Mixed-use development, pedestrian-friendly design, and the incorporation of front porches and alleys are design elements of which of the following?

The design elements mentioned in your question—mixed-use development, pedestrian-friendly design, front porches, and alleys—are indicative of New Urbanism. This urban design movement promotes walkable neighborhoods, a diverse range of housing and jobs, and community-oriented public spaces. New Urbanism emphasizes the importance of creating environments that foster social interactions and connectivity among residents. It argues for a blend of residential, commercial, and recreational spaces that support a vibrant community life, which aligns with the principles you outlined. Overall, these design elements seek to enhance sustainability and the quality of life in urban areas.