Transcript Document

RITA: Measuring
impairment due to
alcohol and other
drugs at the roadside
Brian Tiplady
26th October 2006
RITA: Measuring
impairment due to
alcohol and other
drugs at the roadside
Brian Tiplady
26th October 2006
Alcohol and
Driving
• Large, effects
on accident risk
• Moderate
amounts of
alcohol lead to
substantial
increase in risk
Crash Risk with Alcohol
150
125
100
Relative
Risk
75
50
25
0
0
50
100 150 200 250
BAC mg/100 ml
Source: Compton et al., 2002
Alcohol Impairments
• Lab tests show impairment
on a wide variety of abilities
–
–
–
–
Attention
Motor skills
Memory
Comprehension and Judgement
• Both speed and accuracy of performance
are important
Other Drugs and Driving
• Performance effects easy to demonstrate in
laboratory at relevant doses
• Much harder to demonstrate increased driving risk
• New methods such as responsibility analysis have
increased reliability
• Now accepted that both prescription and illicit
drugs impair driving
– Benzodiazepines (when taken during the day, e.g. for
anxiety)
– Cannabis
The Enforcement Problem
• An offence to be in charge of a motorised vehicle
while unfit to drive through drink or drugs
• Alcohol is easy to measure in the body, and de
facto limits can be set up based on lab evidence
• Other drugs present different problems
– Non-invasive assays generally not adequate
– Many drugs and more metabolites
– Illicit drugs are much harder to study
• Drugs other than alcohol, particularly illicit ones,
are a growing problem
The Enforcement Problem
In practice, for drugs other than alcohol:
• Only presence or absence of drug can be
determined with sufficient reliability
• Impairment must be demonstrated in the
individual case, and cannot be inferred from
drug concentrations
• Present method is Field Impairment Testing
Field Impairment Testing (FIT)
• Administered by trained Police Officers
– Pupil examination
– Estimate 30 seconds
– Walk heel to toe along
a straight line and turn
– One leg stand
– Finger to nose with eyes shut
• Effective, but has considerable subjective element
• Could we do better with objective tests similar to
those used in the lab?
Home Office Scientific Branch
(HOSDB) Project
• Development of a portable roadside screening
device for driver impairment
• Battery of tests assessing different aspects of
driving ability
• Tests should be straightforward, consistent, and
easy to use by all drivers
• Short duration (~10 minutes)
• Sensitive to effects of a wide range of legal and
illicit drugs
Home Office Scientific Branch
(HOSDB) Project
• Phase I : Development and evaluation of several
prototype systems
• Phase II : Development of single portable tester at
HOSDB, with range of candidate tests
• Phase III : Evaluation of tester:
– Substantial numbers of subjects
– Wide age-range
– Variety of drugs (alcohol, prescribed, illicit)
Main target is drugs other than alcohol. Alcohol is useful
for evaluation because of its well-documented effects
Phase I: Layout of one tester
Phase I: Layout of one tester
Tests in one Phase I System
• Arrow Flankers
– Attention in the presence of distracting information
• Paired Associate Learning
– Spatial working memory
• Length Estimation
– Size judgements
Arrow Flanker Test
Arrow Flanker Test
Arrow Flanker Test
Evaluations of Prototype Tester
1. Volunteer Study with Alcohol
– 15 healthy volunteers (8 male, aged 1835) took part
– Low (50 mg/100 ml) and high (80)
alcohol showed significant impairment
compared to placebo
– Impairment to both speed and accuracy
Evaluations of Prototype Tester
2. Field Study at Music Festivals
– 55 volunteers recruited (30 male, aged
17-45) took part
– Drug and alcohol consumption from
questionnaire
– Cozart® saliva test and breathalyser
– Performance on impairment tester
Overall Impairment Index
ANOVA
High
Alcohol
Ethanol
F = 7.36
p<0.01
Drug
F = 0.55 n.s.
Low
Alcohol
Zero
Alcohol
Interaction F = 0.17 n.s.
-2
0
2
4
Impairment Index
6
Overall Impairment Index
Pairwise Comparisons
High
Alcohol
High vs Zero
Low
Alcohol
t = 3.58
p<0.001
Zero
Alcohol
Low vs Zero
t = 0.13 n.s.
-2
0
2
4
Impairment Index
6
Arrows Speed Accuracy
15
Red Circles:
High Alcohol
10
N of
Errors
Open Circles:
No and Low
Alcohol
5
0
300
400
500
Response Time (msec)
600
Conclusions
• Prototype devices effective both in lab and
field settings
• Impairments to speed and accuracy of
performance were detected
• Overlap between impaired and nonimpaired persons may be an issue
• Concept warrants further development
Phase II: Roadside Impairment
Testing Apparatus (RITA)
• Selection of tests from prototypes (30 mins)
–
–
–
–
–
–
Critical Tracking Task
Length Estimation
Paired Associate Learning
Sustained Attention to Response Test
Choice Reaction Time
Arrow Flanker Task
• Implementation on Handheld Device at HOSDB
– 14 cm diagonal screen size
– Input via touch screen and push buttons
Phase III
• Large scale evaluations
– N of subjects in the 00s
– Wide range of ages
• Alcohol evaluation study
– Recruitment complete
• Study/studies on other drug classes
• Test selection for final ten minute battery
Phase III Alcohol Evaluation
• Carried out at Royal Infirmary, Edinburgh
• 120 volunteers spread evenly across age-bands
18-24, 25-30, 31-40, 41-50, 51-60, 61-70
• Three sessions: one dose-finding and two main
• Dose of alcohol to take them to a maximum blood
alcohol concentration of 90 mg/100ml
– Sufficiently well-tolerated
– Most people unfit to drive at this concentration
• RITA and FIT carried out over next 2 hours
• Taxi home at end of session
Phase III Key Dates 2005/6
• 22nd November: Phase III presented to
Government’s Science and Technology
Committee
• 1st December: Protocol submitted to ethics
committee
• 4th December: Article in New Scientist
• 25th January: Recruitment started
• 4th April: Article on study in local paper
• 7th September: Sessions completed
• Ongoing: Data review and analysis
Recruitment
• Initially by newspaper advertisement
• Posters in waiting rooms, places of work
• Flyers distributed – carryouts were
particularly effective
• Word of mouth became increasingly
important as study went on
Recruitment
Summary and Conclusions
• Once sensitivity to alcohol is established,
work with other drugs may be initiated
• Opportunity both to improve enforcement
and to obtain more detailed knowledge of
drug effects on driving skills
• Persuasion is as important as enforcement
Brian Tiplady: Contact Information
Thanks to:
T: 0131 447 2171
M: 07760 263 283
E: [email protected]
W: www.penscreen.com
University of Surrey:
Andria Degia
Julia Boyle
HOSDB:
Philip Dixon
University of Edinburgh
Gordon Drummond
Stephanie Dodds
Caroline Maciver
Clinical Research Facility,
Edinburgh
Jean Antonelli
Sharon Cameron
Finny Paterson
Brian Tiplady: Contact Information