The statistical analysis of highway crash-injury severities: A review and assessment of methodological alternatives
Highlights
► This paper provides a state-of-the-practice review of statistical methods for analyzing crash-injury severity data. ► Methodological issues germane to the analysis of injury severity data are discussed. ► Appropriate techniques for addressing these methodological issues are described. ► These techniques range from simple, binary outcome models to more sophisticated models allowing for heterogeneous effects and correlated error terms. ► Areas of opportunity for future research are highlighted based upon advances in computing and richer data sources.
Introduction
Due to the incredible economic and emotional burden traffic crashes impose on society, vehicle manufacturers and transportation agencies are under constant pressure to implement improvements in vehicle and roadway design to reduce the frequency of traffic crashes and the degree of injury sustained by those involved in crashes. It is important to note that reducing crash frequency and reducing crash-injury severity may necessitate different strategic approaches. For example, limiting rates of curvature or superelevation are policies aimed at reducing the potential for crashes while crashworthy median barriers and roadway signs are designed to reduce the level of injury sustained in the event such objects are struck during a crash. In addition to roadway features, advances in vehicle design also have the potential to reduce crash frequency (electronic stability control and anti-lock brakes) or severity (safety belts or airbags) while driver-training programs and targeted enforcement may have potential in reducing both frequency and severity.
The development of effective countermeasures requires a thorough understanding of the factors that affect the likelihood of a crash occurring or, given that a crash has occurred, the characteristics that may mitigate or exacerbate the degree of injury sustained by crash-involved road users. To gain such an understanding, safety researchers have applied a wide variety of methodological techniques over the years. While these various methodological applications have undoubtedly provided new insights, the fundamental characteristics of crash data often result in methodological limitations that are not fully understood or accounted for.
Lord and Mannering (2010) recently provided an assessment of the characteristics of crash-frequency data and the methodological alternatives and limitations for examining such data. The intent of this paper is to provide a similar assessment of data characteristics and methodological alternatives and limitations for examining crash-severity data, highlighting the strengths and weaknesses of each approach and identifying areas of opportunity for future research.1
Section snippets
Characteristics of crash-injury severity data and methodological issues
Injury-severity data are generally represented by discrete categories such as fatal injury or killed, incapacitating injury, non-incapacitating, possible injury, and property damage only.2
Methodological approaches
A variety of methodological techniques have been applied to analyze crash-severity data. The statistical methods employed by researchers have primarily relied on the nature of the dependent variable and various methodological issues associated with the data, as discussed previously. The dependent variables of existing crash severity models are typically either a binary response outcome (e.g., injury or non-injury) or a multiple response outcome (e.g., fatality, disabling injury, evident injury,
Directions for future research
The preceding discussion shows that a wide variety of methodological approaches have been used to study crash-injury severities and that there has been a steady methodological evolution that has sought to overcome known deficiencies in analysis and provide new insights. For example, issues relating to the trade-offs between ordered and unordered models have begun to be addressed and recent applications of random parameter and multi-state models have opened up new ways to account for unobserved
References (130)
- et al.
Modeling rear-end collisions including the role of driver's visibility and light truck vehicles using a nested logit structure
Accident Analysis and Prevention
(2004) - et al.
Exploring the overall and specific crash severity levels at signalized intersections
Accident Analysis and Prevention
(2005) Analysis of driver injury severity levels at multiple locations using ordered probit models
Journal of Safety Research
(2003)Using logistic regression to estimate the influence of accident factors on accident severity
Accident Analysis and Prevention
(2002)- et al.
An empirical assessment of fixed and random parameter logit models using crash- and non-crash-specific injury data
Accident Analysis and Prevention
(2011) - et al.
Effect of vehicle and crash factors on older occupants
Journal of Safety Research
(2003) - et al.
The independent contribution of driver, crash, and vehicle characteristics to driver fatalities
Accident Analysis and Prevention
(2002) - et al.
A copula-based approach to accommodate residential self-selection effects in travel behavior modeling
Transportation Research Part B
(2009) - et al.
The effect of ice warning signs on ice-accident frequencies and severities
Accident Analysis and Prevention
(2001) - et al.
Analysis of injury severity and vehicle occupancy in truck- and non-truck-involved accidents
Accident Analysis and Prevention
(1999)
Analysis of traffic injury severity: an application of non-parametric classification tree techniques
Accident Analysis and Prevention
Willingness to use safety belt and levels of injury in car accidents
Accident Analysis and Prevention
Identifying significant predictors of injury severity in traffic accidents using a series of artificial neural networks
Accident Analysis and Prevention
Factors influential in making an injury severity difference to older drivers involved in fixed object—passenger car crashes
Accident Analysis and Prevention
Collision prediction models using multivariate Poisson-lognormal regression
Accident Analysis and Prevention
A joint econometric analysis of seat belt use and crash-related injury severity
Accident Analysis and Prevention
A mixed generalized ordered response model for examining pedestrian and bicyclist injury severity level in traffic crashes
Accident Analysis and Prevention
Two-vehicle side impact crashes: the relationship of vehicle and crash characteristics to injury severity
Accident Analysis and Prevention
Segment characteristics and severity of head-on crashes on two-lane rural highways in Maine
Accident Analysis and Prevention
Injury severity analysis of accidents involving young male drivers in Great Britain
Journal of Safety Research
The frequency–severity indeterminacy
Accident Analysis and Prevention
Misclassification of the dependent variable in a discrete-response setting
Journal of Econometrics
The crash severity impacts of fixed roadside objects
Journal of Safety Research
Median barrier crash severity: some new insights
Accident Analysis and Prevention
Driver aging and its effect on male and female single-vehicle accident injuries: some additional evidence
Journal of Safety Research
Rainfall effect on single-vehicle crash severities using polychotomous response models
Accident Analysis and Prevention
Differences in rural and urban driver-injury severities in accidents involving large-trucks: an exploratory analysis
Accident Analysis and Prevention
Bicyclist injury severities in bicycle–motor vehicle accidents
Accident Analysis and Prevention
Age and pedestrian injury severity in motor-vehicle crashes: a heteroskedastic logit analysis
Accident Analysis and Prevention
A note on modeling pedestrian injury severity in motor vehicle crashes with the mixed logit model
Accident Analysis and Prevention
Driver injury severity: an application of ordered probit models
Accident Analysis and Prevention
Identification and validation of a logistic regression model for predicting serious injuries associated with motor vehicle crashes
Accident Analysis and Prevention
Overall injury risk to different drivers: combining exposure, frequency, and severity models
Accident Analysis and Prevention
Comprehensive analysis of vehicle-pedestrian crashes at intersections in Florida
Accident Analysis and Prevention
Presence of passengers: does it increase or reduce driver's crash potential?
Accident Analysis and Prevention
Impact of roadside features on the frequency and severity of run-off-roadway accidents: an empirical analysis
Accident Analysis and Prevention
Analysis of large truck crash severity using heteroskedastic ordered probit models
Accident Analysis and Prevention
The statistical analysis of crash-frequency data: a review and assessment of methodological alternatives
Transportation Research Part A
A multivariate Poisson-lognormal regression model for prediction of crash counts by severity, using Bayesian methods
Accident Analysis and Prevention
Markov switching multinomial logit model: an application to accident-injury severities
Accident Analysis and Prevention
Empirical assessment of the impact of highway design exceptions on the frequency and severity of vehicle accidents
Accident Analysis and Prevention
Highway accident severities and the mixed logit model: an exploratory empirical analysis
Accident Analysis and Prevention
Mixed logit analysis of bicyclist injury severity resulting from motor vehicle crashes at intersection and non-intersection locations
Accident Analysis and Prevention
The effects of road-surface conditions, age, and gender on driver-injury severities
Accident Analysis and Prevention
The risk of pedestrian injury and fatality in collisions with motor vehicles, a social ecological study of state routes and city streets in King County, Washington
Accident Analysis and Prevention
Predicting the severity of motor vehicle accident injuries using models of ordered multiple choice
Accident Analysis and Prevention
Exploring motorcyclist injury severity in approach-turn collisions at T-junctions: focusing on the effects of driver's failure to yield and junction control measures
Accident Analysis and Prevention
Motorcyclist injury severity in angle crashes at T-junctions: identifying significant factors and analyzing what made motorists fail to yield to motorcycles
Safety Science
An analysis of motorcyclist injury severity under various traffic control measures at three-legged junctions in the UK
Safety Science
Examining the influence of aggressive driving behavior on driver injury severity in traffic crashes
Accident Analysis and Prevention
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