A public-private-partnership (PPP) is a contractual arrangement formed between public and private sector partners, which allows for more private sector participation than traditionally possible. Emphasis is placed on expanding the private sector's role in designing, constructing, operating, maintaining, and especially financing infrastructure projects. Design-build-finance (DBF) is one prominent type of PPP. The goal of this research is to quantify the various funding sources of DBF PPP projects in the U.S. transportation sector. The methodology consists of a review of the existing PPP literature on DBF practices in the U.S. and abroad, followed by data collection through a combination of public and private sources, published data, and a series of structured interviews with project stakeholders. The paper presents preliminary results stemming from 21 ongoing and fully completed DBF transportation projects, showing private contributions (of debt and equity) account for more than a quarter of the DBF funding for this subset of projects. Overall, this study contributes to the body of knowledge by evaluating the various funding sources of DBF projects and quantifying the potential of private financing sources to accelerate the amount of infrastructure delivered to the public.