Here are more of the details from an article at Slate:
“Under Trump’s plan…the federal government would offer tax credits to private investors interested in funding large infrastructure projects, who would put down some of their own money up front, then borrow the rest on the private bond markets. They would eventually earn their profits on the back end from usage fees, such as highway and bridge tolls (if they built a highway or bridge) or higher water rates (if they fixed up some water mains). So instead of paying for their new roads at tax time, Americans would pay for them during their daily commute. And of course, all these private developers would earn a nice return at the end of the day.” (“Donald Trump’s Plan to Privatize America’s Roads and Bridges”, Slate)
Normally, fiscal stimulus is financed by increasing the budget deficits, but Maestro Trump has something else up his sleeve. He wants the big construction companies and private equity firms to stump up the seed money and start the work with the understanding that they’ll be able to impose user fees and tolls on roads and bridges when the work is completed. For every dollar that corporations spend on rebuilding US infrastructure, they’ll get a dollar back via tax credits, which means that they’ll end up controlling valuable, revenue-generating assets for nothing. The whole thing is a flagrant ripoff that stinks to high heaven. The corporations rake in hefty profits on sweetheart deals, while the American people get bupkis. Welcome to Trumpworld. Here’s more background from Trump’s campaign website: