ACTAR Human Factors 3 — Questions and Answers
Question 1: What is the primary reason nighttime pedestrian detection distances are shorter than daytime distances even with functioning headlights?
- Drivers are more fatigued at night
- Pedestrian clothing reflectivity is lower and headlight illumination is limited (Correct answer)
- Headlights cause temporary blindness
- Traffic is lighter so drivers drive faster
Correct answer: Pedestrian clothing reflectivity is lower and headlight illumination is limited
Headlights illuminate a limited range and pedestrians in dark clothing may only reflect enough light for detection within 60–100 feet, far less than daytime visibility.
Question 2: The 'last clear chance' doctrine in accident reconstruction relates to which human factors concept?
- Time-distance analysis of evasive opportunity (Correct answer)
- Driver fatigue at the time of impact
- Seatbelt use and injury causation
- Speed estimation from skid marks
Correct answer: Time-distance analysis of evasive opportunity
Last clear chance analysis uses time-distance calculations to determine whether either party had a perceivable, reachable opportunity to avoid the collision.
Question 3: Which term describes the minimum time a driver needs to process a signal before being able to initiate a voluntary response?
- Detection latency
- Discrimination time
- Irreducible minimum reaction time (Correct answer)
- Cognitive processing gap
Correct answer: Irreducible minimum reaction time
The irreducible minimum reaction time (roughly 0.5 s) represents the physiological floor below which a voluntary response cannot occur regardless of expectancy.
Question 4: Speed estimation errors by drivers tend to be greatest under which of the following conditions?
- Driving on a wide, open highway at constant speed
- Transitioning from high-speed to low-speed environments (Correct answer)
- Following a vehicle at a steady gap
- Driving during daylight on familiar roads
Correct answer: Transitioning from high-speed to low-speed environments
After sustained high-speed driving, the perceptual system adapts, causing drivers to underestimate speed in lower-speed zones—a well-documented adaptation effect.
Question 5: Which glare type is most likely to temporarily impair a driver's vision at night when an oncoming vehicle's headlights are misaligned?
- Disability glare (Correct answer)
- Discomfort glare
- Transient adaptation glare
- Veiling luminance glare
Correct answer: Disability glare
Disability glare occurs when stray light within the eye reduces contrast of the retinal image, directly impairing vision rather than merely causing discomfort.
Question 6: How does driver expectancy influence crash causation in intersection accidents?
- High expectancy always improves safety by preparing the driver
- Violated expectancy can delay recognition and reaction to unexpected events (Correct answer)
- Low expectancy speeds up response to unusual stimuli
- Driver expectancy has no recognized role in intersection crashes
Correct answer: Violated expectancy can delay recognition and reaction to unexpected events
When events violate a driver's expectancy (e.g., a wrong-way vehicle), perception and recognition are delayed because the brain must first resolve the discrepancy.
Question 7: What does the term 'conspicuity' mean in traffic accident human factors analysis?
- The legal conspicuousness of a posted sign
- The probability that an object will attract a driver's attention in the environment (Correct answer)
- The brightness of vehicle headlights
- The legibility of road markings at night
Correct answer: The probability that an object will attract a driver's attention in the environment
Conspicuity refers to the degree to which an object is able to attract attention based on its sensory properties relative to the background.
ACTAR Human Factors 3
What is the primary reason nighttime pedestrian detection distances are shorter than daytime distances even with functioning headlights?