National Highway Traffic Safety Administration
NHTSA Research onImpaired Driving
Heidi ColemanChief, Behavioral Research
NHTSA Office of Behavioral Safety Research
Safer Drivers. Safer Cars. Safer Roads.
• The prevalence of impaired driving– National Roadside Surveys; Washington Roadside Survey
• Impairment due to the use of alcohol and other drugs– Inhaled Cannabis Study
• The crash risk of impaired driving– Crash Risk Study
• Strategies to reduce impaired driving – Laws and Policies– Law Enforcement and Criminal Justice Strategies– Assessment, Monitoring and Treatment– Prevention, Communication and Outreach
Impaired Driving Research – Key Questions
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National Roadside Survey (NRS)
• Research Note published February 2015
• Full report (3 volumes) in review Methodology Alcohol Results Drug Results
• Hope to publish reports in 2015
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• Four decades of National Roadside Surveys– 1973, 1986, 1996 (alcohol only)– 2007, 2013-2014 (included also drugs)
• Well developed methodology– Nationally-representative sample of drivers– Reviewed and approved by Institutional Review Board– Voluntary and anonymous – About 10,000 drivers in 300 locations across the nation
• Nighttime weekend sample– Daytime comparison
NRS - Overview
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60 sites across the country, representing the U.S.• Five “shifts” each weekend; five locations at each site:
– Fridays• 9:30 am – 11:30 am or 1:30 pm – 3:30 pm• 10:00 pm – midnight• 1:00 am – 3:00 am
– Saturdays• 10:00 pm – midnight• 1:00 am – 3:00 am
NRS - Data Collection
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• Drivers guided to survey bay• Breath Test (PBT)• Alcohol Use Disorder (AUD) questions• Drug use questions • Oral fluid collection with Quantisal device ($10)• Blood sample collection by phlebotomist ($50)
NRS - Procedure
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NRS - Team Sets Up
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NRS - As Drivers Approach
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NRS - First Thing Drivers See
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NRS - Data Collection Underway
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NRS - Data Collection (continued)
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NRS - We’re Ready for Every Situation
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NRS 2013-2014 – Participation
Number of Participants and Participation Rates in the 2013-2014 NRS
DriversParticipants
N %
Eligible and Entered Site 11,100 100.0%
Breath Test 9,455 85.2%
Oral Fluid Test 7,881 71.0%
Blood Test 4,686 42.2%
Oral Fluid and/or Blood 7,898 71.2%
Safer Drivers. Safer Cars. Safer Roads.
NRS 2013-2014 – Alcohol Results
Percentage of Weekend Nighttime Drivers by BrAC Category in the Five National Roadside
Surveys22.3
17.6
9.27.9
5.26.1
3 3.42.3 1.6
7.5
5.44.3
2.2 1.5
0
5
10
15
20
25
1973 1986 1996 2007 2013-2014
Perc
enta
ge o
f Driv
ers
Year of Survey
BrAC .005-.049
BrAC .050-.079
BrAC .08+
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Data Collection Time Period
% Alcohol Positive (%BrAC > 0.005)
% BrAC > 0.08
Friday Daytime 1.1% 0.4%
Friday and Saturday Nighttime 8.3% 1.5%
NRS 2013-2014 – Alcohol Results
Alcohol Prevalence by Data Collection Period and BrAC in the 2013–2014
NRS
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NRS 2013-2014 – Drug Results
Overall Drug Prevalence by Data Collection Period and Type of Test in the 2013–2014 NRS
Time of Day
% Drug-PositiveOral Fluid Test
% Drug-Positive
Blood Test
% Drug-PositiveOral Fluid and/or
Blood Test
Weekday Daytime 19.0% 21.6% 22.4%
Weekend Nighttime 19.8% 21.2% 22.5%
Drug-positive = over-the-counter, prescription, and illegal.Presence does not equal impairment.
Safer Drivers. Safer Cars. Safer Roads.
NRS 2013-2014 – THC Results
Weekend Nighttime Prevalence of THC in 2007 Compared to 2013-2014 Comparable Data
2007 2013-2014 Comparable Data
Oral FluidTest
BloodTest
Oral Fluid and/or Blood
Test
Oral FluidTest
BloodTest
Oral Fluid and/or Blood
Test
N % N % N % N % N % N %
438 7.7% 234 7.6% 499 8.6% 597 11.3% 332 11.7% 663 12.6%
Safer Drivers. Safer Cars. Safer Roads.
Summary of NRS 2013-2014 Results
• Alcohol use by drivers continues to decline
– Decrease by more than three-quarters since 1973
– Decrease by nearly one-third since 2007– Policies and programs appear to be working
• Drug use increasing – Prescription and over-the-counter use up
slightly – Illegal use up significantly – Marijuana use up by nearly 50% since 2007
Safer Drivers. Safer Cars. Safer Roads.
Crash Risk Study
• Research Note published February 2015
• Full report in review• Hope to publish report in
2015
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• Previous studies to estimate Crash Risk of Alcohol– Borkenstein (1974); NHTSA (Blomberg, 2005)
• Sought to estimate Crash Risk of Alcohol and Drugs
• “Case-control” methodology– Comparison of an experimental case (driver in a crash)
to a comparison control case (driver not in a crash)
– Trusted methodology; precise design; expensive and time-consuming
– In a site where enforcement, hospitals, local gov’t, etc. would fully cooperate and participate – Virginia Beach, VA
Crash Risk Study - Background
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• Sample size of 3,000 crash-involved drivers• Sample size of 6,000 control drivers• Matched as best we can based on –
– Same stretch of road, direction of traffic– Same day of week, time of day
• Perfect? No. • Most carefully designed study to date? YES.
Crash Risk Study - Study Design
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• When a crash was reported….– Research Team responded
• Team = Virginia Beach Police Office; PIRE Researcher/Phlebotomist
– Once scene secured and everyone safe, Officer asked the driver if they would be willing to talk to a Researcher
• If yes – study began• If no – thanks anyway
• Like NRS, the study was:– Voluntary, anonymous, driver can choose to stop at any
time
• Returned the following week for control drivers
Crash Risk Study - Protocol
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For both crash-involved drivers and control drivers:
• Asked questions about drinking, driving, drinking and driving, and drug use
• Asked drivers to provide:– Breath sample– Oral fluid sample ($10)– Blood sample ($50)
• Statistical analysis used to match crash to control cases
Crash Risk Study – Protocol (cont)
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Crash Risk Study
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Study continues
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Crash Risk Study - Participation
Crash Control
Eligible Drivers 3,887 7,397
Agreed to Participate 3,682 (94.7%) 7,176 (97.0%)
Breath sample 3,393 (87.3%) 7,079 (95.7%)
Oral Fluid or Blood 3,196 (82.2%) 6,935 (93.8%)
Safer Drivers. Safer Cars. Safer Roads.
Crash Risk Study Results – Alcohol Crash Risk
0.00
0.01
0.01
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
0.11
0.12
0.13
0.14
0.15
0.16
0.17
0.18
0.19
0.20
0.21
0.22
0.23
0.24
0.25
+0
5
10
15
20
25
30
35
40
All Driver Breath Samples Drug Negative Drivers Blomberg et alBAC
Re
lativ
e R
isk
(Re
lativ
e to
BA
C =
0.0
0)
Alcohol Crash Risk Adjusted for Age and Gender
Safer Drivers. Safer Cars. Safer Roads.
Crash Risk Study Results – Drug Crash Risk
• Significant findings (p value ≤ .01) for two types of drugs– THC (marijuana)– Illegal drugs
Drug of Interest
Unadjusted Odds Ratio
P Value
THC (Marijuana) 1.25 0.01
Sedatives 1.30 0.06
Narcotic Analgesics
1.15 0.26
Antidepressants 1.06 0.75
Stimulants 1.01 0.40
Illegal Drugs 1.21 0.01
Legal Drugs 1.07 0.43
Unadjusted Odds Ratios between Drug Class Use and Crash Risk
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Crash Risk Study Results – Drug Crash Risk
Drug of Interest
Adjusted Odds Ratio
95% CI*
P
Value
THC (Marijuana) 1.05 0.86 – 1.27 0.65
Antidepressants 0.87 0.57 – 1.32 0.51
Narcotic Analgesics
1.14 0.85 – 1.51 0.39
Sedatives 1.27 0.93 – 1.75 0.13
Stimulants 0.94 0.72 – 1.22 0.64
Illegal Drugs 1.04 0.88 – 1.23 0.65
Legal Drugs 1.03 0.84 – 1.27 0.79
Adjusted Odds Ratios between Drug Class Use and Crash Risk(adjusted for demographics, e.g., age, gender)
• When adjusted for factors that we know are associated with crash risk (e.g., age, gender)
• No significant findings• Age/gender accounted
for elevated THC and illegal drug risk
Safer Drivers. Safer Cars. Safer Roads.
• Study confirms elevated risk based on alcohol• Study does not demonstrate elevated risk based on drugs• Consistent with previous well controlled studies• However, study does not indicate that drug use by drivers is risk-
free• In some situations, drugs (other than alcohol) can seriously impair
driving ability and increase crash risk
• Due to increased prevalence of drugs (NRS), further monitoring and research is warranted
Crash Risk Study - Summary
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• Examine the Effects of Inhaled Cannabis on Driving Performance
• Expert Panel on Impact of Legalizing Marijuana on the DWI System (NCREP project)
• Washington State – Roadside Survey of Alcohol and Drugs (THC)
• Evaluation of Oral Fluid Drug Testing Devices (Allere; Drager)
• Evaluation of the Advanced Roadside Impairment Driving Enforcement (ARIDE) Curriculum
Other Drugged Driving Research
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• DWI Court Survey (ongoing)
• Feasibility of Ignition Interlocks on Motorcycles (pending agency review)
• Use of Interlock Data (pending agency review)
• Feasibility of Voluntary Interlock Program for Teens (pending agency review)
• Evaluation of SCRAM (Secure Continuous Remote Alcohol Monitoring device) (published April 2015)
• Evaluation of Washington State Target Zero Teams (published January 2015)
Other Alcohol-Impaired Driving Research
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Other Research
• Published Nov 2014• Important Note of
Caution• Now distributed with
requests for FARS drugged driving data