The 24-page plan, outlined in a "Forward Momentum" report that escaped widespread attention when published in February, drew prompt objections Thursday from state lawmakers and activists fighting the spread of privately run toll roads.

"I think it's a dreadful recommendation on the part of the transportation commissioners here in Texas," said Senate Transportation and Homeland Security Committee Chairman John Carona, R-Dallas.

"I feel confident that legislators in Austin would overwhelmingly be opposed to such an idea," he said. "The simple fact is that taxpayers have already paid for those roadways. To ask taxpayers to pay for them twice is untenable."

The report not only advocates turning stretches of interstate highways into toll roads, but it also suggests tax breaks for private company "investment" in such enterprises.

Along with that, it calls for altering the tax code to exempt toll road owners from paying income taxes.

The agency's (TxDOT) attempt to influence Congress comes in on the heels of its multimillion-dollar advertising campaign touting the lightning-rod Trans-Texas Corridor plan and other toll roads.

With an estimated price tag of $7 million to $9 million, the "Keep Texas Moving" campaign comes even as transportation officials warn of an $86 billion shortfall for needed highway construction.

"It's less than 50 cents a Texan," Transportation Department spokesman Chris Lippincott said in defense of the ad campaign. "We could sit down and buy them a cup of coffee for that kind of money."

Lippincott said he's surprised by the reactions, noting the agency discussed the issue at four public meetings and sent a link to the draft report last December to all members of the Texas Legislature.

Besides, he said, state law would prevent the conversion of interstate highways into toll roads unless such a plan gained votes of county commissioners and taxpayers in a referendum.

Anti-toll road activist Sal Castello, the Austin-based founder of the TexasTollParty.com, said he's frustrated by the "schemers and the scammers" who "never stop" divisive toll road proposals despite widespread opposition and fretted that a required referendum could be creatively worded to disguise the nature of toll road conversions.

Carona said he objects to the agency's attempts to persuade Congress to allow federal highways to turn into toll roads because the interstate system was built as part of the national defense.

Rep. Lois Kolkhorst, R-Brenham, said the report appears to recycle ideas that led the Legislature this spring to pass a moratorium on construction of the Trans-Texas Corridor, a mammoth toll plan that's the cornerstone of Gov. Rick Perry's highways building proposal.

"This is not only double taxation, it is a violation of the trust that should exist between citizens and government," she said. "Existing Texas highway lanes built with our tax dollars should not be converted to toll roads and taxed again."

Perry spokesman Robert Black said the report in no way contradicts Perry's repeated promise on highways that "if it's free today it will be free tomorrow."

That still holds true, he said, unless local voters say otherwise.

Meanwhile, "Texas will work to educate Congress of the importance of including reasonable and efficient funding solutions, such as tolling, in the next (highway funding) reauthorization bill," the department's report promises.

Next week Democratic state Reps. Joe Farias and David Leibowitz of San Antonio will join Rep. Nathan Macias, R-Bulverde, at a condemned gas station in San Antonio to air objections to the transportation department's tolling ideas and ad campaign.

"TxDOT has crossed the line on a number of fronts in recent weeks, and elected representatives are prepared to fight," said Terri Hall, founder of Texans United for Reform and Freedom, a grass-roots group to promote nontoll solutions to Texas' transportation needs.

polly.hughes@chron.com