The Austin American-Statesman reported Wednesday the expansion would be possible in part from money generated by the Texas 130 toll road. A new stretch opened in October with the nation's fastest speed limit at 85 mph.
Texas Department of Transportation officials estimate the 2-mile project will cost about $140 million.
Environmental reviews must be done. Construction could start in 2014 and take two years to complete.
TxDOT executive director Phil Wilson says the expansion would have free frontage roads.
Construction of toll lanes on Texas 71 between U.S. 183 and Texas 130 had been included in Austin-area transportation plans but were dropped due to tight finances.
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