Table 1.
Collision frequencies and rates by recoverability and driver and vehicle characteristics.
| Collisions | Collisions per million miles | |||||||
|---|---|---|---|---|---|---|---|---|
| Drivers1 | Total # collisions | # Non-recoverable | # Recoverable | Total collisions 2 | p-value 3 | Non-recoverable collisions | Recoverable collisions | |
| Total | 6,680 | 2,660 | 1,515 | 1,145 | 5.04 | 2.87 | 2.17 | |
| Gender 4 | ||||||||
| Male | 3,850 | 1,315 | 745 | 570 | 4.16 | ---- | 2.36 | 1.80 |
| Female | 2,830 | 1,345 | 770 | 575 | 6.37* | <.001* | 3.65 | 2.72 |
| Age (years) 4 | ||||||||
| <25 | 162 | 34 | 19 | 15 | 9.58 | ---- | 5.35 | 4.23 |
| 25–54.9 | 6,268 | 2,421 | 1,386 | 1,035 | 4.96* | 0.025* | 2.84 | 2.12 |
| ≥55 | 250 | 205 | 110 | 95 | 5.73 | 0.207 | 3.08 | 2.66 |
| Tenure (years) 4,5 | ||||||||
| <2 | 2,824 | 527 | 305 | 222 | 6.22 | ---- | 3.60 | 2.62 |
| ≥2 | 3,856 | 2,133 | 1,210 | 923 | 4.82* | <.001* | 2.73 | 2.08 |
| Vehicle body type 2, 6 | ||||||||
| Passenger car | ---- | 1,981 | 1,112 | 869 | 5.27 | ---- | 2.96 | 2.31 |
| Other (mostly “crossover” and minivans) | ---- | 679 | 403 | 276 | 4.48* | <.001* | 2.66 | 1.82 |
For counts, drivers were assigned to demographic categories based on the earliest month they appeared in the dataset. No drivers had missing values for any of the variables used in the analysis.
Values with asterisk and bold font denote significant differences between rate compared to rate for reference group, for bivariate relationship with CPMM only.
P-values were generated from a multivariate Poisson regression analysis with gender, age, and tenure together in the model. Significant differences between rate compared to rate for reference group are shown with asterisk and bold font. P-values from univariate tests are in the body of the paper. There was no evidence found for a significant within-driver correlation as the exchangeable working correlation matrix value was <.01.
The first category presented under each group heading (Gender, Age, Tenure, Vehicle) is the baseline category to which all other categories in that group were compared in significance tests using Poisson regression analysis.
The rate for tenure <1 year was 6.73 CPMM and tenure 1-<2 years was 5.77.
Vehicle body type was tested in a univariate Poisson regression analysis, separate from the multivariate analysis of demographic variables.