BEST CASE scenario, it would work like this:
At first, 30% or so of drivers who have an alternate route will take it, or take public transport, relieving some traffic on the highway in question.
The other 70% have no other viable choice and are asked to bend over and pay.
After a few months of “traffic is so much better now,” the other 30% will decide it’s worth it to pay the toll, and start doing so, making the road congested again.
Voila. Traffic still bad, and government coffers now full of toll cash.
Brilliant analysis - I can see your entire scenario unfolding in that way.