Which cities in Europe have the worst traffic?

Which cities in Europe have the worst traffic?
How good are train services around Europe? Well, it has some of the best and worst train services in world.
Four of the world’s top 5 railway networks are in Asia.
Which European systems have a metro/ subway system and when was the first line opened?
Trolleybuses are often associated with the Soviet Union, communism and Cold War era Eastern Europe. But how much of that is still true today?
Japan is renowned for its punctual and convenient public transport system. But how much of the country does it actually cover?