“…Our choice of the ordered-response specification for injury severity deserves some explanation here. Many earlier injury severity studies have used such a specification to appropriately recognize the ordinal nature of the injury severity levels (see, for example, Xie et al, 2009, Christoforou et al, 2010, Haleem and Abdel-Aty, 2010, Quddus et al, 2010, Jung et al, 2010, Zhu and Srinivasan, 2011. In recent years, unordered-response specifications have also been considered (see, for example, Rifaat et al, 2011, Yan et al, 2011, Malyshkina and Mannering, 2009, Huang et al, 2008, Milton et al, 2008, Kim et al, 2010, and Moore et al, 2011.…”