Faster, better, cheaper.

As President Trump prepares to deliver a speech on Wednesday about infrastructure, his administration is promoting the benefits of having local governments work with private corporations to build, repair and manage the nation’s ailing roads, bridges and airports.

Public-private partnerships, as they are known, have many potential benefits. Companies can complete projects quicker and more cheaply than governments can, proponents say. Letting private industry take the lead can also limit the amount of debt that cities and states need to take on.

Yet in the United States, public-private partnerships represent a tiny fraction of infrastructure spending. On toll roads, for instance, where they have been used the most, they accounted for just 1 percent of all spending between 1989 and 2011, according to a report by the Congressional Budget Office.

And whatever the advantages of giving the private sector a stake in public works — rather than leaving the government in control — experts agree that while some public-private partnerships may result in near-term savings, there is little hard evidence that they perform better over time.