Operational flexibility is an essential criterion for evaluating air quality monitoring systems, particularly in rapidly evolving urban environments where pollution sources may vary spatially and temporally. Flexibility reflects the ability of a monitoring system to adapt to changing monitoring needs, respond to pollution events, and redeploy measurement equipment to different areas of interest. Several studies have highlighted that mobile sensing platforms significantly improve the adaptability of monitoring networks compared with traditional fixed monitoring stations due to their ability to relocate and cover multiple areas (Apte et al., 2017; Castell et al., 2017). To quantitatively evaluate operational flexibility, a composite flexibility index (FI) is introduced:

The ability to adapt operations stands out as a crucial factor when assessing air quality monitoring systems, especially in dynamic urban settings where pollution sources change across different locations and time periods. This adaptability measures how well a monitoring system can adjust to shifting requirements, handle pollution incidents, and move measurement devices to various target areas. Research has demonstrated that mobile sensing platforms offer considerably better adaptability for monitoring networks than conventional stationary monitoring stations because they can move around and monitor multiple locations (Apte et al., 2017; Castell et al., 2017). A composite flexibility index (FI) has been developed to measure operational flexibility in quantitative terms: