Cross Section Rating Fields | |||
Rating Inputs | Rating Outputs | ||
Number of miles/sites. Depending on the treatment being evaluated, this may include sites with and without the treatment. In other cases, the range of each independent variable of interest should be adequate (for analysis based on "segments", number of miles should be used; for analysis based on intersections or similar units, sites should be used. | 100+ | Rating for number of miles/sites. | 20 |
Exact number of miles/sites if known. | |||
Number of crashes for all sites combined. | <250 | Rating for number of crashes for all sites combined. | 0 |
Actual number of crashes for all sites combined if known. | |||
At least two years with actual/estimated traffic volume counts in the study period. | yes | Rating for traffic volume counts in study period. | 10 |
Selection bias (similarity of sites with and without the treatment). | some | Rating for selection bias. | 10 |
Appropriate model form (including error terms). | yes | Rating for appropriate model form. | 10 |
Appropriate functional form (including possibility of non-traditional non-GLM forms) | yes | Rating for appropriate functional form. | 10 |
Appropriate consideration of omitted variable bias (i.e., variables known to influence safety were considered as terms in the model or controlled through study design). | no/unknown | Rating for appropriate consideration of omitted variable bias. | 0 |
Appropriate consideration of correlation between independent variables (with significant correlation, the coefficient of variables may have the wrong sign). | no/unknown | Rating for appropriate consideration of correlation between independent variabes. | 0 |
Appropriate consideration of spatial and temporal correlation. | no/unknown | Rating for appropriate consideration of spatial and temporal correlation. | 0 |
CMF is statistically significant at 0.05, 0.10, or 0.15 levels. | 0.15 | Rating for CMF significance level. | 5 |
RATING TOTAL | 65 |
Read more about how the Star Quality Rating scores are determined.