Visibility & Lighting Conditions Flashcards
7 cards from real ACTAR practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Visibility & Lighting Conditions flashcards as text
Under FHWA minimum retroreflectivity guidelines, what is the minimum retroreflectivity level for white pavement markings?
Answer: 100 mcd/m²/lux
The FHWA minimum retroreflectivity standard for white pavement markings is 100 mcd/m²/lux, below which markings may be inadequate for safe nighttime travel.
In a nighttime pedestrian collision reconstruction, 'recognition distance' differs from 'detection distance' in that:
Answer: Detection distance is where the object first becomes visible; recognition distance is where the driver can identify what the object is
Detection distance is where the driver can first see an object, while recognition distance is the closer distance at which the driver can identify it as a specific hazard, allowing for appropriate response.
Koschmieder's law is applied in accident reconstruction to:
Answer: Determine the visibility distance in foggy, smoky, or hazy atmospheric conditions
Koschmieder's law defines the relationship between the atmospheric extinction coefficient and the maximum visibility distance in conditions such as fog, smoke, or heavy rain.
A reconstructionist analyzing 'adverse lighting conditions' would consider which of the following as a significant factor in driver visual performance?
Answer: The dark adaptation state of the driver's eyes when transitioning from bright to dark environments
Dark adaptation—the process by which the eyes adjust to reduced illumination—significantly affects driver visual performance; a driver transitioning from bright to dark conditions may have reduced nighttime vision for several minutes.
What effect does a wet road surface have on the retroreflectivity of pavement markings at night?
Answer: It decreases retroreflectivity because a water film prevents light from reaching retroreflective beads
A wet road surface covers the retroreflective glass beads embedded in pavement markings with a water film, significantly reducing or eliminating retroreflectivity and making markings much harder to see at night.
In nighttime accident reconstruction, an illuminance meter (light meter) is used to measure:
Answer: Ambient light levels at the accident scene in foot-candles or lux
Illuminance meters measure ambient light levels at the accident scene in foot-candles (English) or lux (SI), providing objective data about the lighting conditions that existed at the time of the collision.
The 'nighttime viewing distance' for a stationary object in a roadway depends LEAST on which of the following?
Answer: The ambient air temperature at the accident scene
Ambient temperature has minimal direct effect on nighttime viewing distance; the primary factors are headlight output, object reflectivity/conspicuity, and luminance contrast between the object and background.