I'm not sure what your getting at. Shipping by train is already cheaper. Shipping single packages is already more expensive. Most of the time if you drive to the store the "Shipping" cost is already built in ie. they shipped it from their warehouses to their store. You will also notice that many times goods online are cheaper than in a store. While the price difference is affected by factors, one is the shipping cost is already built in. When you pay for something online it's the cost of the good + a extra shipping cost. Something in the store has already been shipped and that cost is already built in.

My main point is that a use tax on roads does not, and most likely will not, cover all the myriad of benefits that a highway system provides to everyone in the US. Because a road is something everyone benefits from, I feel that some use of general tax revenue can and should go towards working on roads.

I like to think of it this way. The roads are going to cost X dollars. We have to pay that to get roads built and maintained. If we are able to get super granular and we can tally up every use cost to every company and person than we can come up with a exact tax that covers that. The problem is that is nearly impossible to do. Instead we have a use tax that covers some amount and the rest comes out of the general fund. If the use tax is low then shipping is cheap. You pay less for shipping but more in taxes. If usage tax is high you pay more for shipping but need less general fund tax. Here is where you argue who is getting screwed more - the usage tax or the general tax - and that I cant answer. I feel (I know feeling is not scientific) that it all comes out in the wash and everyone is generally happy with the roads. I could be wrong though.