Question: How do I treat a dark traffic signal at an intersection?
Answer: When a signal at an intersection loses power and there are no other traffic control devices (e.g., stop sign, yield sign, temporary signal, temporary sign) or police officers present at that intersection to provide direction, the intersection will be treated as a four way stop.
MCL 257.649 requires a driver approaching an intersection with a traffic control signal that does not clearly indicate the right of way or is malfunctioning to treat the intersection as a four-way stop by doing the following:
Stop at a clearly marked stop line, or, if there is no clearly marked stop line, stop before entering the crosswalk on the near side of the intersection, or, if there is no crosswalk, stop before entering the intersection.
Yield the right of way to all vehicles in the intersection or approaching on an intersecting road, if those vehicles create an immediate hazard when the driver is moving across or within the intersection.
Exercise ordinary care while proceeding through the intersection.
The “four-way stop” rules do not apply to the following:
An intersection that is controlled by a traffic control signal that is flashing yellow unless certain events occur, including, but not limited to, activation by an emergency vehicle.
A traffic control signal that is located in a school zone and is flashing yellow only during prescribed periods of time.
FAQ compliments of you the taxpayer and the MSP. Also please note the traffic light pictured has not gone out yet and is still working.
Question: I need a lawyer for a Traffic charge I got – Who should I call?
DISCLAIMER This website and/or post may contain re-posted content, opinions, comments, ads, third party posts, outdated information, posts from disgruntled persons, posts from those with agendas, private stuff, work related information, non work related information and general internet BS. Therefore…Before you believe anything on the internet regarding anything and everything – do your research on “Official Government and State Sites”, Call the Michigan State Police, Check the State Attorney General Website and Consult an Attorney – Use Your Brain. You’re on the internet.
To obtain your certified complete driving record, you can visit your local Secretary of State (SOS) office, request it online, or order it by mail. The cost for obtaining this record is $12.
To purchase a certified copy of your driving record online:
Create an account through MiLogin and authenticate your information on our website.
Your record will only be visible for 7 days.
Pay with a credit or debit card (additional fees apply) or e-check/bank account number.
Fee: $12
Ensure that you specifically request your certified complete record, as edited versions may not provide the necessary information. A complete record will have the number “42” on the second line of the upper left corner.
Once you have your driving record, carefully review everything below the section labeled “End of Record History.”
This section contains important and vital information about anything that must be addressed before your license can be reinstated. It includes details such as dates, locations, specific offenses, and suspension dates, if applicable.
If you see discrepancies on your driving record, you will need to contact the listed court for tickets and the listed police department for accidents. Corrections will then be sent to the Michigan Department of State to update your record. If you need to discuss other details of your record, call the Driver Records Activity Unit at 517-636-6406.
How long is my driving record available for viewing online?
The link for your electronic driving record in Michigan is only accessible for 7 days. During the seven-day period, you may view your electronic driver record as many times as you need to by logging in and choosing the option to View Transaction History. It is recommend you save your documents to your computer or device so that you may conveniently view the record at any time.
Do I need a certified copy of my driving record?
If you are purchasing your driving record for your own reference, you may not need a certified record. If you are purchasing a copy of your record for a court case, or for an employer, check with the person requesting the record to verify what type of record is needed and if it needs to be certified.
NOTE: All driving records purchased in Secretary of State offices are certified records.
Can I purchase a driving record for another person?
In most cases, Michigan residents can only purchase their own records. The following exceptions are allowed by law:
Commercial and governmental agency users The Michigan Department of State allows commercial and governmental users to obtain driver’s license, vehicle, mobile home, watercraft, and recreational vehicle records under certain specified conditions.
Driving Record Subscription Service The Driving Record Subscription Service provides organizations with the driving records of their employees on an annual basis, or whenever there are violations, restrictions, suspensions, or revocations posted to the driving record.
DISCLAIMER In a legal environment that continues to evolve, it is essential to stay informed and seek guidance from knowledgeable professionals. Before acting on any information you find on the internet, this website, any linked website, any referring website or any verbal or written information consult a licensed attorney. Contact Komorn Law today to discuss your case and learn how we can assist you in navigating the complexities of Michigan’s laws. Consult an Attorney – Remember you’re on the internet.
Driving is an essential part of everyday life for many Michigan residents. Whether it’s commuting to work, running errands, or simply exploring the state’s many attractions, having a valid driver’s license is crucial.
However, driving privileges in Michigan come with a set of rules, regulations, and requirements that every driver must adhere to. In this article, we will provide an overview of the driving privileges in Michigan, including the types of licenses and endorsements available, how to obtain and renew a license, the consequences of violating traffic laws, and the graduated driver licensing program for teen drivers.
Overview of Driving Privileges in Michigan
Introduction
Driving is a necessary part of life for many people in Michigan. However, driving privileges in Michigan require drivers to meet certain eligibility requirements, carry a valid license, and follow certain rules and regulations. It is essential to understand Michigan’s driving privileges and the processes involved in acquiring and maintaining a driver’s license.
Importance of Understanding Driving Privileges in Michigan
Knowing the requirements for driving in Michigan is vital to ensure safety on the roads and avoid legal consequences. Understanding Michigan’s driving privileges ensures that drivers are aware of what is expected of them when obtaining and maintaining a license. It is also essential to understand driving privileges to avoid penalties or revocation of driving privileges due to non-compliance with state laws.
If you or someone you know has been accused of a crime or DUI Hire experience and turn your defense into an offense. Komorn Law PLLC Call Now 248-357-2550
Types of Licenses and Endorsements in Michigan
Standard Michigan Driver’s License
The standard Michigan driver’s license allows individuals to operate passenger vehicles, light trucks, and vans. Michigan residents can obtain a standard driver’s license by passing a written test, a driving test, and demonstrating their ability to follow traffic laws.
Commercial Driver’s License (CDL)
Drivers seeking to operate commercial vehicles, such as large trucks or buses, must obtain a commercial driver’s license (CDL). CDL applicants must pass a series of written and driving tests specific to commercial driving.
Motorcycle Endorsement
Individuals who want to operate a motorcycle must obtain a motorcycle endorsement. This requires passing a written test and a skills test that demonstrates the ability to safely operate a motorcycle.
Applying for a Michigan Driver’s License
Eligibility Requirements
To apply for a Michigan driver’s license, applicants must be at least 16 years old, have a valid Social Security Number, and pass a vision screening and knowledge test.
Required Documents
Applicants must bring specific documents to the Secretary of State’s office to prove their identity, residency, and legal presence in the United States.
Written and Road Tests
Applicants must pass a written test and a practical road test to obtain a driver’s license. The written test covers traffic laws and safe driving practices, and the road test assesses the driver’s ability to operate a vehicle safely.
Michigan Driver’s License Renewal and Replacement Process
Renewal Requirements
Michigan drivers must renew their license every four years. To renew a driver’s license, drivers must pass a vision screening and pay a fee.
Renewal Options
Michigan drivers can choose to renew their license in person, by mail, or online. Renewal options may vary based on eligibility criteria and driving record.
Replacement Process
If a Michigan driver loses or damages their license, they can apply for a replacement at the Secretary of State’s office. To obtain a replacement license, drivers must present identification documents and pay a fee.
Michigan Driver’s License Suspension and Revocation
Reasons for Suspension and Revocation
In Michigan, your driver’s license can be suspended or revoked for a variety of reasons. Some of the most common reasons include driving under the influence (DUI), failing to pay child support, accumulating too many points on your driving record, driving without insurance, and being involved in a hit-and-run accident.
Consequences of Suspension and Revocation
When your license is suspended or revoked, you are not allowed to drive legally until it is reinstated. If you are caught driving while your license is suspended or revoked, you can face serious consequences, including fines, jail time, and even further license suspension or revocation. Additionally, having a suspended or revoked license can make it difficult to obtain car insurance or even keep your job if it requires driving.
Reinstatement Process
To reinstate your license in Michigan, you typically need to complete any necessary requirements related to the reason for your suspension or revocation, such as paying fines, completing a driver’s education course, or even attending a court hearing. Once you have met these requirements, you can then apply to have your license reinstated.
Michigan Points System and Traffic Violations
How the Points System Works
In Michigan, drivers accumulates points on their driving record for various traffic violations, such as speeding, running a stop sign, or driving under the influence. If you accumulate too many points within a certain period of time, your license can be suspended or revoked. The number of points you receive for each violation varies, with more serious violations resulting in more points.
Common Traffic Violations in Michigan
Some of the most common traffic violations in Michigan include speeding, reckless driving, driving with an expired license, failing to yield, and driving under the influence. It is important to follow all traffic laws and regulations to avoid accumulating points on your driving record.
Paying Fines and Contesting Tickets
If you receive a traffic ticket in Michigan, you typically have the option to pay the fine or contest the ticket in court. If you choose to contest the ticket, you will have the opportunity to plead not guilty and present evidence to support your case.
Michigan DUI and OWI Laws and Penalties
Legal Alcohol Content (BAC) Limits
In Michigan, it is illegal to operate a vehicle with a blood alcohol content (BAC) of 0.08% or higher. For drivers under the age of 21, the legal limit is lower at 0.02%.
Penalties for DUI and OWI in Michigan
If you are convicted of driving under the influence (DUI) or operating while intoxicated (OWI) in Michigan, you can face serious penalties, including fines, jail time, community service, and license suspension or revocation. The severity of the penalties depends on a variety of factors, such as your BAC, whether it is your first offense, and if anyone was injured or killed as a result of your actions.
License Suspension and Revocation for DUI and OWI
If you are convicted of DUI or OWI in Michigan, your driver’s license will be automatically suspended or revoked. The length of the suspension or revocation depends on the specific circumstances of your case, such as your BAC at the time of the offense and whether it is your first or subsequent offense.
Michigan Graduated Driver Licensing System for Teen Drivers
Overview of Michigan’s Graduated Driver Licensing (GDL) Program
Michigan’s Graduated Driver Licensing (GDL) program is designed to help teen drivers gain valuable experience and skills under certain restrictions before obtaining a full driver’s license. The program consists of three stages: level 1, level 2, and level 3.
GDL Requirements and Restrictions
During level 1 of the GDL program, teen drivers must be supervised by a licensed driver who is at least 21 years old and has held their license for at least 3 years. During level 2, teen drivers can drive alone, but with restrictions, such as not driving between midnight and 5 a.m. During level 3, teen drivers have full driving privileges.
GDL Progression and Full License Issuance
To progress through the GDL program, teen drivers must complete certain requirements, such as driving a certain number of hours and passing both a written and driving test. Once they have completed all requirements and reached level 3, they can apply for a full driver’s license.In summary, understanding the driving privileges in Michigan is key to maintaining a safe and lawful driving experience. By knowing the various types of licenses and endorsements, the application and renewal processes, and the consequences of violating traffic laws, drivers can ensure they are operating their vehicles legally and responsibly. Additionally, the graduated driver licensing program for teen drivers serves as an important tool for promoting safe driving habits and preparing new drivers for the road. By following the rules and regulations outlined in this article, drivers can protect their driving privileges and keep themselves and others safe on the road.
Frequently Asked Questions (FAQ)
What is the Michigan points system for traffic violations?
The Michigan points system assigns points to a driver’s record for certain traffic violations. The number of points assigned varies depending on the severity of the violation. If a driver accumulates too many points within a certain period, their license may be suspended or revoked.
What are the penalties for driving under the influence (DUI) or operating while intoxicated (OWI) in Michigan?
The penalties for DUI or OWI in Michigan vary depending on the circumstances of the offense, such as the driver’s blood alcohol content (BAC) level and whether there were any injuries or fatalities. Penalties can include fines, license suspension or revocation, community service, and even jail time.
Can I renew my Michigan driver’s license online?
Yes, most Michigan drivers are eligible to renew their driver’s license online through the Secretary of State’s official website. However, certain eligibility requirements must be met, such as having a valid Social Security number on file and not having any outstanding traffic violations or warrants.
What is the graduated driver licensing program in Michigan?
The graduated driver licensing (GDL) program in Michigan is a three-stage program designed to gradually introduce new drivers to the responsibilities of driving. The program includes a learner’s permit stage, an intermediate stage, and a full-privilege stage, with each stage gradually allowing more driving privileges and fewer restrictions. The GDL program is designed to help reduce the number of teen driver accidents and fatalities.
DISCLAIMER In a legal environment that continues to evolve, it is essential to stay informed and seek guidance from knowledgeable professionals. Before acting on any information you find on the internet, this website, any linked website, any referring website or any verbal or written information consult a licensed attorney. Contact Komorn Law today to discuss your case and learn how we can assist you in navigating the complexities of Michigan’s laws. Consult an Attorney – Remember you’re on the internet.
Walking – It’s still a right for now. Driving is another story. That is for the privileged. You must fight for that privilege when the system is in the process to take it away. Your best defense is a good offense. Komorn Law PLLC is the firm you hire when you want to go on the offense to put the system on defense. Yes that was some marketing we slipped in. Carry on…
Dangerous, negligent, or careless driving behavior can result in both serious legal consequences and the temporary or permanent loss of driving privileges.
License suspension
If a driver’s license is suspended, an individual’s driving privileges are temporarily withdrawn for a specific period and may be reinstated once the terms of the suspension are fulfilled. Because a driver’s license renewal transaction is required you must visit a Secretary of State Branch office to get your license reinstated.
License revocation
If a driver’s license is revoked, an individual’s driving privileges are terminated and can only be reinstated if the individual meets eligibility requirements and any conditions or terms set forth in a hearing facilitated through the Michigan Department of State.
Common causes for suspension or revocations
Six Points:
Manslaughter, negligent homicide, or other felony involving use of a motor vehicle
Operating under the influence of liquor or drugs
Failing to stop and give identification at the scene of a crash
Reckless driving
Unlawful bodily alcohol content of 0.08 or more
Refusal to take a chemical test
Fleeing or eluding a police officer
Four Points:
Drag racing
Operating while visibly impaired
Under age 21 with any bodily alcohol content
16 mph or more over the legal speed limit
Failure to yield/show due caution for emergency vehicles
Three Points:
Careless driving
Disobeying a traffic signal or stop sign or improper passing
11 through 15 mph over the legal speed limit
Failure to stop at railroad crossing
Failure to stop for a school bus or for disobeying a school crossing guard
Two Points:
Open alcohol container in vehicle
All other moving violations of traffic laws
Refusal of Preliminary Breath Test (PBT) by a driver under age 21
NOTE: Snowmobile and off-road vehicle (ORV) alcohol-conviction points are placed on a driver record and may result in licensing action against your driving privileges even though the violation happened while operating a snowmobile or ORV.
If you or someone you know has been accused of a crime, DUI or Drugged Driving. Call Komorn Law PLLC and turn your defense into an offense. Call Now 248-357-2550
Understanding the hearings process
Due to COVID-19 social distancing requirements there are NO LIVE (IN-PERSON) hearings being held at this time. Until further notice ALL OHAO hearings are being held via video conferences using Microsoft Teams.
If you have not already done so, please download the free Microsoft Teams app now. DO NOT REGISTER or LOGIN.
Review the Notice of Hearing to find the name of the hearing officer assigned to your hearing.
Locate the name of the assigned hearing officer on the list below.
Follow the link below the name of the assigned hearing officer that says (Follow this link to join the meeting) join as a guest using your first/last name.
Make sure to enable your camera and microphone icons found at the bottom center.
You must access this link from the device you intend to use.
This is a formal hearing, and you should be in a quiet location by yourself and have a clear table/area in front of you that is free from any documents.
PLEASE FOLLOW THE LINK BELOW AND SELECT THE HEARING OFFICER FROM YOUR LETTER
Drug and alcohol related suspensions and revocations
If your driver’s license was suspended or revoked due to a drug or alcohol related offense, you will want to familiarize yourself with the following programs and information as you work to restore your driving privileges.
Older drivers, drivers with numerous crash histories, drivers who may have been referred for health reasons after a license suspension, or as a result of a hearing may need to submit to a safe driving assessment and reexamination process.
Driver assessment
The privilege to drive is often taken for granted, but you may lose your privilege to drive for many reasons. The Secretary of State’s Driver Assessment Section is responsible for conducting driver reexaminations as authorized by the Michigan Vehicle Code. The purpose of a reexamination is to determine your ability to drive safely and if any licensing controls should be imposed.Michigan law allows for a driver reexamination based upon one or more of the following criteria:
You have received tickets while on probation.
The Secretary of State has reason to believe that you cannot operate a motor vehicle safely due to a mental or physical condition.
You have been involved in a fatal crash.
You have been involved in three or more traffic crashes within a two-year period where the crash report indicates you were at fault.
You have accumulated 12 or more points within a two-year period.
You have been convicted of violating the restrictions, terms, or conditions of your license.
Driver reexamination
Michigan law authorizes the Department of State to reexamine a driver when there is reason to believe the driver may be unable to operate a motor vehicle safely. The Department relies on information from law enforcement, medical personnel, Secretary of State branch staff, and concerned citizens, including family members, to identify unsafe drivers. The Department of State provides a form, called a Request for Driver Evaluation (DA-88), that can be completed and submitted to the Driver Assessment Section to request a review of an individual’s driving skills. This form is available at your local Secretary of State branch office or by clicking the link here.
Basic Driver Improvement Course
The Basic Driver Improvement Course program allows eligible drivers to take a refresher course of basic traffic safety principles. Drivers who successfully complete the BDIC through an approved sponsor can avoid points or ticket information from being reported to their insurance company.
BDIC eligibility
You will receive a letter in the mail if you are eligible for this program. You may be eligible if you were ticketed on or after December 31, 2010, and:
You have a valid Michigan, non-commercial license, with two or fewer points on your record,
The violation was not in a Commercial Motor Vehicle,
The violation was not a criminal offense,
The ticket you received is eligible (e.g., must be for three or fewer points, not for careless or negligent driving, etc.)
The course requires a minimum four hours of study before the first attempt to pass the final test. This refresher course can improve safety for all Michigan drivers. Eligible drivers have 60 days to arrange for and successfully complete the BDIC. The course completion deadline is listed on the notice of eligibility. Eligible drivers should begin the BDIC well before the deadline to ensure it can be completed before the deadline. The approved sponsor will notify the Secretary of State of course results.
Course options
BDIC are offered both online and in classroom settings by sponsors approved by the Michigan Department of State. Each sponsor uses a program that is based on a curriculum for which there is documented evidence from a federal, state, or local government agency of course effectiveness in reducing collisions, moving violations or both. Prices may vary.
The State of Michigan does not endorse any sponsor. Course sponsors are solely responsible for reporting results in a timely manner.
Please select your preferred method of taking your Basic Driver Improvement Course - Online or Classroom.
Frequently asked questions (FAQs)
What are the potential outcomes of my driving reexamination?
At the conclusion of your driver assessment reexamination, your license may be unaffected, or it may be restricted, suspended, or revoked depending on several factors. These factors include the type of violation or unsafe driving behavior involved, your driver record, and your willingness to comply with assessment recommendations and requirements.
License restrictions allow you to drive under certain terms and conditions that will be stated on your restricted license. A license suspension means that your driving privileges are taken away for a determined period of time, ranging from days to months. A license revocation means that you must wait one to five years before you are eligible to reapply for possible re-licensure. If your license is restricted, suspended, or revoked, you will be given your appeal rights and licensing reinstatement information.
What do I do if I need a reexamination of my driving skills?
If you are scheduled for a driver assessment reexamination, whether through a referral or mandated by the terms of a suspension, you will receive a notice telling you when and where to appear. Your reexamination will include time for the driver assessment analyst to review your driver record and discuss your driving behavior with you. You may be required to pass vision and knowledge tests as well as an on-road performance test. You may also be required to provide a medical or vision statement for review.
DISCLAIMER This post may contain re-posted content, opinions, comments, ads, third party posts, outdated information, posts from disgruntled persons, posts from those with agendas and general internet BS. Therefore…Before you believe anything on the internet regarding anything – do your research on Official Government and State Sites, Call the Michigan State Police, Check the State Attorney General Website and Consult an Attorney – Use Your Brain.
This Study was released in 2010 but has very good information.
Abstract
The prevalence of both alcohol and cannabis use and the high morbidity associated with motor vehicle crashes has lead to a plethora of research on the link between the two. Drunk drivers are involved in 25% of motor vehicle fatalities, and many accidents involve drivers who test positive for cannabis. Cannabis and alcohol acutely impair several driving-related skills in a dose-related fashion, but the effects of cannabis vary more between individuals than they do with alcohol because of tolerance, differences in smoking technique, and different absorptions of Δ9-tetrahydrocannabinol (THC), the active ingredient in marijuana. Detrimental effects of cannabis use vary in a dose-related fashion, and are more pronounced with highly automatic driving functions than with more complex tasks that require conscious control, whereas with alcohol produces an opposite pattern of impairment. Because of both this and an increased awareness that they are impaired, marijuana smokers tend to compensate effectively while driving by utilizing a variety of behavioral strategies. Combining marijuana with alcohol eliminates the ability to use such strategies effectively, however, and results in impairment even at doses which would be insignificant were they of either drug alone. Epidemiological studies have been inconclusive regarding whether cannabis use causes an increased risk of accidents; in contrast, unanimity exists that alcohol use increases crash risk. Furthermore, the risk from driving under the influence of both alcohol and cannabis is greater than the risk of driving under the influence of either alone. Future research should focus on resolving contradictions posed by previous studies, and patients who smoke cannabis should be counseled to wait several hours before driving, and avoid combining the two drugs.
1. Introduction
Accidents are the fifth leading cause of death in the US; nearly half are motor vehicle accidents, which according to the Fatality Analysis Reporting System (FARS) killed 38,588 people in 2006 alone.1 Motor vehicle accidents are the nation’s leading cause of death in those under 30.2 The contribution of drugs of abuse to this accident rate has attracted increasing attention in recent years because of the dramatic increase in drug use. In 2002, the National Survey on Drug Use and Health (NSDUH) estimated that 22 million Americans—9.4% of the population—have a substance use or dependence problem. As marijuana is the most commonly used drug of abuse, having been tried by 40% of the population,3 and is also smoked most commonly in the age group that also has the most road traffic accidents, the contribution of marijuana smoking to road traffic accidents is of great concern to both governments and clinicians responsible for counseling patients with substance abuse problems. Moreover, given the paucity of data supporting marijuana’s acute toxicity, the most serious possible consequence of acute cannabis use is a road traffic accident from driving while intoxicated.4 The very high cost of crashes, both human and financial, underlines the importance of understanding the extent to which marijuana use contributes to such accidents. The purpose of this paper is to review the scientific evidence on the effects on driving while intoxicated with marijuana and contrast this with the effects of alcohol intoxication.
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2. Epidemiology of marijuana smoking and road traffic accidents
The rising prevalence of cannabis use, its increased availability and potency,5 lower prices, widespread social tolerance, and earlier age of onset of use have combined to increase the number of users and hence the number of people subject to cannabis use disorders.6 Peak initiation is at age 18, and ten years later, 8% of users are marijuana-dependent.7 Most cannabis use is intermittent and time-limited, however; users generally stop in their mid-to-late 20s, and only a small minority continue in daily use over a period of years.8
Young people also account for a disproportionate number of road traffic accidents. According to the National Center for Statistics and Analysis, the fatality rate for teenagers is four times that of drivers age 25 to 69, and drivers under age 25 account for a quarter of all traffic fatalities.9 Risk factors for having a fatal traffic accident include being a young man, having psychological characteristics such as thrill-seeking and overconfidence, driving at excessive speed, driving late at night, failing to wear a seatbelt, and lacking familiarity with the vehicle.10 The risk factors for adolescent marijuana use are somewhat overlapping—delinquency (vandalism, shoplifting, joyriding etc.), poor school performance, and substance use by self and peers.11
The National Highway Transportation Safety Administration (NHTSA) reported that in 25% of all motor vehicle crash fatalities, the driver had a blood alcohol concentration (BAC) of 0.01 g/dL (one eighth the legal limit) or greater, and in 21-year-old drivers, that figure rose to 39%.12 Drivers with a previous DWI (“Driving While Impaired”) conviction were responsible for 7.2% of all crashes involving alcohol.
In comparison, the percentage of road traffic accidents in which one driver tested positive for marijuana ranges from 6% to 32%.13, 14 In one study, 9.7% of cannabis smokers reported having driven under the influence in the previous year; those who did drove while intoxicated an average of 8.1 times during the year.15 Among those who seek treatment for cannabis problems, more than 50% report having driven while “stoned” at least once in the previous year.16, 17
3. Studies relevant to marijuana and smoking
Three types of studies are generally performed to help assess the risk that smoking marijuana may increase the probability of having a fatal traffic accident. The first are cognitive studies that measure the effects of smoking marijuana on cognitive processes that are considered to be integral to safe driving. The second are experimental studies on the collision risk of people under the influence of marijuana. The third are descriptive and analytic epidemiological studies on the relationship between cannabis use and accidents, usually performed through drug testing of injured drivers.
3.1 Cognitive studies
Attentiveness, vigilance, perception of time and speed, and use of acquired knowledge are all affected by marijuana;18–21 in fact, a meta-analysis of 60 studies concluded that marijuana causes impairment in every performance area that can reasonably be connected with safe driving of a vehicle, such as tracking, motor coordination, visual functions, and particularly complex tasks that require divided attention,22 although studies on marijuana’s effects on reaction time have been contradictory.23 Similar conclusions have been reached by other reviewers.2 Worse still, marijuana and alcohol, when used together, have additive or even multiplicative effects on impairment.24 Consequently, on the basis of cognitive studies, it seems reasonable to propose that smoking marijuana may increase the risk of having a fatal traffic accident.
Alcohol at 0.75 g/kg (slightly less than four standard drinks) causes high levels of impairment in psychomotor performance and medium-to-high levels of impairment in such tasks as critical flicker fusion and short-term memory.25 Alcohol impairs pursuit tracking, divided attention, signal detection, hazard perception,26–28 reaction time, attention, concentration, and hand-eye coordination.29, 30
Alcohol also reduces the perceived negative consequences of risk-taking,31 which can increase willingness to take risks after drinking,32 the amount of risk-taking behavior while driving, even at low alcohol doses,33 and the incidence of road traffic accidents while driving drunk.34, 35 However, there is considerable variability in the effects that alcohol can have on people—the same dose may have different effects not only on different individuals, but also in the same individual on different occasions, because of other factors such as gender, body mass index, age, drinking habits, time of day, stomach contents, genetics, stage of the menstrual cycle, and environmental factors.36
3.2 Experimental research (driving and simulator studies)
Experimental research measures the potential risk of an accident using a driving simulator or driving course.
3.2.1 Studies that do not show impairment
Surprisingly, given the alarming results of cognitive studies, most marijuana-intoxicated drivers show only modest impairments on actual road tests.37, 38 Experienced smokers who drive on a set course show almost no functional impairment under the influence of marijuana, except when it is combined with alcohol.39
Many investigators have suggested that the reason why marijuana does not result in an increased crash rate in laboratory tests despite demonstrable neurophysiologic impairments is that, unlike drivers under the influence of alcohol, who tend to underestimate their degree of impairment, marijuana users tend to overestimate their impairment, and consequently employ compensatory strategies. Cannabis users perceive their driving under the influence as impaired and more cautious,40 and given a dose of 7 mg THC (about a third of a joint), drivers rated themselves as impaired even though their driving performance was not; in contrast, at a BAC 0.04% (slightly less than two “standard drinks” of a can of beer or small 5 oz. glass of wine; half the legal limit in most US states), driving performance was impaired even though drivers rated themselves as unimpaired.41 Binge drinkers are particularly likely to rate themselves as unimpaired, possibly because they tend to become less sedated by high doses of alcohol.42
This awareness of impairment has behavioral consequences. Several reviews of driving and simulator studies have concluded that marijuana use by drivers is likely to result in decreased speed and fewer attempts to overtake, as well as increased “following distance”. The opposite is true of alcohol.43 One review of eight driving simulator studies and seven on-road studies44 found that cannabis use was associated with either poor lane control41, 45–48 or slower driving that successfully maintained lane control.49–51 In seven of ten studies cited, cannabis use was associated with a decrease in driving speed despite explicit instructions to maintain a particular speed, whereas under the influence of alcohol, subjects consistently drove faster. Two simulator studies showed that the tendency to overtake was decreased with cannabis use but increased with alcohol.52, 53 One simulator study and two on-road studies examining car-following behavior concluded that cannabis smokers tend to increase the distance between themselves and the car in front of them.41, 45 Other studies have found no adverse effects of marijuana use on sign detection,49 a sudden lane-changing task,43 or the detection of and response to hazardous events.48
3.2.2 Studies that show impairment
Not all deficits can be compensated for through the use of behavioral strategies, however. Both alcohol and marijuana use increase reaction time and the number of incorrect responses to emergencies.43 Drivers under the influence of marijuana were not able to compensate for standard deviation of lateral position (SDLP, a measure of staying within lane), which increased with increasing doses of THC. This is a measure that is not subject to conscious compensatory mechanisms in the way that other aspects of driving are. Other studies have found poorer monitoring of the speedometer under the influence of marijuana,54 increased decision time when passing,52 increased time needed to brake when a light suddenly changes,55 and increased time to respond to a changing light45, 56 or sudden sound.57 Drivers also crashed more frequently into a sudden obstacle on a high dose of marijuana, although this did not happen at a low dose.45
Meta-analyses of over 120 studies have found that in general, the higher the estimated concentration of THC in blood, the greater the driving impairment, but that more frequent users of marijuana show less impairment than infrequent users at the same dose, either because of physiological tolerance or learned compensatory behavior. Maximal impairment is found 20 to 40 minutes after smoking, but the impairment has vanished 2.5 hours later, at least in those who smoke 18 mg THC or less (the dose often used experimentally to duplicate a single joint).58, 59
With increasing doses of alcohol, however, there is general dose-dependent lowering of both sustained attention and overall attentional capacity, with consequently more concentration paid to the main component of a complex skill (steering, for example), and less and less attention paid to secondary tasks (such as speed or driving skill). Functional imaging on the effects of increasing doses of alcohol up to a BAC of 0.08% in simulated driving has demonstrated that orbitofrontal areas (subsuming judgment) and motor areas are affected first, then cerebellar areas controlling coordination show functional deterioration, and finally, at high doses, global cognitive networks and simulated driving performance are impaired.60
Interestingly, three reports indicate that chronic marijuana smokers are less susceptible to impairment from alcohol on some measures compared with nonsmokers or infrequent smokers. As far back as 1970, Reese Jones noticed that alcohol’s effects were diminished in heavy cannabis smokers.61 A subsequent study showed that regular cannabis smokers demonstrate less of a decrement in peripheral signal detection under the influence of alcohol than do infrequent users,62 and a later study still found that regular cannabis users given alcohol alone showed less of a decrement in tracking accuracy and dizziness ratings than infrequent users given the same alcohol dose.63 The reason for this is unclear, but is hypothesized to result from either pharmacological or behavioral cross-tolerance between marijuana and alcohol.
3.2.3 Summary of experimental studies
It appears that cannabis use may impair some driving skills (automatic functions such as tracking) at smoked doses as low as 6.25 mg (a third of a joint), but different skills (complex functions that require conscious control) are not impaired until higher doses, and cannabis users tend to compensate effectively for their deficits by driving more carefully. Unexpected events are still difficult to handle under the influence of marijuana, however, and the combination of low-dose alcohol and low-dose cannabis causes much more impairment than either drug used alone.48, 64, 65 Alcohol appears to impair tasks requiring cognitive control more than it does automatic functions, whereas marijuana at a comparable dose impairs automatic functions more than those requiring cognitive control. Together, the effects on impairment are additive and may even be synergistic. Chronic marijuana smokers are less impaired by both alcohol and marijuana than would be expected, however.
3.3 Epidemiologicalstudies
One weakness of driving studies is that subjects are aware of being observed and assessed, so such studies are generally a better measure of what drivers are capable of doing rather than what they actually do. Epidemiological studies attempt to assess the actual risk that a driver may cause an accident under the influence of a drug, relative to that of a sober person driving under similar conditions. The relative risk is expressed in the form of an “odds ratio” (OR), which is the multiplier for the increased accident risk from driving under the influence of marijuana. Two approaches are taken. The first is culpability studies, which classify drivers who have crashed according to their degree of responsibility for the crash, then compare drug use in each category. If there is greater use of the drug in those culpable for crashes, then the drug is judged to be responsible for a greater crash risk. The second is case control studies. We will discuss both in turn.
3.3.1 Culpability studies
3.3.1.1 Studies that do not show culpability
Some reviewers have concluded that there is no evidence that cannabis alone increases the risk of culpability for crashes, and may actually reduce risk.66 Drummer’s review of blood samples of traffic fatalities in Australia found that drivers testing positive for marijuana were actually less likely to have been judged responsible for the accident.67 Several other studies have found no increase in crash risk with cannabis.68–70 Williams’ California study of 440 male traffic accident deaths found that while alcohol use was related to crash culpability, cannabis use was not.71 Terhune’s study of 1882 motor vehicle deaths calculated an OR of 0.7 for cannabis use, 7.4 for alcohol use, and 8.4 for cannabis and alcohol use combined.68 Lowenstein and Koziol-McLain’s study of 414 injured drivers admitted to a Colorado E/R found an OR of 1.1, indicating that marijuana use was not associated with increased crash responsibility.72 Drummer’s later and more extensive ten-year study of 3400 traffic fatalities in three Australian states found that drivers with blood THC levels less than 5 ng/mL, and those with only carboxy-THC present (THC-COOH, a metabolite that is excreted in the urine for weeks and is thus more likely to indicate past use than current use), had an OR of 1.0, but those with serum levels greater than 5 ng/mL had an OR of 6.6, the same as that for a BAC of 0.15%. In all 30 cases in this study in which one driver had a serum level of THC greater than 10 ng/mL, that driver was judged to have been responsible for the accident. When marijuana was combined with alcohol, the risk was higher still.73 A later reanalysis of the same data that adjusted for the age and sex of the fatalities found that OR of crashing for cannabis use alone dropped to 0.6 (not significantly different from 1.0), versus 7.6 for alcohol.66 Laumon’s study of 10,748 French motor vehicle fatalities found that although rates of alcohol and cannabis intoxication were similar (nearly 3%), ten times as many crashes were associated with alcohol as with cannabis; however, investigators noted a dose-dependent effect on OR with increasing THC serum levels, confirming Drummer’s observation by calculating an OR of 4.72 for THC levels greater than 5 ng/mL.74 Longo’s large, well-known study of hospitalized injured drivers in South Australia showed few adverse effects of cannabis on crash risk, although there was a slightly increased risk of crashing with higher THC concentrations and a slightly lower risk with lower concentrations.75
What 5 ng/mL means in terms of actual impairment is hard to calculate, as THC levels in the blood peak quickly following inhalation then decrease rapidly according to complex pharmacokinetics, making it almost impossible to extrapolate backwards from the concentration of THC at the time of the blood test to the concentration at the time of the traffic accident. Some insight can be gained from Jones’ study of 1276 Swedish motorists arrested for DUI with blood tests positive for THC alone, which revealed an average THC blood level of 3.6 ng/mL at the time of testing.76 A similar Swiss study of 440 DUI suspects who also were positive for only THC found average blood concentrations of 5.0 ng/mL at the time of testing, indicating that a residual level of 5 ng/mL does appear to correlate with observable driving impairment earlier.77 The Swedish study also found that, of the 291 DUI arrestees who were positive for both THC and alcohol, the average THC blood level was only 2.3 ng/mL, again suggesting that lower levels of THC, when combined with alcohol, are sufficient to cause obvious impairment.76
Methodological problems often can make culpability studies hard to interpret, however. Since no study has ever shown an increased risk of road accidents among frequent marijuana smokers who are not intoxicated at the time that they drive, a positive urine test that measures levels of the long-lasting metabolite carboxy-THC but not the active ingredient THC is insufficient to classify a driver as intoxicated, as such a measure will include in the marijuana group unimpaired people who have smoked only in the past and thus artificially depress the OR.78 The Colorado study that found that marijuana use was not associated with increased crash responsibility used urine toxicology to assess drug use, so likely suffered from this limitation.72 Sampling delays in excess of an hour can cause an underestimation of THC concentration in the blood of injured drivers who test positive for marijuana, possibly explaining Longo and others’ failure to find adverse effects.
Alcohol levels, which have linear pharmacokinetics, are easier to back-calculate to the time of the accident, and are consistently linked with increased culpability in crashes.71, 75 Moreover, whereas CNS levels of alcohol, which moves easily throughout the body with little difference in concentration between compartments, can be approximated with a good degree of accuracy through measuring blood or breath levels, the same is not true of THC, which is highly lipophilic and concentrates preferentially in adipose tissue. Consequently, experimental studies have shown that functional impairment (which reaches a maximum an hour after smoking) lags behind THC blood level (which peaks within minutes and decreases rapidly thereafter).79 (Figure 1) This makes it much harder to generate blood level versus impairment curves for marijuana than it is for alcohol.
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