A technical proposal has been advanced for a transportation system in which individuals travel through tubes in pressurized capsules on a cushion of air. One individual in a capsule, according to the proposal, will be able to travel up to ten times as fast as an automobile on a highway. Such a futuristic means of conveyance would surely be thrilling for individuals, but the cost of building the new transport tube between two major cities has been estimated at six billion dollars. Even if this doubtful cost figure is accurate, it represents a waste of money. The cost of maintaining the existing roads between the two cities in question is negligible compared to the cost of building the tube, and those six billion dollars can be dedicated to more vital public works projects.
Which of the following, if true, most severely weakens the argument presented above?