"Regressive tax" is not a term that I can take credit for creating, thanks. It's true that food takes up a higher percentage of a person's income as the person's income decreases, but I'm not sure what that has to do with our discussion. Everyone has to eat. It's the facts of life that food takes up a higher percentage of a poorer person's income.
Another problem with toll roads, besides the ones I've mentioned, is that they create tiers of highways--those for the rich and those for the poor. It's similar to the idea of creating an Internet for rich people--an idea that some groups are advocating and others are fighting. Egalitarian is better. Let everyone use the roads.
You said that tolls are regressive. They are not, except in the overly-broad sense you yourself created. A toll is essentially a user-fee, and about as close to being the opposite of "regressive" as something can get.