This bill, known as the "Unlocking Affordable Housing Act," directs the Secretary of Transportation to establish specific creditworthiness standards for residential and mixed-use development projects seeking financial assistance through the Transportation Infrastructure Finance and Innovation Act (TIFIA) and Railroad Rehabilitation and Improvement Financing (RRIF) programs. These amendments to titles 23 and 49 of the United States Code are intended to facilitate the financing of projects that incorporate housing components. For both TIFIA and RRIF funds, the Secretary of Transportation, in consultation with the Secretary of Housing and Urban Development, must determine appropriate creditworthiness standards for these developments. These standards are designed to both safeguard the financial stability of the respective programs and align, to the extent practicable, with similar requirements established by HUD for its own housing assistance programs, ensuring a consistent and appropriate framework for evaluating such projects. The Act mandates the Secretary of Transportation, in consultation with HUD, to prescribe regulations to implement these new standards within 180 days of enactment. These changes will take effect 180 days after enactment and will apply to all eligible loans or lines of credit issued under the TIFIA and RRIF programs thereafter.