Why doesn’t investment in public transport reduce urban traffic congestion?

There is urban traffic congestion in most parts of the world, including Latin America. Among the measures aimed at solving this problem, many cities have built suburban railways or metros. However, these have had little or no effect, as is shown by studies which indicate that investments in the public transport system are incapable of solving this problem on their cars. This article takes the view that when a new metro line or similar system is opened, many travellers who previously used the buses transfer to it, as do a few who previously used their cars.