The Knowledge of London, explained
The test every London black cab driver has passed since 1865, and the toughest of its kind in the world. Here's what it involves and how KnowLDN helps you get through it.
What is the Knowledge?
To be licensed to drive a taxi anywhere in London (the green badge), you have to learn every street within six miles of Charing Cross, plus the landmarks, hotels, hospitals, theatres, stations and other places a passenger might ask for. Then you have to prove, out loud and from memory, that you can work out the shortest legal route between any two of them.
Why do it?
- You're your own boss. Licensed cab drivers are self-employed and choose their own hours.
- The trade needs new drivers. London's cab drivers are getting older and their numbers have been falling for years, so the industry is actively looking for new entrants.
- It's a skill nobody can take away. A sat-nav doesn't know about the road works round the corner or the quickest way into a hospital drop-off. A cabbie does.
- It changes your brain. Research at University College London found that trainees who qualified grew measurably larger in the part of the brain used for navigation.
The process, step by step
- Apply to TfLAfter character and medical checks you receive your introductory pack, including the Blue Book of 320 runs. See how to apply.
- Learn the runsStudy each run on the map, ride it (most students use a scooter), and learn every point within a quarter of a mile of its start and finish.
- Self-assessmentAn optional practice test on the first 80 runs, within six months of starting.
- Written examinationFive questions on runs and 25 on points, with a 60% pass mark. It has to be taken within two years of receiving your pack.
- Appearances (stages 3 to 5)One-to-one oral exams with an examiner, usually four questions each, graded A to D. They're about 56 days apart at stage 3, then 28, then 21 as you progress.
- Suburban runsLearn an extra 25 routes out to the suburbs.
- Your badgeApply for your licence, attend the pre-licensing talk, and collect your green badge.
How long does it take?
TfL says most students take three to four years. Recent changes have shortened it, with the average falling to around three years in 2025. It depends almost entirely on how many hours you put in. Research on trainees found that those who qualified studied roughly twice as many hours a week as those who didn't, so steady daily study beats occasional cramming.
What does it cost?
TfL's own fees, from the DBS check and medical through to your licence, come to roughly £1,250. The full breakdown is on the apply page.
On top of that, most students spend several thousand pounds over the course of their studies on a scooter, fuel and insurance, maps and study materials, and sometimes a Knowledge school. There's no public funding, although some cab firms sponsor students.
About KnowLDN
KnowLDN is a study app built around how the Knowledge is actually examined: out loud, from memory, on the shortest legal route. Rather than only showing you the runs, it lets you practise them.
- A real road network. Routes are worked out from OpenStreetMap, including one-way streets and banned turns, so the app knows when a route is illegal and can tell you why.
- Practice that checks you. Type your call-over and get it graded against the best legal route, with every mistake pointed out on the map.
- London in 3D. See a run before you ride it, and learn to recognise junctions and street signs from any direction.
KnowLDN is independent and isn't affiliated with or endorsed by Transport for London. For official rules, always check TfL's Knowledge pages.
Ready to start?
Try the West End warm-up with no account, then sign up free for the Blue Book.