Colombian capital Bogota is organising its second annual 'day without cars' tomorrow, when the city will again reflect on the meaning of the car, the best way of using it and its real use in society. Nearly a million vehicles use the city each day, but tomorrow only buses and taxis, ambulances, diplomats' cars and approved commercial vehicles will be allowed out. Bogotá has no subway but commuters use a new articulated bus system called Transmilenio, though it is not large enough to transport everyone.