Imagine how bad it would be without the tube and busses! All these people trying to drive in London? Just thinking about it I shudder and I've never even seen London.
According to a study conducted in 1000 cities in 50 countries based on data from connected vehicles and phones. Not disagreeing with the premise but I expect there are plenty of other more "congested" cities, visit Manila or Jakarta for example. The UK should however definitely do more to fund its public infrastructure.