Vehicle intelligent tag/transponder
There are a variety of different vehicle intelligent tag/transponder types available to transport operators, but these all generally fall under the category of Radio Frequency Identification (RFID) tags which are very similar technology to smartcards. This technology is primarily used for access control and to provide real-time vehicle location information. The system consists of hardware components in the form of the RFID tags themselves, roadside RFID readers/transmitters and a central computer systems, as well as software in the form of applications to interpret the RFID information.
In this system RFID tags can be encoded with vehicle and/or driver information which is read by an RFID reader unit using radio waves, potentially from several metres away. The RFID reader unit is generally located at the roadside, for example at a bus stop, or at an access point, such as a restricted access road with an electronic gate or retracting bollards. The reader unit continuously emits a radio signal of a specific frequency, and when a recognised RFID tag comes into range the encoded information on the tag is transmitted via the radio signal to the reader in an encrypted format. The reader decodes this information using an embedded processing unit. In access control applications, the reader may hold information relating to allowed vehicles and provide access based on this.
In other systems, where RFID technology is used to provide vehicle location information, the roadside reader unit also includes an embedded wireless radio transmission device, typically a GPRS device, to transmit vehicle information, stop number and a time and date stamp to a central location such as a control centre. This type of system may also operate in an alternative way with the RFID tag located at the stop and the reader unit located on-board the vehicle. Whichever way the system is implemented, once the data is received at the control centre it is interpreted using a software application on the central computer system. This software can match the stop number to a predefined GPS stop location to determine real-time vehicle location information. This data can be used to provide real-time passenger information (RTPI) using estimated time of arrival information based on route distance and average vehicle speed. However, because this system does not continuously track vehicles, accurate speed information is not available and congestion cannot be detected, and this may result in RTPI inaccuracies.
Similarly to smartcard technology, RFID tags do not generally have an in-built source of power. The energy required to perform transactions with the RFID reader unit is derived from the radio frequency field emitted by the reader. The card has an embedded wire loop which induces a current from this field when it is in range of the reader, and this supplies energy to the card so that communication can occur. RFID tags can also be provided in the form of cards which require contact with the reader unit to provide information, generally via a card slot. This method is not practical for vehicle location purposes, but may be used for access control. In contact systems the card also has no internal power source, and energy is derived via direct connection with the conductive pad on the surface of the card.
- Automatic vehicle location
- Traveller information
- Traffic management in terms of access control
Benefits and cautions
RFID systems can provide a relatively simple form of real-time vehicle location however the infrastructural requirement can mean that they are not cost effective. This fact added to the inability to provide continuous vehicle tracking means that this technology is likely to be outperformed by other automatic vehicle location systems such as GPS. The technology can however be a valuable supplementary system to GPS, providing location information when there are signal disruptions. In this sort of role an RFID system can be a cost effective back-up, particularly if the infrastructural cost is minimised by placing RFID tags at stops and locating reader units on vehicles. In this way the reader unit can be integrated with the on-board computer system to utilise existing in-vehicle radio equipment for data transfer purposes, and this further reduces potential hardware costs.