WASHINGTON, D.C. — Road tolls cause more traffic to seek free alternatives on secondary highways which heightens the risk and severity of accidents, according to a new study conducted in the US.

Researchers Peter Swan of Penn State University and Michael Belzer of Wayne State University examined potential risks of tolling highways in the US and presented their findings Monday to the Transportation Research Board in Washington. While the main focus of their study was the effects of tolling the Ohio Turnpike, the researchers said the same risks would apply to other regions as well.

“If private operators – or public operators for that matter – set toll rates to maximize profit where congestion is not a significant problem, they can introduce substantial inefficiencies in the overall road transportation network and actually increase congestion and safety hazards in other parts of the system that they do not own and control,” Swan and Belzer reported. “These inefficiencies, the cost of which are borne by the public and not by the private toll road owner who is focused on profit for his particular part of the network, can only exist when private operators control particular strategically located roads through a purchase or long-term lease.”

The researchers suggested the turnpike could maximize revenue by instating a truck toll of 46 cents per mile. However, they pointed out that would likely be enough to drive trucks to alternative routes. In fact, they said the number of trucks on the free alternatives, which aren’t designed to accommodate high heavy-duty traffic volumes, would quadruple.

“Because we know that secondary roads pose greater safety hazards, the safety cost of diversion will be substantial,” the study reported. “We know enough about the frequency and severity of crashes based on highway type to suggest that a substantial increase in crashes, crash severity, and fatalities in the state of Ohio probably would occur as a result of this diversion.”

The study can be read in its entirety at: www.thenewspaper.com/rlc/docs/2008/tolldiversion.pdf.