Back before I moved to London and had to get rid of my car (sob), I used to do some of my best pondering while stuck in traffic. A thought that kept coming back to me was an optimisation problem about when is the best time to take your driving test. Driving lessons are expensive but a driving test is even more expensive - therefore how many lessons should you have before you take your test so as to spend the least amount of money? I always figured there would be some mathematical optimisation technique to come up with an answer that takes the price of driving lessons, the price of a driving test and a function that estimates your likelihood of passing the driving test given the number of lessons you’d had. However this always seemed to hurt my head too much to work out especially given I was trying to concentrate on driving at the same time. However since starting this blog I decided to explore this idea I’ve had for a few years and try to work it out.