A mixed generalized ordered response model for examining pedestrian and bicyclist injury severity level in traffic crashes

Abstract

This paper proposes an econometric structure for injury severity analysis at the level of individual accidents that recognizes the ordinal nature of the categories in which injury severity are recorded, while also allowing flexibility in capturing the effects of explanatory variables on each ordinal category and allowing heterogeneity in the effects of contributing factors due to the moderating influence of unobserved factors. The model developed here, referred to as the mixed generalized ordered-response logit (MGORL) model, generalizes the standard ordered-response models used in the extant literature for injury severity analysis. To our knowledge, this is the first such formulation to be proposed and applied in the econometric literature in general, and in the safety analysis literature in particular.The MGORL model is applied to examine non-motorist injury severity in accidents in the USA, using the 2004 General Estimates System (GES) database. The empirical findings emphasize the inconsistent results obtained from the standard ordered response model. An important policy result from our analysis is that the general pattern and relative magnitude of elasticity effects of injury severity determinants are similar for pedestrians and bicyclists. The analysis also suggests that the most important variables influencing non-motorist injury severity are the age of the individual (the elderly are more injury-prone), the speed limit on the roadway (higher speed limits lead to higher injury severity levels), location of crashes (those at signalized intersections are less severe than those elsewhere), and time-of-day (darker periods lead to higher injury severity).

A latent variable representation of count data models to accommodate spatial and temporal dependence: Application to predicting crash frequency at intersections

“…In the standard ordered probit (SORP) model of Equation (1), the thresholds ψ are assumed to be fixed across individuals, though this need not be the case (see Terza, 1985, Pudney and Shields, 2000, King et al, 2004, Kapteyn et al, 2007, Eluru et al, 2008, and King, 2009; see also Greene and Hensher, 2010, Chapter 7 for a discussion). Following these earlier studies, consider that the thresholds are parameterized as a non-linear function of a set of 1 The exclusion of a constant in the vector x q of Equation (1) is an innocuous normalization as long as all the intermediate thresholds (ψ 0 through ψ K-1 ) are left free for estimation.…”

Road Traffic Congestion and Crash Severity: Econometric Analysis Using Ordered Response Models

“…However, a recent study byYamamoto et al (2008) suggested that traditional 'unordered' models may provide unbiased estimate of the parameters, especially in the case for missing data such as under-reporting. Readers are also referred to a number of existing studies that recommend to explore alternative models (Milton et al, 2008;Eluru et al, 2008, Anastasopoulos et al, 2008.…”

Factors affecting hospital admission and recovery stay duration of in-patient motor victims in Spain

“…The seating position of the victim has likewise been related to the severity of injuries (Smith and Cummings, 2004;Newgard et al, 2005). The crash severity behaviour of non-motorized road users has also been extensively investigated (Chong et al, 2010;Tarko and Azam, 2011;Eluru et al, 2008). Injuries described in the legislative scale are classified according to their nature and the body location in order to reduce the number of injuries on the legal scale into a manageable number of diagnostic categories, inspired by the diagnostic matrix of the International Classification of Diseases (ICD)-9-CM codes developed by Barell et al (2002).…”