Driver fatigue is a factor in one in six truck crashes, says a study from Massey University's Sleep/Wake Research Centre.
The study, printed in the university's Research magazine, found accidents resulting from fatigue were three times more common than earlier estimates based on Land Transport Safety Authority crash reports.
The finding camefrom a study of truck accidents over 13 months.
The Commercial Vehicle Investigation Unit, whose officers are police trained in commercial vehicle operations, distributed 380 questionnaires to drivers involved in truck accidents in 2001 and 2002.
Driver fatigue was identified in three ways. First, the investigation unit officers indicated on the crash report if they thought driver fatigue was a factor in the crash.
Secondly, the drivers would tick a box on the questionnaire if they thought their own fatigue was a factor.
Finally, there was an analysis of each driver's sleep and duty history, to see if they were likely to have been affected by lack of sleep.
Of the 380 questionnaires sent out, 146 of the drivers completed them.
The study showed long driving hours, long duty hours and driving at specific times of the day were major factors in contributing to fatigue-related accidents.
Where the driver had been at the wheel for six hours, crashes were three times more likely to be fatigue-related. People driving between midnight and 8am were eight times more likely to have driver-fatigue crashes.
A Road Transport Forum spokesman said, because the study was based on the likely reasons for accidents, the actual number of fatigue-related accidents was probably lower.
He said drivers were required to take breaks, and truck companies should use an occupational health and safety guideline. It was down to operators to ensure drivers complied with the law and took appropriate breaks. However, he added: "Drivers do have their own lives and companies can't regulate what people do in their off times."
