From the IRS: The highway use tax applies to highway motor vehicles with a taxable gross weight of 55,000 pounds or more. This generally includes large trucks, truck tractors and buses. The tax is based on the weight of the vehicle and a variety of special rules apply. These special rules are explained in the instructions to Form 2290.

So yes, trucks do pay more in taxes, but that doesn't help the "roads are free" or the "you didn't pay for that" mantra.