Design-Build is one of the most limited forms of PPP, as it varies only slightly from the traditional Design-Bid-Build model. Because this model only combines contracts for design and construction that would normally be issued separately, the public likely views it as more of a streamlining of the contracting process rather than a step toward privatization. As such, the political risks of Design-Build agreements are low, and many states readily allow their highway agencies to pursue this PPP model.
With less than half of the states in the country presently allowing highway PPP projects, and even fewer pursuing the riskier concession models, it is uncertain whether most states are willing to attempt the Build-Operate-Transfer or Design-Build-Finance-Operate schemes. Thirty-one of the forty-four major highway PPP projects undertaken in the United States since 1991 have been Design-Build (AECOM Consult 2007). PPP legislation must carefully balance the desire to protect government agencies from risks while still keeping proposals attractive to the private sector when compared to the other investment opportunities available on the private market. Trying to offload too many risks to the private sector or not providing enough government-backed incentives will diminish private interest in a state's PPP proposals.