By providing flexibility, SIBs can help States get projects underway sooner. As loans are repaid, the proceeds are available to fund additional projects.[318] The SIBs may also aid States in another aspect of highway ventures.[319] However, besides the financial rules of the Federal highway program, the law imposes conditions on Federal aid that may increase the cost of a project funded by a SIB loan.[320] For example, a project built with Federal-aid must meet the prevailing-wage requirements of the Davis-Bacon Act.[321] Federal requirements apply to all projects financed by federally approved SIBs under the TEA-21 SIB program.[322] Federal requirements do not apply to projects financed through repayments for 39 federally approved SIBs authorized under the NHS Act. Federal requirements do apply to projects financed through repayments for SIBs authorized under TEA-21. Only two States have SIBs operating under the authority granted in TEA-21. The application of Federal requirements to all projects, even those financed through repayments, may have discouraged the other three States from operating their SIBs under the TEA-21 authority.