Table 1.

Study Outcomes

Outcome type	Outcome descriptor	Level of impairment	Description
Subjective	Karolinska Sleepiness Scale	Low to Severe	Sleepiness in the prior 5 minutes ranging from Extremely Alert [1] to Very Sleepy, Fighting Sleep [9].
	Likelihood of Falling Asleep	Low to Severe	Likelihood of falling asleep in the next few minutes, ranging from Very Likely [1] to Very Unlikely [5]
	Sleepiness Symptoms Questionnaire	Low to Severe	Frequency of sleepiness symptom experienced in past 15 minutes, ranging across Not at all [1], Occasionally [3], Frequently [5], and Most of the Time [7].
	SSQ1: struggle to keep eyes open
	SSQ2: Vision Blurred
	SSQ3: Nodding Off to Sleep α
	SSQ4: Difficulty Keeping to Middle of Road
	SSQ5: Difficulty Maintaining Correct Speed
	SSQ6: Mind Wandering α
	SSQ7: Reactions are Slow α
	SSQ8: Head Dropping
Objective	Emergency Braking	Severe	In-Vehicle Safety Instructor Applies the Emergency (second) Brake as a Safety Intervention, representing Near-Crash Events.
	Lane Deviation	Moderate	Number of Times (per 15 minutes) that one or more Vehicle Wheels Crossed the Lane Markings
	Johns Drowsiness Scale ≥4.5	Severe	Composite JDS scores that equaled or exceeded 4.5
	Johns Drowsiness Scale ≥2.7	Moderate	Composite JDS scores that equaled or exceeded 2.7
	EEG Microsleep (Fall Asleep Event)	End-state	>3 s of EEG activity 8hz or less