The lack of sufficient traffic caused a default in 1963 on $101 million of revenue bonds sold in 1955 and 1957 to build the Skyway. In 1991, the city redeemed $10.8 million of the bonds through a tender offer. Andrea Bozzo, a senior vice president at Fitch, agreed that historical revenue levels would cover anticipated debt service on the refunded bonds. She said that the Skyway is attracting traffic from parallel roadways that are congested. Chicago Comptroller Walter Knorr said last week that Skyway revenues have increased about 5% over the last five years. Some of the increase can be attributed to toll rate hikes won through bondholder litigation. Last August, a court-ordered increase to $2 per trip from 1.75 went into effect. Knorr said that while the city was using conservative estimates for debt service, higher traffic due to the anticipated construction of floating casinos in northwest Indiana could push revenues beyond those estimates.