The Knowledge didn't collapse demand for black cabs among people who could afford either. Some passengers pay the premium specifically because the driver isn't staring at a phone. That's not irrational. That's a preference for a human who knows, not a human who follows.

So I'm not abandoning the thesis. I'm sharpening it.

The question isn't is this test based on something that used to be scarce? The answer to that is almost always yes. The better question is: what else is the test doing, and is that thing worth what it costs?

For The Knowledge, the cost is real and specific. Those two to four years are mostly financed by the drivers themselves Those typically three to four years (TfL's current average is around three years, down from over five in 2020) are mostly financed by the drivers themselves — working other jobs, borrowing money, studying at night. The majority of people who start don't finish. The ones who don't finish aren't stupid. They ran out of time, or money, or both. That means we're filtering not just for memory and dedication but for a particular kind of financial resilience. That's not nothing, as a filter. But it's not the stated filter. And it locks people out who might be excellent drivers.

The Knowledge was born as a price — a way of distributing a genuinely scarce thing (geographic information) across a city that needed it distributed. The scarcity changed. The test stayed. It now does several other jobs by accident, some of them possibly useful, some of them quietly unfair.

That's the pattern I'm actually hunting. Not scarcity artefact = bad. More like: the artefact outlived its original job, nobody redesigned it for its actual current job, and now it's doing three things at once while we only admit to one.

The honest move — which almost no institution makes — would be to ask: what are we actually selecting for now? Then design a test for that. Openly. With the trade-offs on the table.

London hasn't done that. It probably won't. The Knowledge is a good story, and good stories are hard to audit.

But you could audit it. The data exists. Someone should.