Temporal instability and age differences of determinants affecting injury severities in nighttime crashes

•This paper investigated the differences of determinants affecting nighttime crashes among young drivers, middle-age drivers and old drivers.•This paper revealed temporal instability and non-transferability of contributors determining nighttime crashes among young drivers, middle-age drivers and old drivers.•This paper utilized three groups of random parameters multinomial logit models with the heterogeneity in the means and variances.•This paper conducted a comparison between out-of-sample and within-sample prediction.