Tolling existing roads or lanes, or even new ones, is frequently argued to be double taxation, implying that drivers are unfairly taxed twice (through both tolls and fuel taxes). This argument, however, ignores the fact that motor fuel taxes do not pay for the full cost of providing the road network. Paying two different taxes to support an activity, unless the combined taxes exceed costs, is not implicitly unfair. Currently, people pay a vehicle registration fee as well as the gas tax to drive on roads. Indeed, an array of transportation funding sources, including tolls, are used by governments to pay for transportation systems. Tolls are one tool used to raise transportation revenues-in some cases, as the only way to fund modern roads, given insufficient standard transportation revenues.