The capacity of an object to stand out in relation to its background and thus be readily discovered by the eye. The ability to perceive or distinguish mentally, by understanding, not merely by the senses. Relatively recent innovation consisting of two additional strong lights placed on the lower front portion of a locomotive. The position of these lights creates a distinct triangular pattern that improves visibility for the railroad engineer and makes the locomotive much more apparent to drivers approaching a railroad crossing. A luminance less than about 0.034 candela per square meter.
Unit of measure is the candela per square meter.
Applies to multiple classes of roads and streets. The period approximately 60 minutes after sunset until 60 minutes before sunrise. Generally associated with adaptation to a luminance of at least 3.4 candelas per square meter. The interval between the beginning of a stimulus and the beginning of a response by an observer. An active traffic control device containing a red lens 8.5 inches in diameter that flashes when a train approaches a railway crossing.