A student ponders while drawing routes on a map of London in a test center in north London. All London black cab drivers are required to pass the Knowledge in order to be issued with a Hackney Carriage Licence. On average, between three and four years are needed to acquire this knowledge. A recent scientific study has shown that the area of the brain responsible for spatial memory, the hippocampus was significantly larger in taxi drivers. Aboard London taxis, drivers do not use GPS, they know the city by heart, preferring to rely on their memory rather than on modern technologies.

Locations are numbered on a map of central London in a Knowledge test center.

A student draws a route on a map of London in the test center.

Drivers and mechanics of Premier Padmini taxis gather together at a workshop in Mumbai, India on October 4, 2012. The Premier Padmini was manufactured in India by Premier Automobiles from 1964 to 2000 and is based on the design of Fiat's 1100-series cars from the 1960s. The vehicle quickly became the iconic workhorse in Mumbai's fleet of black and yellow taxis until economic liberalisation in the 1990s allowed different makes and models to be produced in India.

A driver waits for customers in front of an apartment building in Mumbai's suburbs on October 3, 2012.

Customers sit in the cramped back seat of a Premier Padmini taxi during rush hour in Mumbai on October 4, 2012.

A taxi driver looks out of his Premier Padmini while stuck in traffic in a slum in Mumbai on October 3, 2012.

A driver waits for customers on Marine Drive in Mumbai on October 2, 2012.

A de-registered Premier Padmini taxi is pictured covered in dust with love hearts etched on its windows in a scrapyard in Mumbai on October 2, 2012.

A taxi driver sleeps on the boot of his Premier Padmini at a taxi park in Mumbai on October 4, 2012.

A British policeman asks a taxi driver, who had apparently arrived following a request to pick up Julian Assange, to leave after he pulled up outside the Ecuadorean embassy in London, where the Wikileaks founder has sought political asylum, on August 16, 2012.

Supporters of Julian Assange gather outside the Ecuadorean Embassy in London on August 16, 2012. Assange has been living inside the embassy since June 19 after requesting political asylum whilst facing extradition to Sweden to face allegations of sexual assault.

A supporter of Julian Assange is held by police outside the Ecuador embassy in London on August 16, 2012.

A woman walks in front of taxis parked to protest against the government's deregulation plans, in downtown Bologna January 23, 2012. Truckers blocked roads throughout Italy and taxi drivers resumed a strike on Monday as opposition mounted to fuel tax rises and economic reforms aimed at opening up competition in protected sectors including transport and pharmacies.

A line of trucks block a ringroad around Turin Italy, as the Alps are seen in background, Monday, Jan. 23, 2012. Truck drivers in Italy angered by an increase in gas prices introduced as part of the government's austerity measures have blocked highways near Milan in the north and Naples in the south. Also protesting Monday were taxi drivers who went on strike across Italy over plans to issue more taxi licenses. The measure is part of a liberalization package approved last week by the government as it seeks to convince investors it has a strategy to deal with its debts. Truck drivers brought their protest to the mainland after bringing goods transport to a near halt in Sicily last week.

Monica, a German trucker gestures on the Turin highway during a truckers' protest against the government's deregulation plans in Turin January 23, 2012. Truckers blocked roads throughout Italy and taxi drivers resumed a strike on Monday as opposition mounted to fuel tax rises and economic reforms aimed at opening up competition in protected sectors including transport and pharmacies.