Why are the London taxi drivers very efficient?

London taxi drivers are Very efficient．They know the capital like the back of their hands．Why? The reason is that they all have gone through a very tough training period to get a special taxi driving license．During this period，which can take two to four years, the would-be taxi driver has to learn the most direct route to every single road and to every important building in London．To achieve this, most learners go around the city on small motorbikes, practicing how to move to and from different points of the city．Learner taxi drivers are tested several times by government officers． The exams are a terrible experience．The officers ask you "How do you get from Birmingham Palace to the Tower of London? " and you have to take them there in a direct line．When you get to the Tower, they won’t say "well done’．They will quicklymove on to the next question．After five or six questions, they will just say"See you in two months’time．"and then you know the exam is over．
    Learner drivers are not allowed to work and earn money as drivers．Therefore,  many of them keep their previous iobs until they obtain their ficenses．The training can cost quite a lot, because the learners have to pay for their own expenses on the tests and the medical exam．