An important problem of Intelligent Transport Systems (ITSs) is how technically sophisticated they should be. Nearly all ITSs use at least one of the following media: twisted copper pair, coaxial cable, and optical fibre. These media have different information channel capacities and transmission speeds. Twisted copper pair has limitations in transmitting high data rates. Coaxial cable can transmit multiple video channel, but requires frequent amplification along the cable. Single-mode optical fibre has extremely high information capacity and high reliability and freedom from interference. It is easy to maintain and install. It is thus the superior communications medium for most ITS systems, and will be used more and more as demands on ITS performance rise. Well over 90% of fibre sold for ITSs is single-mode. In advanced traffic management systems (ATMS), infrastructure size often determines which communications architecture to use. Large urban areas, with over 200 junction controllers, have used SONET ring technologies, based on optical fibres. For smaller areas with 50 to 200 controllers, the RS232 self-healing ring optical communications technology is excellent. Optical fibre is well suited to handling the increased data rates and capacities that present and future ITSs will require.
Abstract