CAR ACCIDENTS



Car accidents

Car Accidents

1. Introduction

Several variables may affect the risk of a driver fatality in the event of a crash. These include driver characteristics such as age, gender and behavior (e.g. alcohol and seatbelt use), crash characteristics (e.g. direction of impact, vehicle speed at impact), and vehicle characteristics (e.g. weight, length, model year, air bags). However, it has been difficult for researchers to assess the independent contribution of these variables. Such analyses require data on a substantial number of variables, and a large sample size to control for numerous potential confounders and to provide accurate risk estimates.

Few databases contain sufficient information to perform meaningful analyses and are readily available to most researchers. One such database is the Fatal Accident Reporting System (FARS) database collected by the US Department of Transportation. For every traffic fatality in the US, information about crash situations, drivers and passengers, and about the vehicles involved is added to the database. The FARS database contains data from 1975 onward. Many variables contained in FARS are not available in other national databases (Fife, 1989), making this database the most comprehensive tool to study fatal crashes. Although there are some biases in the reporting of the information, the quantity of information coded in the database, and number of crashes recorded allows for the control of many potential confounders, and for the calculation of crash estimates more easily generalizable to the general population ( Barr et al., 1993). Further investigation of the relationship between these variables and fatal injuries may suggest strategies to minimize the number of fatal crashes.

2. Methods

2.1. Data

The FARS database contains comprehensive data about crash situations, drivers and passengers, and vehicles, involved in US traffic fatalities from 1975 onward (analyses used 1975-1998 data). It has built-in quality control mechanisms, and allows for the control of many confounders.

The analyses presented were based on driver fatalities only to factor out the effect of seating position. Seating position affects the risk of a fatal injury, with rear center seats as the safest location in a vehicle (Evans and Evans). Also, in multiple vehicle crashes, the risk of fatality is dependent on the characteristics of the other vehicle(s) ( Evans; Evans; Evans and Evans). Therefore, to maximize the interpretability of findings, a model focusing on driver fatalities involving single-vehicle crashes with fixed objects was chosen. Focusing on drivers removed the confounding impact of seating position, and focusing on single-vehicle crashes removed the effect of other vehicle characteristics.

Because crashes are included in FARS only if a fatality ensued, all drivers of single-vehicle crashes in which they were the sole occupants were killed, effectively removing any variability, and possibly biasing the results of the analyses. Including single-occupant crashes in the analyses would have led to a sample of 85% fatalities. To alleviate this difficulty, analyses were performed on crashes where at least two vehicle occupants were present. In all cases, the crash was sufficiently serious to kill at least one occupant, but not necessarily the ...