you're both right.

generally what's happening is a combination of:

    * making pedestrian zones (i.e. banning)
    * deny access to certain types / times  (no vans, no old cars, etc.. i.e. also banning)
    * reducing roads (i.e. 2 > 1 lane, thus reducing attractivity)
    * raising driving prices (the congestion / air quality certificates you mention)
    * reducing access to parking (remove places, make them more expensive, etc)

.. all the while increasing alternatives (i.e. use those reduced lanes for bikes)