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We know that alcohol negatively influences a driver's ability to drive. Governments typically combat this by making drunk driving illegal, and use the concentration of alcohol in breath or blood as the definitive measure as to whether a crime has been committed or not.

In this sense - alcohol in the blood/breath is merely a proxy for impairment, but one that is quite reliable - when one is drunk they're going to show alcohol in the blood stream, this is able to be accurately measured.

There are other ways a driver can be impaired as well - quite commonly through sleepiness/fatigue, but also other drugs, or distraction (driving while texting), or emotional distress.

The prospect of 'drugged driving' comes up quite commonly in discussions about legalising cannabis. Where there is a reliable test of alcohol impairment - it's not quite the same for cannabis and other drugs - the problem being that saliva tests can show the presence of the drug long after the person has sobered up. A blood test might be viable - but that's perhaps not practical, in terms of getting a cop to administer to a driver.

With fatigue, it's even more problematic - there's no drug to detect at all.

In light of this - has any general impairment test - that perhaps tests reaction times or some other metric, that can be administered at a roadside, been developed?

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  • $\begingroup$ If by test you mean something short of simulated driving, the answer is probably no, otherwise simulated driving would not be used in studies anymore. See e.g. doi.org/10.1053/rmed.2001.1109 The problem with a really good test like that (beside impracticality for detecting intoxication, because it might subside by the time the elaborate &long test is administered/done) is that it would also [partly] flag some medical conditions like obstructive sleep apnea. Of course, there are plenty of medical conditions that disqualify one for a driving license; bad eyesight for example. $\endgroup$ – Fizz Oct 5 '18 at 3:13
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Based in Madison, Wisconsin, CTC & Associates provides technical communications services for the transportation sector, and together with the Minnesota Department of Transportation (MnDOT), they put together a report on how to monitor driver fatigue:

to serve as a synthesis of pertinent completed research to be used for further study and evaluation by MnDOT. This [Transport Research Synthesis (TRS)] does not represent the conclusions of either CTC & Associates or MnDOT. (MnDOT, 2015)

The following (apart from ESS - see below) are some of the studies presented in the MnDOT report.

In-vehicle Technologies

Balkin, et al. (2011) talks about technologies which can detect or predict driver fatigue.

Technologies that objectively detect or predict operator fatigue may be used to effectively complement or even supplant organizational or regulatory approaches. Over the past decade and a half, there have been considerable advances in relevant technologies, including onboard devices that monitor drivers’ state or level of performance as well as devices that predict fatigue in advance of a work cycle or trip.

Barr, Popkin and Howarth (2009) also reviews and discusses unobtrusive, in-vehicle, real-time drowsy driver detection and fatigue monitoring/alerting systems.

The study focuses on recent developments in two areas:

  • Mathematical models that predict operator alertness and performance at different times. Factors involved in the assessment include the amount of sleep obtained or missed, circadian factors (the 24- hour cycle of physical, mental and behavioral changes) and workload.
  • Vehicle-based monitoring technologies that assess behavioral characteristics of the driver such as eye gaze, eye closure, head position and movement, and heart rate.

Roadside and other Out-of-vehicle technologies

Fitness for Duty

There is the Karolinska Sleepiness Scale [KSS] (Åkerstedt & Gillberg, 1990; Kaida, et al., 2006) and there is the Epworth Sleepiness Scale [ESS] (Johns, 1991). Both are self-report scales, frequently used in studies measuring subjective sleepiness, that measure the individual’s drowsiness. The KSS is a 9-point verbally anchored scale going from ‘extremely alert’ to ‘extremely sleepy–fighting sleep’, whereas the ESS uses a 4-point scale from never doze to high chance of dozing.

The Epworth Sleepiness Scale (ESS) (named after The Epworth Sleep centre in Melbourne, Australia) is used by doctors here in the UK to point toward the possibility of sleep disorders such as Sleep Apnoea. You can see an example PDF of the questionnaire at the Warrington and Halton NHS Hospitals website. It is a self-evaluation questionnaire devised to determine general sleepiness observed by the individual based on usual chances of dozing off or falling asleep while engaged in eight different activities.

Not wishing to add any validity to the system, I thought I would mention that Optalert talks about a testing system they developed themselves and are promoting, called the Johns Drowsiness Scale (JDS). It was developed by Optalert’s Founding Director, and developer of ESS, Dr Murray Johns, and comparing it to ESS, and Blood Alcohol Concentration Readings, they say that

With 30 Per Cent Of Road Fatalities Attributed To Drowsy Driving, At Optalert We Believe The Johns Drowsiness Scale (JDS™) Will, In The Near Future, Become As Important As Blood Alcohol Concentration (BAC) Readings. (Source: JDS vs BAC - Optalert)

Whilst assessing the use of a simple balance task for assessing fitness for duty, Sargent et al. (2012) states:

results indicate that postural balance may be a viable tool for assessing fatigue associated with time of day, but may not be useful for assessing fatigue associated with extended hours of wake.

Roadside Testing

A pilot study was conducted (Forsman, et al., 2014) and it states that the method put together for the pilot...

further developed, may provide a drowsiness test for roadside surveillance.

Further Reading

MnDOT. (2015) Monitoring Motor Vehicle Driver Fatigue
Retrievable form http://dotapp7.dot.state.mn.us/projectPages/pages/projectDetails.jsf?id=35917&type=DOCUMENT

Plus Chapters 9 & 10 of:

National Academies of Sciences, Engineering and Medicine. (2016). Commercial Motor Vehicle Driver Fatigue, Long-Term Health, and Highway Safety. Washington (DC): National Academies Press
DOI: 10.17226/21921 NBK: 384966 [Free PDF]

References

Åkerstedt, T., & Gillberg, M. (1990). Subjective and objective sleepiness in the active individual. International Journal of Neuroscience, 52(1-2), 29-37.
DOI: 10.3109/00207459008994241 PMID: 2265922

Balkin, T. J., Horrey, W. J., Graeber, R. C., Czeisler, C. A., & Dinges, D. F. (2011). The challenges and opportunities of technological approaches to fatigue management. Accident Analysis & Prevention, 43(2), 565-572.
DOI: 10.1016/j.aap.2009.12.006

Barr, L., Popkin, S., & Howarth, H. (2009). An evaluation of emerging driver fatigue detection measures and technologies (No. FMCSA-RRR-09-005). United States: Federal Motor Carrier Safety Administration.
Retreivable at https://rosap.ntl.bts.gov/view/dot/34394

Johns, M. W. (1991). A New Method for Measuring Daytime Sleepiness: The Epworth Sleepiness Scale. Sleep, 14(6), 540-545.
DOI: 10.1093/sleep/14.6.540

Forsman, P., Pyykkö, I., Toppila, E., & Hæggström, E. (2014). Feasibility of force platform based roadside drowsiness screening–A pilot study. Accident Analysis & Prevention, 62, 186-190.
DOI: 10.1016/j.aap.2013.09.015

Kaida, K., Takahashi, M., Åkerstedt, T., Nakata, A., Otsuka, Y., Haratani, T., & Fukasawa, K. (2006). Validation of the Karolinska sleepiness scale against performance and EEG variables. Clinical Neurophysiology, 117(7), 1574-1581.
DOI: 10.1016/j.clinph.2006.03.011

MnDOT. (2015) Monitoring Motor Vehicle Driver Fatigue
Retrievable form http://dotapp7.dot.state.mn.us/projectPages/pages/projectDetails.jsf?id=35917&type=DOCUMENT
TRSs are also searchable at http://dotapp7.dot.state.mn.us/projectPages/pages/homepage.jsf

Sargent, C., Darwent, D., Ferguson, S. A., & Roach, G. D. (2012). Can a simple balance task be used to assess fitness for duty?. Accident Analysis & Prevention, 45, 74-79.
DOI: 10.1016/j.aap.2011.09.030

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In light of this - has any general impairment test - that perhaps tests reaction times or some other metric, that can be administered at a roadside, been developed?

Yes. I believe it is called the Standardised Field Sobriety Test (SFST).

No, I'm quite serious -- read over your question, and consider whether a well-administered field sobriety test has utility as a "general impairment test" in things other than alcohol intoxication.

It involves the administration of a short battery of attentional, cognitive and behavioural tasks, whose results possess a degree of sensitivity and specificity in a number of risk factors for motor vehicle accidents.

The following reference identifies some parts of the SFST that are sensitive to sleep deprivation:

Sleep Deprivation Does Not Mimic Alcohol Intoxication on Field Sobriety Testing

Abstract:  Previous research shows that sleep deprivation (SD) produces cognitive impairment similar to that caused by alcohol intoxication. Individual studies suggest that SD also causes deficits in motor skills that could be mistaken for intoxication. Consequently, SD often is used as a defense when an impaired driver is charged with driving while intoxicated. Twenty-nine adult subjects participated in two test sessions each, one after a full night’s rest and the other after wakefulness of at least 24 h. Subjects consumed prescribed amounts of alcohol during each session. Law enforcement officers conducted field sobriety tests identical to those with which a driver would be assessed at roadside. Researchers also measured clinical responses of visual function and vital signs. The presence and number of validated impairment clues increase with increasing blood alcohol concentration but not with SD. Thus, SD does not affect motor skills in a manner that would lead an officer to conclude that the suspect is intoxicated, unless intoxication also is present.

Being well-rested, for example, will increase your pupil size substantially.

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Governments typically combat this by making drunk driving illegal, and use the concentration of alcohol in breath or alcohol as the definitive measure as to whether a crime has been committed or not.

Huh? The crime is the BAC itself. However, I get what you're saying. BAC predicts something that is reliably associated with car accidents, so BAC itself is used as a proxy even if that "something" e.g. poor coordination is absent entirely.

With fatigue, it's even more problematic - there's no drug to detect at all.

The overarching premise here, however, is that the only "weapon" to prevent fatigue-based accidents is through the use of a police-man's truncheon.

Also, are you concerned with fatigue, or hours since last having slept? Realistically, it is not possible to detect fatigue in the way that you are thinking. You could detect someone who "most certainly has not slept in the past 100 hours" but fatigue alone is a far more nuanced matter.

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  • $\begingroup$ I have yet to read the full article but reading that abstract, it said "Thus, SD does not affect motor skills in a manner that would lead an officer to conclude that the suspect is intoxicated, unless intoxication also is present." which to me argues against the use of SFST for detecting fatigue $\endgroup$ – Chris Rogers Mar 11 '18 at 10:04
  • $\begingroup$ yes -- the study basically states that sleep deprivation produces a pattern of results that won't lead you to think that they're drunk, when in fact, they're just tired. however, if global impairment (by any means) is your endpoint of interest, then this is a minor point. $\endgroup$ – faustus Mar 11 '18 at 10:11

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