Tiredness! a natural explanation to The Grand Rapid "DIP"

Cannabis and crash responsibility while driving below the alcohol per se legal limit

There is a growing interest in how extensively the use of marijuana by drivers relates to crash involvement. While cognitive, lab-based studies are consistent in showing that the use of cannabis impairs driving tasks, epidemiological, field-based studies have been inconclusive regarding whether cannabis use causes an increased risk of accidents. There is ample evidence that the presence of cannabis among drivers with a BAC≥0.08g/dL highly increases the likelihood of a motor vehicle crash. Less clear, however, is the contribution of cannabis to crash risk when drivers have consumed very little or no alcohol. This effort addresses this gap in knowledge. We took advantage of a unique database that merged fatal crashes in the California Statewide Integrated Traffic Records System (SWITRS) and the Fatality Analysis Reporting System (FARS), which allows for a precise identification of crash responsibility. To account for recent increase in lab testing, we restricted our sample to cover only the years 1993-2009. A total of 4294 drivers were included in the analyses. Descriptive analyses and logistic regressions were run to model the contribution of alcohol and drugs to the likelihood of being responsible in a fatal crash. We found evidence that compared with drivers negative for alcohol and cannabis, the presence of cannabis elevates crash responsibility in fatal crashes among drivers at zero BACs (OR=1.89) and with 0<BAC<0.05g/dL (OR=3.42), suggesting that emphasis on curbing impaired driving should not be solely focused on heavy-drinking drivers. Data limitations however caution about the generalizability of study findings. Special efforts to understand the effect of cannabis on fatal crashes, in particular in the absence of alcohol, are needed.

Sleep deprivation does not mimic alcohol intoxication on field sobriety testing

Previous research shows that sleep deprivation (SD) produces cognitive impairment similar to that caused by alcohol intoxication. Individual studies suggest that SD also causes deficits in motor skills that could be mistaken for intoxication. Consequently, SD often is used as a defense when an impaired driver is charged with driving while intoxicated. Twenty-nine adult subjects participated in two test sessions each, one after a full night's rest and the other after wakefulness of at least 24 h. Subjects consumed prescribed amounts of alcohol during each session. Law enforcement officers conducted field sobriety tests identical to those with which a driver would be assessed at roadside. Researchers also measured clinical responses of visual function and vital signs. The presence and number of validated impairment clues increase with increasing blood alcohol concentration but not with SD. Thus, SD does not affect motor skills in a manner that would lead an officer to conclude that the suspect is intoxicated, unless intoxication also is present.

Convicted of fatigued driving: who, why and how?

Fatigue is a major cause of road traffic accidents. However, due to the blurred concept of fatigue and the lack of reliable testing devices (cf. the breath analyzer for alcohol levels), it is extremely difficult to incorporate fatigue in operationalized terms into either traffic or criminal law. Even though the Finnish Road Traffic Act explicitly forbids driving while tired, it is done only on a general level among other factors (sickness, etc.) that impair a driver's fitness to drive (Article 63). The present study was done to investigate the circumstances of fatigue driving offenses. From the Finnish Vehicle Administration driver record database we extracted all drivers (N=768) punished under Article 63 from 2004-2005. Of these drivers, 90.4% committed a fatigue-related traffic offense. Accidents, predominantly single vehicle, were the most common (92.5%) consequence of fatigued driving. Although fatigue-related accidents are thought to be serious, our data shows that most of the accidents (81.6%) did not involve personal injuries. Almost every twentieth driver was punished because his vehicle was drifting on the road. The presence of alcohol or drugs was noted in 13% of the cases. Only 3.1% of the punished drivers officially denied being tired or falling asleep. Young men (< or =35 yrs) represented 50% of all punished drivers. Time of day and seasonal effects were clear in this data. This study shows that even without a reliable fatigue detector and unambiguous criteria for recognizing the contribution of fatigue to accident causation, Finnish police and the courts punish a significant number of drivers every year on the basis of fatigue.

Sleepiness among night-time drivers: relationship to blood alcohol concentration and other factors

OBJECTIVE

The study aimed to explore the distribution and correlates of subjective sleepiness among the general night-time driving population.

METHODS

The survey took place in three British Columbia communities in June 2003 between 21:00 hours to 03:00 hours. Sites and vehicles were selected randomly. Surveyors obtained information on several demographic and situational variables including self-assessed degree of sleepiness and self-reported hours asleep and awake, as well as an objective measure of blood alcohol concentration obtained from a hand-held breath-testing device.

RESULTS

The total compliance rate among intercepted drivers was 85%. Among the 2335 drivers responding to the questionnaire, 68.4% indicated that they were wide awake, 27.6% were somewhat sleepy, and 4.1% were very sleepy. Logistic regression quantified the independent contributions of the various factors to subjective sleepiness. Male drivers with positive blood alcohol concentrations under 50 mg% were more likely to report feeling sleepy than those with either higher or with zero blood alcohol concentration. Greater relative risk of sleepiness was also associated with being female, being under age 55, and advanced hour of night. Driving with passengers of the same gender was associated with lower reported sleepiness.

CONCLUSIONS

A substantial proportion of night-time drivers are driving while sleepy, especially at late night and early morning hours. The combination of alcohol and sleepiness compounds impairment in experimental studies and deserves greater attention in crash risk studies and as a topic for public education and awareness.