I'm sorry to say this, but you are completely wrong. The trucking industry is at its limit for cheaper freight. The biggest issue is the fuel costs and the mileage we get with trucks today. The newer trucks usually only get around 4-6 MPG. It's because of all the EPA bs.
Why do you think the price of a gallon of milk increased back when the cost of fuel went up? Taxing the trucking industry even more is the wrong way to go and it will hurt the economy even more.
If you want to tax someone, tax the people that don't carpool.