SAFETY STUDY
Adopted: January 18, 1995
FACTORS THAT AFFECT FATIGUE
IN HEAVY TRUCK ACCIDENTS
VOLUME 2: CASE SUMMARIES 
NTSB Number: SS-95/02
NTIS Number: PB95-917002
PDF Document(9 MB)
SYNOPSIS
The Safety Board analysis of Fatal Accident Reporting System (FARS) data indicates that in 1993 there were 3,311 heavy trucks involved in 3,169 fatal accidents, in which 3,783 persons died (432 were occupants of the heavy trucks). Fatigue was coded as a related factor for at least one truckdriver in 1.67 percent (53 or 3,169) of these fatal heavy truck accidents. The Safety Board believes, however, that the incidence of driver fatigue is underrepresented in FARS in general and in FARS specifically with regard to truckdrivers. Research has suggested that truckdriver fatigue may be a contributing factor in as many as 30 to 40 percent of all heavy truck accidents. In 1990, the Safety Board completed a study of 182 heavy truck accidents that were fatal to the truckdriver. These 182 accidents were a census of the heavy truck accidents that were fatal to the driver in the eight participating States. The primary purpose in investigating fatal-to-the-driver heavy truck accidents was to assess the role of alcohol and other drugs in these accidents. The study found, however, that the most frequently cited probable cause was fatigue. The Board believes that the 31-percent incidence of fatigue in fatal-to-the-truckdriver accidents found in the 1990 study represents a valid estimate of the portion of fatal-to-the-driver heavy truck accidents that are fatigue-related.

Because of the significant number of heavy truck-related fatalities and the significant role of fatigue in such accidents, the Board initiated this study of single-vehicle heavy truck accidents to examine the role of specific factors, such as drivers' patterns of duty and sleep, in fatigue-related heavy truck accidents and to determine potential remedial actions. The purpose of the Board's study was to examine the factors that affect driver fatigue and not the statistical incidence of fatigue. Therefore, the Board specifically selected truck accidents that were likely to include fatigue-related accidents; that is, single-vehicle accidents that tend to occur at night. The Board desired to obtain approximately an equal number of fatigue-related and nonfatigue-related accidents through its notification process.

The Board was specifically interested in obtaining accurate information regarding the truckdrivers' duty and sleep patterns for the 96 hours preceding the accident; therefore, the Board limited the accidents to those in which the driver survived and was available to be interviewed by the Board's investigators to reconstruct the previous 96 hours.

The Safety Board investigated 113 single-vehicle heavy truck accidents in which the driver survived. However, because the 96-hour duty/sleep history that was required for the study was not available for 6 drivers, the 6 accidents in which these drivers were involved (Case Nos. 42, 54, 56, 67, 83, and 104) were not included in the study. The study, therefore, analyzes data from 107 single-vehicle heavy truck accidents.

This volume (volume 2, NTSB/SS-95/02) of the report contains case summaries of the 107 accidents that provided the data analyzed in the Safety Board's study. Volume 1 (NTSB/SS-95/01) of the report contains the Board's analysis of the data, its conclusions, and recommendations issued to improve heavy truck safety.

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