Hi,
Actually I’m a PhD international student in USA; recently I started my research which concerns in a freight forecasting model. I just want to ask about the tax imposed in the fright in general in USA specially for a road and rail freight and how it is calculated
Thanks in advance

Individual long-haul truckers pay a road tax for the right to haul freight on U.S. roads. It is a substantial tax and goes under the acronym IFTA (for International Fuel Tax Agreement).

The tax is administered by the states. You can find out what you need to know by Googling 'IFTA Tax'.