An important part of testing is establishing assessment criteria and collecting data.

I wish more laws would pre-state what their intended outcome and success would look like.

you haven't described the observations or the sample

That's not an A/B test because it has no way of controlling for broader economic trends over time. How do you figure out if what you're seeing is because of that one thing that changed, or the enormous list of other things that also changed around the same time?

A more valid design would be randomly assigning some cities to institute congestion pricing, and other cities to not have it. Obviously not feasible in practice, but that's at least the kind of thing to strive toward when designing these kinds of studies.