substance use and driving – the state of knowledge

A DRIVING FORCE FOR SAFETY TRAFFIC INJURY RESEARCH FOUNDATION


Substance Use and Driving – The

state of knowledge

Ward VanlaarResearch AssociateTraffic Injury Research FoundationSmartrisk Learning SeriesTeleconferenceJanuary 29th, 2007


Overview Drinking and driving

RisksEpidemiological dataPublic perceptionSolutions

Driving under the influence of other substances

RisksEpidemiological dataPublic perceptionSolutions


Drinking and driving: Relative risk of crash


Slow but steady progress

Many countries including Canada experienced a

declinedecline in alcohol-related crashes in the

1980s and 1990s.


Persons Killed in alcohol involved Crashes

1296

1097 1070

986

906864 874 850

902

815

0

500

1,000

1,500

Number Killed

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004Source: Mayhew et al. 2006


The easy gains? Many experts agree that these declines can be traced primarily to socially responsible individuals:

they were drinking and driving they were drinking and driving less often.less often.

they were consuming less alcohol they were consuming less alcohol if they did drink and drive.if they did drink and drive.


Into the new millennium

Progress basically halted as we entered the new millennium. Same pattern holds

for all the reliable indicators we have.


The problem today

Despite progress, the problem persists at unacceptable levels.


The problem today

Given these statistics, it is not surprising to find that drinking and

driving is anything but uncommon.


The problem today We estimate that in the past year there were some 10.2 million10.2 million trips in Canada during which people drove when they thought they were over the legal limit.


Who is the problem ?

92.4% 92.4% of all those “impaired” driving trips were taken by

only 4.4%4.4% of all drivers.


A major problemThe Hard Core Drinking

DriverThe High-BAC Driver The Repeat OffenderThe Persistent Drinking

DriverThe Chronic Drunk Driver


Profile of the Hard Core

Often drink and drive -- this is frequent and routine behaviour for them.Usually have consumed large amounts of alcohol -- this is extremely dangerous for them and others.Many are alcohol dependent.


Drinking-driving decreasing or increasing?

19.3

16.716.1 15.8

17.8

14.7

17.5

0

2.5

5

7.5

10

12.5

15

17.5

20

Percent

1998 2001 2002 2003 2004 2005 2006Note: 1998 data include only drivers 18 years and over


Drinking-driving decreasing or increasing?

9.1

7.3

7.9

6.3

5.6

6.7

7.7

0

2.5

5

7.5

10

Percent

1998 2001 2002 2003 2004 2005 2006Note: 1998 data include only drivers 18 years and over


How concerned are Canadians?

29.8

32.1

47.1

60.5

65.9

66.1

68.7

73.2

73.9

75.5

88.0

0 10 20 30 40 50 60 70 80 90 100

Young Drivers

Older Drivers

Children Using ATV's

Drowsy Drivers

Cell Phones

Excessive Speeding

Distracted Drivers

Street Racing

Child Safety

Running Red Lights

Drinking Drivers

Percent Very or Extremely Serious Problem


Why are Canadians so concerned?

They think drinking and driving is very common; They believe drinking and driving comes with the highest possible risk; Their concern for drinking and driving is further compounded by their belief that drinking-drivers are not concerned about the risks they pose.


Solutions We need

measures that will: Protect the public Change behaviour


Solutions Many such effective programs have already been introduced in Canada (e.g., ignition interlocks, vehicle impoundment, treatment).


Summary The hard core should be a The hard core should be a priority for drinking-driving priority for drinking-driving

countermeasures.countermeasures.But by no means should this But by no means should this exclude our focus on “social exclude our focus on “social drinkers” or young drivers.drinkers” or young drivers.


Other substances and driving

Highly controversial and often confusing issue.Many claims; fewer solid facts.Near hysteria can surround the issue – societal ambivalence: alcohol (OK); drugs (not OK).Moral overtones – illegal (bad) versus legal (good) drugs.


Drugs and driving – complex issue

Drugs and driving is a much more complex issue than drinking and driving.Complexities account for shortcomings in knowledge and different interpretations of evidence.Public’s perceptions, attitudes and behaviour may be influenced by this complicated picture.


Why it is so complicated?Many different drugs; highly

complex chemicals.Different populations of users.Effects (pharmacodynamics) differ by drug and user.Testing for presence vastly more complex than testing for alcohol.


Five key questionsDo drugs impair skills/abilities

needed for safe driving?Do people actually use these drugs while they are driving?Are drivers who use them involved in collisions?Is there evidence that the presence of the drug caused the crash?How do people perceive the seriousness of drugs and driving?


Do drugs impair driving skills? Yes.Yes. Experimental studies show a wide range of drugs impair critical skills and abilities. Some have a potent impact particularly those with a sedative/hypnotic effect. Some have a moderate effect (cannabis); some are less likely to cause impairment (stimulants).


Do people use them and drive? Yes, but...Yes, but... Data on frequency and quantity of drug use in the driving population are sketchy. Best estimate is that about 10% of drivers are using impairing drugs. Marijuana is the most commonly reported/detected and is most commonly used by young males.


Do people use them and drive?2.4% of drivers in TIRF’s 2005 RSM indicated they had driven within 2 hours of using marijuana or hashish during past 12 months.Applied to the entire population, this corresponds to about 520,000 Canadians driving after using.There seems to be an increasing trend. In 2002: 1.5%; in 2004: 2.1%.


Characteristics of usersThose who reported using marijuana/hashish were:

more likely to be male (72% versus 55% among non-users)more likely to live in an urban setting (89% vs. 77%)less likely to be married (42% vs. 65%)more likely to have received a traffic ticket in past 12 months (40% vs. 10%)more likely to have been involved in a traffic collision (15% vs. 10%)


Characteristics of users

But…But…does the use of drugs increase risk taking or are users in general more likely to be risk takers?A considerable body of evidence shows that unhealthy lifestyle (e.g., smoking) and negative attitude toward health and safety are related to wide range of risky behaviours, including driving.


Characteristics of users

In 2005 RSM, users were more likely than non-users to “take a risk when driving just for fun” and “to drive over the posted speed limit”.Such findings make it difficult to establish a causal link between the impairing effects of cannabis and crash risk. Perhaps other factors such as willingness to take risk increase the likelihood of crash involvement, rather than the effects of cannabis.


Are drivers who use them involved in crashes?Yes.Yes. Overall incidence of drug detections among drivers killed or injured in road crashes is in the 14-17% range.Most commonly detected substances are:

cannabis (10-11% of cases); benzodiazepines (5-9% of cases) – class of drugs with hypnotic, anxiolytic, anticonvulsant, amnestic properties.


How many crashes are causedcaused by drug impairment?

Unknown,Unknown, because the evidence of the contribution of drugs to crashes is inconsistent and inconclusive.When drugs are detected in blood they are frequently found in combination with alcohol (as many as 84% of the cases with some drugs also test positive for alcohol).Distinguishing between the effects of the drugs and the characteristics of the users (e.g., risk taking among some users; reduced skills in general among elderly) is challenging.


Perceived seriousness of problem

Canadians are very concerned about issue of drugs and driving according to TIRF’s 2005 RSM.

87% perceive young drivers impaired by alcohol or drugs as a serious or extremely serious problem.61% perceive older drivers impaired by prescription medication as serious or extremely serious problem.By comparison, 86% perceive drinking drivers as serious or extremely serious.


Perceived seriousness of problem

Evidence suggests a high level of concern among Canadians.Evidence also suggests that people are not very good at estimating risk and incidence levels for driving after using drugs.Public may overestimate risk and incidence and attribute less concern to other important road safety issues (e.g., drinking and driving).Balanced messages to public are crucial.


SummaryMany drugs impair skills and abilities deemed important for the safe operation of a vehicle.Many of these drugs are used by people when they drive.Many of these drugs are found in drivers involved in collisions.The risks (contributory effects) are not well established. Public may not be able to appreciate problem in proportion to its true dimensions.On balance the evidence shows that the problem is by no means trivial even though it still is not well understood.


Action needsContinue research to clarify the magnitude and characteristics of the problem (e.g., EU-project DRUID).There is a need to verify whether young people are “substituting” drugs for alcohol to avoid detection/arrest.There is a need to study the perception of seriousness in more detail to determine whether Canadians attribute a proper level of concern to this issue.Continue efforts to produce a reliable chemical test for screening at roadside; cf. ROSITA-project (ROadSIde Testing Assessment; www.rosita.org).


Action needsIn absence of reliable chemical roadside test, alternative is to facilitate the collection of evidence of impairment – SFST.Also need a companion drug evaluation – DRE.


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