Bicycle enthusiasts and certain tourists who use the Ohio Turnpike are paying up to 75 percent more in tolls thanks to a change in vehicle classification that took effect toward the end of last year. Traditionally, toll roads charged more for vehicles based on their weight and number of axles on the theory that these vehicles impose a substantially greater burden on the road system.

"When carriages which pass over a highway... pay toll in proportion to their weight, they pay for the maintenance of those public works exactly in proportion to the wear and tear which they occasion of them," economist Adam Smith explained in the Wealth of Nations two-hundred and thirty-four years ago.

The turnpike discards this reasoning in order to boost the full-trip cash price of a car with a bicycle roof rack or a minivan with a cargo carrier by 66 percent from $15 to $25. For those using E-ZPass, the increase is 75 percent, from $10.25 to $18. Under an already established toll hike schedule, bicyclists will be forced to pay as much as $28 for the trip beginning in January 2012.

The extra charge applies to any vehicle that measures seven feet, six inches tall. That means a family Nissan Quest minivan with luggage on the roof measuring just one-foot tall would put the vehicle into the "Class Two" territory previously reserved for three-axle commercial vehicles. Likewise, an ordinary car with a bicycle mounted on the roof would also fall into the more expensive category, even though a bicycle weighs only about as much as five gallons of gasoline and imposes no extra wear on the road.

Turnpike Executive Director George Distel suggested in comments to the Cleveland Plain Dealer newspaper, which first reported the story, that this was an unintended consequence of the way in which an automated laser scanning device attempted to identify large, commercial vehicles. This excuse is undermined by the Turnpike's own website which clearly shows cars with bicycles on the roof and a minivan with a luggage carrier among the types of Class Two vehicles (view Turnpike chart).

The reason for this has not changed in 234 years. Public toll roads, then as now, are seen as a substantial revenue source for the state.

"In Great Britain, the abuses which the trustees have committed in the management of those tolls have in many cases been very justly complained of," Smith wrote in 1776. "At many turnpikes, it has been said, the money levied is more than double of what is necessary for executing, in the completest manner, the work which is often executed in very slovenly manner, and sometimes not executed at all."