What Tackles Vehicle GHG Emissions in California: Regional Plan Adoption or Local Leadership?

The California Senate Bill No. 375 (SB 375) serves as a model policy for reducing greenhouse gas (GHG) emissions by integrating transportation and land-use planning through regional and local policies. The 18 California Metropolitan Planning Organizations (MPOs) are tasked with developing Sustainable Communities Strategies (SCS) to guide emissions reductions, often implemented locally through Climate Action Plans (CAPs). However, CAPs are voluntary, and misalignment with SCS objectives can undermine their effectiveness. This study examined 25 California cities using content analysis and regression modeling to explore whether independent local actions, supported by community engagement, activist strategies, and leadership, are more effective than regional alignment in reducing vehicle trips. The findings show that while aligning regional and local plans is important for equity and resource distribution, local activist leadership in addressing specific issues, such as parking and public education, achieves significant reductions in vehicle trips. These efforts lead to a 20% increase in non-auto commuting, even without a mandated regional alignment. Additionally, regional strategies such as climate-friendly infrastructure and mass transit are crucial for addressing resource disparities between lower-income communities with limited volunteer capacity and wealthier communities that benefit from robust regional plans and strong local leadership. This study provides critical evidence of the effectiveness of regional and local approaches, emphasizing the need for a balanced, multi-scalar framework to enhance transportation emission reductions and climate resilience.