A federal government transportation commission has endorsed a plan to switch from a traditional fuel tax to a pay-per-mile road tax using GPS systems. Rather than an 18-cent per gallon surcharge on gasoline, drivers would be taxed per-mile, with the option of charging more during rush hour. Although the White House has rejected the plan, the National Surface Transportation Infrastructure Financing Commission believes such a system will be put into effect by 2020. Would a per-mile driving tax discourage drivers from getting behind the wheel of fuel-efficient vehicles? Is this plan a better way to distribute the cost of highway maintenance? Larry Mantle takes your calls.