(FORTUNE Magazine) -- Someone call Lou Dobbs: America's highways are are up for sale. States are auctioning off the rights to manage their roads - often to overseas firms. What's driving the trend?

1. Why are states doing this? They're strapped for cash. The federal Highway Trust Fund is projected to be $2.3 billion in the hole by the end of 2009. Indiana's major toll road lost money five of the past seven years. Instead of raising taxes or borrowing money for repairs, Governor Mitch Daniels raised $3.8 billion from a partnership of Australia's Macquarie and Spain's Cintra for a 75-year lease.

2. Why are foreign companies doing the bidding? Privately owned toll roads have been popular in Europe and Australia for years. Macquarie and Cintra have also leased the Chicago Skyway, and Macquarie is behind California's new South Bay Expressway. They expect a 12% to 14% return on each deal.

3. Are more privately controlled toll roads on the way? Yes. Some $40 billion worth of agreements are in the works. Texas, for example, anticipates $7.2 billion in private funds for a new highway from Oklahoma to Mexico. And Wall Street is jumping in. Banks like Goldman Sachs, which made $9 million brokering the Skyway lease, and J.P. Morgan have created infrastructure units to put together deals.

4. Will my tolls go up? Bet on it. Private operators will probably hike prices. But there will be caps in most cases - initially at a set amount and then pegged to inflation, the GDP, or a fixed percentage of current rates.