The National Association of City Transportation Officials (NACTO) has published influential guidance on biking and walking infrastructure since the mid-2000s. NACTO has campaigned for states to endorse its guidance so that cities in those states can clearly use its guidance. FHWA and Congress have also promoted the flexibility of jurisdictions to use NACTO guidance.
Whether a state has design guidance on separated and/or protected bike lanes is based on any positive answer indicating that design guidance as part of the League of American Bicyclists' Bicycle Friendly State survey from 2017-2022.