ABSTRACT

One of the earliest signals associated with the use of motor vehicles was introduced by the British parliament in the form of the 1865 Locomotives on Highways Act. This called for each self-propelled, steam-powered vehicle to have a crew of three: one driver, one stoker, and a man to walk 60 yards in front of the vehicle carrying a red flag to warn of its approach, the purpose being to avoid frightening the horses. Today, horse-drawn transport and steam-powered vehicles have almost vanished from the developed world, but signals have proliferated dramatically. Today, drivers are faced with a plethora of markings, signs, and signals designed to inform and regulate their behaviour, some fixed, some changeable, some unlit, some lit, but all needing to be seen by day and night. The form and location of markings, signs, and signals are strictly controlled so as to ensure consistency across road networks, although different countries have different rules (FHWA 2003; DfT 2005a). The factors considered in designing markings, signs, and signals are the distances from which they need to be visible; their shapes and colours, shape and colour being used as cues to meaning as well as being important for visibility; the advantages and disadvantages of pictograms rather than text in a specific language for signs; and the need for some means to attract attention to the sign or signal. The aspect of design that will be considered here is the use of light, either as an inherent part of the marking, sign, or signal or as a means to make the marking, sign, or signal conspicuous, visible, and legible at night.