SAN ANTONIO -- A billion-dollar Texas toll road with an 85 mph speed limit -- the fastest in the nation-- has drawn about half the number of drivers expected in its initial months of operation, a performance low enough that the private company that built it is facing a downgraded credit rating, according to Moody's Investor Service.The Texas 130 toll road extension generated almost $2.6 million in toll revenue in the first six weeks that the road was opened in late October, according to state records obtained by the San Antonio Express-News. At least 202,861 vehicles traveled on some part of the road during that time period. The extension is in a largely rural area between Interstate 10 in Seguin and a road south of Austin.Moody's announced March 15 that it is investigating a possible downgrade of the credit rating of the SH 130 Concession Co., which spent $1.4 billion to build the toll road extension and will operate and maintain it for the duration of a 50-year lease with the state.The report also indicates that the company could struggle to make future debt payments if traffic revenues do not increase. Part of that debt is a $430 million federal loan.The SH 130 Concession Co. is made up of Spanish-based Cintra and San Antonio-based Zachry American Infrastructure. Although the operating history of the toll road is limited, the shortfall was so significant that Moody's said it warrants a review.It was unclear what the revenue and traffic volume expectations were for the toll road extension during the period for which records were requested by the Express-News. It also was unclear whether a downgraded credit rating could increase the cost of borrowing for the firm.