Quite the opposite. After a certain point roads start being congested because, while it takes time in traffic to move, the road is "free" and so people use it. There's been a growing voice in Toronto, Canada saying that tolls should be introduced: we have some of the worst traffic jams (worse than LA), and stretches of Highway 401 get over 500,000 cars an hour (the busiest in the world).
How about the situation where people use free roads to avoid expensive tolls, resulting in more congestion on the free roads, while the toll road remains underused? One might expect the toll to be lowered to balance this out, but it seems the tolls only go higher.