Abstract
Users of transport systems at night depend on a variety of visual clues to guide them. These clues are significant when they become conspicuous, that is, when they attract the attention of the user. In transport systems two general types of clues for nighttime use are commonly found. One type is self luminous, called primary, such as signal lights, rear vehicle lights, barricade lights, etc. The other type reflects light from it's surface and is called secondary. Both types depend on contrast with the background in order to be conspicuous. This paper reviews the devices used to obtain conspicuity in modern transport systems.