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WHY ARE SAFETY REGULATIONS REQUIRED?

Author / Coordinator:  
SAFETY STUDY
January 1995

FACTORS THAT AFFECT FATIGUE IN HEAVY TRUCK ACCIDENTS

VOLUME 1: ANALYSIS

NTSB Number: SS-95/01

NTIS Number: PB95-917001
 
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). Research has suggested that truck driver 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 truck driver. 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 3 1-percent incidence of fatigue in fatal-to-the-truck driver 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 were not included in the study. The study, therefore, analyzes data from 107 single-vehicle heavy truck accidents.

Based on the determination of probable cause, 58 percent of the accidents (62 of 107) were fatigue-related. The remaining 42 percent of the accidents (45 of 107) were not fatigue-related. Nineteen of the 107 drivers stated that they fell asleep while driving.

The Board emphasizes that the conclusions reached in this study are not based on a set of anecdotal accidents, although the-merits of such Board studies have proven valuable in the past.

Rather, the results are based on a multivariate statistical analysis (a multiple discriminate analysis) that was performed to simultaneously evaluate the relationship of a set of measures of the drivers’ duty and sleep times to the groupings of accidents established by investigators' determination of probable cause (fatigue related and nonfatigue-related accidents). The statistically significant analysis determined that the most important measures in predicting a fatigue-related accident in this sample are the duration of the last sleep period, the total hours of sleep obtained during the 24 hours prior to the accident, and split sleep patterns.

Based on the results of the analysis, the safety issues discussed in this study are:

  • the factors that affect fatigue-related accidents,
  • the adequacy of the Federal Highway Administration's hours-of-service regulations, and
  • the adequacy of truckdrivers' understanding of the factors affecting fatigue.

As a result of this study, recommendations were issued to the Federal Highway Administration, the Professional Truck Driver Institute of America, the American Trucking Associations, Inc., the Commercial Vehicle Safety Alliance, the National Private Truck Council the Independent Truck Owner Operators, the Owner-Operator Independent Driver's Association, the International Brotherhood of Teamsters, and the National Industrial Transportation League. The recommendations focus on the Federal hours-of-service regulations and truckdriver education.

RECOMMENDATIONS

As a result of this safety study, the National Transportation Safety Board made the following safety recommendations:
to the Federal Highway Administration:

Complete rulemaking within 2 years to revise 49 CFR 395.1 to require sufficient rest provisions to enable drivers to obtain at least 8 continuous hours of sleep after driving for 10 hours or being on duty for 15 hours. (Class II, Priority Action) (H-95-1)

Complete rulemaking within 2 years to eliminate 49 CFR 395.1 paragraph (h), which allows drivers with sleeper berth equipment to cumulate the 8 hours of off-duty time in two separate periods. (Class II, Priority Action) (H-95-2)

Examine truckdriver pay compensation to determine if there is any effect on hours-of-service violations, accidents, or fatigue. (Class II, Priority Action) (H-95-3)

Complete rulemaking within 2 years to amend 49 CFR Part 392 and 395 to prohibit employers, shippers, receivers, brokers, or drivers from accepting and scheduling a shipment which would require that the driver exceed the hours-of-service regulations in order to meet the delivery deadline (similar to current regulations regarding schedules which would require the driver to exceed the speed limit [49 CFR392.611). (Class II, Priority Action) (H-95-4) (Supersedes H-90-32)

to the Federal Highway Administration, the Professional Truck Driver Institute Of America, the American Trucking Associations, Inc., the Commercial Vehicle Safety Alliance, and the National Private Truck Council:

Develop and disseminate, in consultation with the U.S. Department of Transportation Human Factors Coordinating Committee, a training and education module to inform truckdrivers of the hazards of driving while fatigued. It should include information about the need for an adequate amount of quality sleep, strategies for avoiding sleep loss such as strategic napping, consideration of the behavioral and physiological consequences of sleepiness, and an awareness that sleep can occur suddenly and without warning to all drivers regardless of their age or experience. (Class II, Priority Action) (H-95-5)

to the American Trucking Associations, Inc., the National Private Truck Council, and the National Industrial Transportation League, the Independent Truck Owner Operators, the Owner-Operator Independent Driver's Association, and the International Brotherhood of Teamsters:

Urge your members to incorporate into their scheduling practices and procedures the results of the latest research on fatigue and sleep issues, particularly that an 8-hour continuous sleep need is the norm. (Class II, Priority Action) (H-95-6)

As a result of this study, the National Transportation Safety Board also reiterated the following safety recommendation to the Federal Highway Administration:

Require automated/tamper-proof on-board recording devices such as tachographs or computerized logs to identify commercial truck drivers who exceed hours-of-service regulations. (H-90-28)