It’s a little bit regressive as you mention, but forcing the users to pay also encourages businesses to find ways to economize and thus minimize the impact of the tax on their customers. It’s also less regressive to pass along a small amount of tax in the cost of items (the portion of the cost of most things we buy made up by transportation costs is very small, and the tax is a small portion of that), than it is to burden car-less poor people with the cost of building roads that they don’t drive on.
That actually sounds sensible so maybe you're right.
Here in Sydney we just opened a tolled tunnel, and to ease congestion up above on the older commuter road all trucks must use this tunnel. I don't know all the factors but it sounds like the best option for the people, they have a choice and trucks pay their way.
