National Highway Traffic Safety Administration NHTSA Research on Impaired Driving Heidi Coleman...

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


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


• 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


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


• 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


NRS - Team Sets Up


NRS - As Drivers Approach


NRS - First Thing Drivers See


NRS - Data Collection Underway


NRS - Data Collection (continued)


NRS - We’re Ready for Every Situation


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%


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+


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


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.


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%


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


Crash Risk Study

• Research Note published February 2015

• Full report in review• Hope to publish report in

2015


• 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


• 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


• 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


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)


Crash Risk Study


Study continues


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%)


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


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


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


• 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


• 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


• 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


Other Research

• Published Nov 2014• Important Note of

Caution• Now distributed with

requests for FARS drugged driving data


Thank you

[email protected]

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