Table 5.
Ordinary Least Squares Multivariate Regression Results For In-Cabin Concentrations (Cbus, μg/m3
| Effect Estimate | Standard Error | t-value | p-value | Model-Based R2 | CV R2 | |
|---|---|---|---|---|---|---|
|
Models Without Roadway Concentrations (N=85) | ||||||
| Intercept | 6.45 | 4.34 | 2.21 | 0.14 | ||
| New Buses with DOCs | −15.15 | 2.89 | 27.48 | <0.001 | 0.21 | |
| Ambient Relative Humidity (%) | 0.26 | 0.06 | 18.06 | <0.001 | 0.13 | |
| Frequent Maintenance (<60 days) | 5.42 | 2.33 | 5.43 | 0.02 | 0.07 | |
| Opacity (%) | −0.26 | 0.12 | 4.29 | 0.04 | 0.04 | |
|
Overall Model Fit |
|
|
|
|
0.45 |
0.17 |
|
Models With Roadway Concentrations (N=46) | ||||||
| Intercept | 30.33 | 5.15 | 34.69 | <0.001 | ||
| Roadway Concentrations (μg/m3) | 0.46 | 0.14 | 11.38 | 0.0017 | 0.36 | |
| New Buses with DOCs | −13.331 | 2.77 | 23.18 | <0.001 | 0.13 | |
| Maintenance Cycle (days) | −0.17 | 0.05 | 11.07 | 0.002 | 0.08 | |
| Windows Mostly Open | −5.19 | 2.38 | 4.74 | 0.04 | 0.05 | |
| Overall Model Fit | 0.62 | 0.32 | ||||