Taxonomy and descriptionTerminology
P arking Guidance and Information (PGI) systems use variable message signs (VMS) to provide drivers with information on the location and the availability of spaces in car parks. They have been in use since the 1970s, initially implemented in Aachen ( Germany ). Over subsequent years, their use has increased and it has been estimated that over 50 systems of this type are in operation worldwide (Polak et al., 1990; Axhausen et al., 1994; Tsopelas, 2000; Thompson and Bonsall 1997).
Earlier systems, such as that in St Helier (Gercans, 1984), involve limited function signs with very simple space counters and availability display units. However the technology used for the systems evolved dramatically. Nowadays, electronic message signs are able to display a full range of messages and symbols. On an operational level, recent PGI systems consist of the following elements and equipment (Polak et al., 1990; DfT, 2003)
driver information equipment which may be of various types, with the most usual being the variable message signs (VMS) panel located at roadside;
occupancy loops or automatic vehicle identification (AVI) equipment that can count the number of vehicles entering and exiting the car parks, and closed circuit television (CCTV) equipment ;
television cameras monitoring traffic status in the streets;
electronic payment devices using electronic, inductive, magnetic or smart card technology;
electronic parking meters used to control how long vehicles park in the streets, charging fees and checking availability;
a control centre with an occupancy rate equalizer (equilibrium) that controls the display of information on the VMS;
a telecommunication network and computers to exchange data (information) between the above systems.
A review of a typical PGI system structure can be found in Polak et al. (1990) and DfT (2003) and Spencer (2001) . A typical PGI system consists of the following stages. M onitoring equipment at the parking areas establish the flow into and out of the car parks in order to calculate the number of available spaces. Car park count data are transmitted back to a central location and processed before being presented to the public via VMS or other media such as radio or a web site. VMS displays are located at suitable decision points on the network, so that a driver’s journey time to a vacant space is minimised.
Nowadays, advanced PGI systems can present a range of real time information, including waiting times and prices. These systems can also be developed jointly with other aspects related to traffic management that provide users with real-time information on road accidents, traffic congestion, traffic flow restraints and the location of parking facilities (Viena, 2003)
See Also: Variable Message Signs
In-Vehicle Route guidance