Since the whole point is to reduce congestion, implementing a cap (price ceiling) is absurd. When a price ceiling is set, a shortage occurs. In the case of road usage pricing, a shortage means a shortage of capacity.

In other words, you end up with traffic congestion and tolls, the worst of both worlds.

I read a similar thing about Houston where it's capped at $8 and has little effect on reducing congestion. The first course of action should be to remove the price cap. (And expand the number of paid lanes, which would decrease the cost paid by drivers by spreading it out over more lanes.)

You can't have your cake and expect it to eat it too by imposing usage pricing with price caps.

Economics 101: price ceilings cause shortages.