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AAA Study: Blood THC Levels After Smoking Pot Are Useless In Defining 'Too High To Drive' (arstechnica.com)
An anonymous reader quotes a report from Ars Technica: Blood tests that try to quantify marijuana use are in fact useless at assessing how impaired a driver is, according to a study by the AAA Foundation for Traffic Safety. The study found that people with low blood amounts of THC -- or delta-9-tetrahydrocannabinol, the main psychoactive component of pot -- may still act as if they're really stoned. On the other hand, some people may have THC measurements off the charts yet still act normally. The finding is critical because several states have already set legal limits for the amount of THC a person can have in their blood while driving. AAA concluded that such limits are "arbitrary and unsupported by science, which could result in unsafe motorists going free and others being wrongfully convicted for impaired driving." The conclusion echoes that of other researchers that also noted no correlation between blood THC levels and impairment. Still, there is a need to deter people from smoking pot while driving, AAA argues, as it can impair driving. It recommends that until scientifically valid measures of impairments are put into place, law enforcement should use a combination of behavior and psychological tests to assess whether drivers who use marijuana are safe to drive.
long time alcoholic reaction times might still be reasonably ok even when way over the limit
Not really. What happens is that long time alcoholics become practiced at compensating for lousy reaction times.
Have gnu, will travel.
Problem solved.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
Yea, but blood alcohol limits had a LOT of science behind them before they became law. There is very good evidence showing reaction times are impaired a minimum of 50% at what are now legal blood limits even in the most tolerant drunk.
The first person with the money to fight one of these blood THC levels is going to win because the limit is entirely arbitrary and there is in fact no evidence whatsoever that THC impairs reaction time. They'd have as much luck trying to convict someone for having whipped cream in the blood. You can thank that DEA level 1 classification for that as no one has been able to do any real research on cannabis. In time we will find out but the only reason the courts allowed blood alcohol to be used against you was because there was a TON of research and good hard science documenting the connection between blood alcohol and reaction time.
The legislature can't make something legal to consume being in your blood illegal to drive unless they can demonstrate that it impairs your ability to drive. People have forgotten all the effort it took to get the courts to let blood alcohol content be actionable. Blood alcohol took almost a decade of court wrangling before it was eventually allowed as evidence of impairment. Hell maybe the supreme court will allow it because the most of the court loves jacked booted thugery but IMO the government should have to prove beyond a reasonable doubt that the substance impairs your driving ability to make it illegal to be on it while driving.
And even if they do cause an accident, they are going at a much slower speed than your typical drunk driver would be making the accident far less severe.
"Be particularly skeptical when presented with evidence confirming what you already believe." -
Oh, wait, do you know why alcohol and marijuana have an effect on the body? It's because the body is receptive to it's presence. Have you thought about why the body is receptive to these substances? It's because the body produces these same substances on its own.
This line of reasoning is flat out wrong in general. Plenty of receptors in the human body will react to many different molecules, including many that do not normally exist in the body but may have other molecules with similar shapes (or even just similar in one part that sticks out from the molecule).
Ethanol is a pretty simple chemical and appears in a lot of places in biology, including human metabolism. However, the CB1 and CB2 receptors that respond to THC are not in the body because the body has THC, but because of endocannabinoids like AG2 and others. And the body doesn't react the same, as different endocannabinoids will affect the two different receptors in a different ratio and affect additional receptors that THC doesn't.
Just as realistic as teenagers going on about how they are wonderful at multitasking.
Alcoholics are a mess at everything - very sad to watch it happen.
Here is an article on the subject from the Washington Post:
https://www.washingtonpost.com/news/the-watch/wp/2014/08/05/since-marijuana-legalization-highway-fatalities-in-colorado-are-at-near-historic-lows/
Here is source data:
https://www.codot.gov/library/traffic/safety-crash-data/fatal-crash-data-city-county
“Cannabis leads to a more cautious style of driving, [but] it has a negative impact on decision time and trajectory. [However,] this in itself does not mean that drivers under the influence of cannabis represent a traffic safety risk. … Cannabis alone, particularly in low doses, has little effect on the skills involved in automobile driving.”
... Both simulation and road trials generally find that driving behavior shortly after consumption of larger doses of cannabis results in (i) a more cautious driving style; (ii) increased variability in lane position (and headway); and (iii) longer decision times. Whereas these results indicate a 'change' from normal conditions, they do not necessarily reflect 'impairment' in terms of performance effectiveness since few studies report increased accident risk.
REFERENCE: Canadian Senate Special Committee on Illegal Drugs. 2002. Cannabis: Summary Report: Our Position for a Canadian Public Policy. Ottawa. Chapter 8: Driving Under the Influence of Cannabis
… Evidence of impairment from the consumption of cannabis has been reported by studies using laboratory tests, driving simulators and on-road observation.
REFERENCE: UK Department of Environment, Transport and the Regions (Road Safety Division). 2000. Cannabis and Driving: A Review of the Literature and Commentary. Crowthorne, Berks: TRL Limited.
“Overall, we conclude that the weight of the evidence indicates that:
There is no evidence that consumption of cannabis alone increases the risk of culpability for traffic crash fatalities or injuries for which hospitalization occurs, and may reduce those risks.
The evidence concerning the combined effect of cannabis and alcohol on the risk of traffic fatalities and injuries, relative to the risk of alcohol alone, is unclear.
It is not possible to exclude the possibility that the use of cannabis (with or without alcohol) leads to an increased risk of road traffic crashes causing less serious injuries and vehicle damage.”
REFERENCE: M. Bates and T. Blakely. 1999. “Role of cannabis in motor vehicle crashes.” Epidemiologic Reviews 21: 222-232.
“For each of 2,500 injured drivers presenting to a hospital, a blood sample was collected for later analysis.
There was a clear relationship between alcohol and culpability. … In contrast, there was no significant increase in culpability for cannabinoids alone. While a relatively large number of injured drivers tested positive for cannabinoids, culpability rates were no higher than those for the drug free group. This is consistent with other findings.”
REFERENCE: Logan, M.C., Hunter, C.E., Lokan, R.J., White, J.M., & White, M.A. (2000). The Prevalence of Alcohol, Cannabinoids, Benzodiazepines and Stimulants Amongst Injured Drivers and Their Role in Driver Culpability: Part II: The Relationship Between Drug Prevalence and Drug Concentration, and Driver Culpability. Accident Analysis and Prevention, 32, 623-32.
“Blood samples from 894 patients presenting to two Emergency Departments for treatment of motor vehicle injur[ies] … were tested for alcohol and other drugs.
… Based on alcohol and drug testing of the full range of patients … alcohol is clearly the major drug associated with serious crashes and greater injury. Patients testing positive for illicit drugs (marijuana, opiates, and cocaine), in the absence of alcohol, were in crashes very similar to those of patients with neither alcohol nor drugs. When other relevant variables were considered, these drugs were not associated with more severe crashes or greater injury.”
REFERENCE: P. Waller et al. 1997. Crash characteristics and injuries of victims impaired by alcohol versus illicit drugs. Accident Analysis and Prevention 29: 817-827.
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