Exploring thresholds for a double acceleration movement in sustainability transitions

This paper examines how acceleration in sustainability transitions can be conceptualized and measured. Much of the existing literature conceptualizes acceleration as a specific phase of the transition process, typically measured as the rapid scaling of technological products. We argue, however, that acceleration should go beyond a sequential phase model and should not be conflated with technological diffusion; rather, it should be conceptualized as a modular process and measured through rule (or institutional) changes. To reflect this perspective, we introduce the concept of acceleration thresholds and develop a framework—the double acceleration movement framework—that captures transitions as a set of parallel and modular processes occurring across multiple thresholds. To test our framework, we develop a methodology to measure these thresholds and apply it in the case of China's energy and mobility transitions acceleration. Our analysis demonstrates how the framework can trace acceleration patterns, offering a new lens for studying system change beyond technology diffusion. We conclude by highlighting the significance of accelerating thresholds for sustainability transition research and their potential to connect with emerging work on social tipping points. Additionally, we suggest directions for future research, including refining our conceptualization by incorporating spatial perspectives, focusing more on directionality, and developing new AI tools for monitoring acceleration in global low-carbon transitions.