Figure 1.

Relationships between the number of work days and median CV $R^2\mathrm{s}$ across complete and alternative mobile monitoring designs according to the number of sites (A), visits (B), seasons (C), and days and hours (D) from the ACT-TRAP mobile monitoring campaign. The “ref” and “ref*” indicate the complete all-data reference and reduced reference designs, respectively. The open red circles and blue diamonds represent cost (number of work days) and CV $R^2\mathrm{s}$, respectively, from the complete reference design that serves as the gold standard for comparing spatially reduced alternative designs with fewer sites (A) or temporally reduced alternatives with fewer visits (B). The red stars and blue diamonds with cross represent work days and CV $R^2\mathrm{s}$, respectively, from the reduced reference design that is equivalent to the complete all-data design except reduced to 12 visits instead of $\sim 29$ and is used as the “complete” design for temporally restricted alternative designs with fewer seasons, days, or hours (C and D). In (B), the black dotted horizontal and vertical lines highlight the CV $R^2$ for the reduced reference design. Note: ACT-TRAP, Adult Changes in Thought Traffic-Related Air Pollution; CV, cross-validated.