In this instance, investors apparently will be the losers if the toll project fails. Neither state nor local government has indicated an interest in intervening on behalf of the bond holders. Elizabeth Mabry, executive director of the state Department of Transportation, says the private investor option was selected for the Greenville project because it posed no risk to the state. South Carolina owns the road and is expected to operate it after the bonds are paid off, or if there is a default.

The road was built as a conduit for industrial development in southern Greenville County. But development didn't occur at the anticipated rate, and traffic was not sufficiently high to provide the needed level of toll revenue. The toll road was expected to generate $8.6 million last year, but brought in less than $3 million, according to The Associated Press. The Southern Connector's financial woes will probably preclude the interest of private investors in any similar ventures in this state.

One other toll road operates successfully in South Carolina, on Hilton Head Island. In that instance, tolls repay state highway bonds.

Tolls have been mentioned as a possibility to provide for the construction of other roads, including the last leg of the Mark Clark Expressway and an expressway to Kiawah and Seabrook across Johns Island. While the successful experiment at Hilton Head offers encouragement, the apparent failure of the Southern Connector should give highway officials pause on future toll projects, which presumably would be the responsibility of the state.

The gas tax remains the most dependable user fee for road projects and may well have to be increased to meet the state's overdue road needs.