4.3 Vision, Hearing, Fatigue, Emotion & Substance Effects

The Driver Is Part of the Safety System

OL 235 requires study of physical and mental capabilities, including vision, hearing, fatigue, illness, emotion, alcohol, and drugs. These factors affect what a driver detects, how accurately a situation is interpreted, and whether a correct response can be executed. An instructor evaluates function, not a diagnosis.

Vision and Perception

Central vision reads detail while peripheral vision detects movement and supports lane position. Darkness, glare, speed, dirty glass, fatigue, and some health conditions can narrow the useful visual field or reduce contrast. Corrective-lens restrictions on a license must be followed. Teach students to move their eyes, turn the head when needed, and position the vehicle to improve sightlines rather than relying on a claimed universal number of visual degrees.

Depth and speed judgments improve with multiple cues: relative motion, size change, lane markings, shadows, and the rate at which a gap closes. A motorcycle can look farther away or slower because of its small frontal image. At night, one visible headlamp may be a motorcycle rather than a car with a failed lamp; delay the turn until the path is confirmed.

Hearing and Communication

Hearing can alert a driver to sirens, horns, tire noise, or mechanical problems, but safe driving cannot depend on hearing alone. Scan mirrors for emergency lights and watch other traffic's reactions. A hearing-impaired student can use visual strategies and properly fitted adaptive devices. The instructor should agree on clear visual or tactile emergency cues before the lesson without creating a new distraction.

Fatigue, Illness, and Emotion

Fatigue slows recognition, encourages fixation, and may produce lane drift or brief sleep. Warning signs include repeated yawning, missed signs, wandering thoughts, heavy eyelids, and difficulty remembering the last miles. Coffee, cold air, and loud music do not restore adequate alertness. The reliable response is to stop at a safe place and rest or change to an alert driver.

Strong anger, anxiety, grief, or excitement can narrow attention and increase impulsive decisions. Use a brief self-check before driving: Can the person focus, follow directions, and accept correction? If not, postpone the lesson. During training, use calm directions and create a safe pause after an error. Do not argue while the vehicle is moving.

Illness, pain, and low blood sugar can also impair performance. An instructor is not expected to diagnose; observe the student's condition and avoid on-road instruction when safe control is doubtful. Call emergency services for urgent medical signs rather than attempting to drive the person to care while supervising a learner.

Alcohol, Cannabis, and Medication

Alcohol commonly degrades judgment before the user recognizes it. Cannabis and other drugs may affect attention, coordination, perception, or time judgment. Prescription and over-the-counter medicine can cause drowsiness or other effects. Read warnings and obtain qualified medical or pharmacist advice. Mixing substances can magnify or make impairment unpredictable.

The exam may ask what an instructor should do when a condition is observed. Safety takes priority over completing the appointment. Document the objective reason under school policy without making unsupported medical claims.

Objective Observation

Document behavior that affects instruction: repeated missed signals, difficulty staying awake, inconsistent pedal control, or inability to follow a simple direction. Avoid diagnosing a medical condition or recording insulting conclusions. Ask whether the student can continue safely, move to a safe place, and involve the school's emergency or guardian process as appropriate. A student who self-reports a new vision, medication, or health issue should be directed to qualified guidance and DMV requirements; the instructor does not waive a restriction based on a short road demonstration.

Plan accommodations before the engine starts. Examples include an agreed visual cue, additional time for a parked explanation, glare management, or permitted adaptive equipment. An accommodation changes access to instruction, not the requirement to control the vehicle safely. Reassess its effectiveness and seek formal direction when license restrictions may need review.