Two years after an original review of display technologies for variable message signs (VMSs), the authors of this article reconsider the new technologies for collective driver information, and argue that improved light-emitting diodes (LEDs) could become the dominant and cost-effective light source. The following VMS technologies are compared: (1) rotating planks and prisms; (2) roller blinds; (3) electromagnetic reflecting flip disk; (4) lamp matrices; (5) fibre optics; (6) LEDs; and (7) liquid crystal displays (LCD). Fibre optic signs and LEDs perform best. Fibre optic displays have excellent visibility in all weather conditions, although they can be difficult to read in direct sunlight. The fibre optic reflective disk combines the qualities of fibre optics and the reflective disk to be exceptionally visible in direct sunlight. The advantages and disadvantages of first-generation technology are listed. R-R Industrial Controls has developed a new generation of LEDs for transport and traffic applications. Its high intensity yellow LED, Rigel, has greatly increased optical efficiency and reduced power consumption. Its technology has been chosen for several British VMS projects.
Abstract