Association between Truck Crashes due to Mechanical Failure and Truck Age

Table 6

Poisson model for truck crashes occurring due to mechanical failure by truck age (N = 41).

Variable	Coefficient	Standard error
Intercept	−15.8256	1.77368	<0.0001
Log (estimated number of trucks)	1.16042	0.10521	<0.0001
Truck age	0.09902	0.01413	<0.0001
Goodness-of-Fit	Statistic	Equation
Log-likelihood (full)	−111.37728	—
Log-likelihood (null)	−310.88424	—
McFadden’s R^2	0.64059
MAE (median absolute error)	3.41879
RMSE (root mean squared error)	4.93716
MAPE (mean absolute percentage error)	0.20674

is the observed crash count at truck age i, and is the predicted crash count at truck age i. Significant at 99% confidence level.