One simple answer: ROAD MAINTENANCE AND EDUCATION. IIRC, about 30% is diverted to education, and almost all the rest is used just for repair of existing roads. Add in fed funding and there is money for new roads, but not nearly enough for future needs. And inflation (though mild, adds up over the years) reduces that 20 cents further. Shifting the education part back to roads would help, but still fall well short of the cost of the needed roads (we have 4 of the fastest growing metro areas in the country.)
Further, Perry's PR team notwithstanding, if Texans wanted toll roads, someone would have built them using private money to buy the land. Instead he's condemning a ton of farmland that private roadbuilders would love to buy cheap but can't or won't, and he'll simply GIVE it to the private roadbuilders for years, in exchange for them building a road on it that Texans will pay for!
The Trans Texas Corridor projects are to meet future demand, so they are being planned now but not going to be built next year. Private companies haven't built them yet because demand wasn't there yet, but it will be in the next decade. They also don't have the power of eminent domain, which the state would be providing. The state will own the tollway land, and just lease it out to the toll companies. Without ED the roads become too expensive for a private firm to build, another reason why they don't build them without partnering with the state or a county authority. ED can be abused, but most agree that roads are a legitimate use(one of the few) of it.
Sure, it is a visionary project. The problem is that it is also one predicated on his ability to plan better than the people of the state, and rape landowners through condemnation to achieve a private pass-through. And the people of Texas didn't vote a Republican in to plan for them, to manage their affairs for them, but to keep government small and STOP it from planning for them. And they sure didn't vote for Kelo II.
Rhetorical nonsense.
What Perry's plan is all about is avoiding using the money the way it should be, or cutting programs where it shouldn't be, and shifting more taxes onto the road users who have paid the state already to build and maintain roads it ain't building or maintaining.
No, its about leveraging road funding by bringing in private investors who can build it faster, cheaper, and bond against future toll revenue instead of future taxes. Go look at the budget numbers and you'll find that your assertions are false, the gas tax doesn't and won't bring in enough to pay for anywhere close to all the needed roads. Bottom line, there are 3 options: don't build all the roads (didn't work for DC, Chicago, Seattle, Boston, etc.), raise taxes to pay for all the roads, or bring in private investors to pay for the difference between tax receipts and the cost of needed roads.
Do the math.
You ignore the facts. How were the roads built before? With the same funding sources that somehow just don't seem to work now. The more people buying gas, the more money comes in. Why is it that this funding source isn't working? Because government is spending it where it ain't supposed to be spent, on ROADS. Inflation isn't remotely the reason, nor is 'future demand.' If the money weren't being spent inappropriately, it would be plenty enough.
And if the roads are being built to meet future demand, if that demand is so assured, why are private builders not buying the land themselves to guarantee themselves 100% of the profit? Because they can shunt the bill to the state via the condemnation process and avoid having to pay the actual value of the land if Perry carries water for them. You can call it rhetorical nonsense to say that Texans didn't elect Perry to condemn a swath of the state for the benefit of 'future demand' and private builders, but the reality is that 'visionary' government is liberal government, not conservative government. This 'visionary' government is not reacting to the future market, but planning and managing it. And that's not government's role.