By old Paris, I assume you mean the area inside the Peripherique? Apart from Montparnasse Tower the building heights inside the Peripherique are limited to sev

By old Paris, I assume you mean the area inside the Peripherique? Apart from Montparnasse Tower the building heights inside the Peripherique are limited to seven floors. This has the same effect as San Fran on restricting the density of the inner city, which means most people can't afford to live there and put up with....long commutes. I spent three months working in Paris and many of the younger people lived further out and had a 45min - 1hr commute by public transport or driving. The link you posted talks about narrow streets, this is true in some areas of the city, but Paris also has many wide boulevards. The traffic during peak hour was pretty bad - the French driving on the footpath meme has some truth to it. Also old Paris can be like it is because the CBD is located just outside the Peripherique at La Defense.