traffic is a crappy externality that harms everyone, drivers, non-drivers. non-drivers are harmed by pollution, slower buses and cabs, noise, slower emergency response times. drivers are harmed by all those things as well plus the stress and inconvenience of extreme traffic. the point of congestion pricing is to reduce the so-called "traffic tax" that everyone pays into one that is just a toll, that only drivers pay. reducing traffic is a direct goal of the toll.