This paper extends a random preventive maintenance scheme, called repair alert model, when there exist environmental variables which effect on system lifetimes. It can be used for implementing age-dependent maintenance policies on engineering devices. The new model is flexible to including covariates with both fixed and random effects. The problem of estimating parameters is also investigated in details. To do this, it is assumed that the system lifetime distribution belongs to the log-location-scale family of distributions. A real data set is also analysed on the of the results obtained.

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