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Appendix C | Technology as a key determinant of viability

Box C1

RFID tag types

Passive (read-only) tags have information stored on them during the

manufacturing process and can never be changed. They can be as small as

0.3 mm and can be read from a distance of about 6 metres. They do not require

batteries but are ‘woken up’ when they receive a query from the RFID reader.

The RFID tag responds by transmitting its unique ID code and other data back

to the reader. Semi-passive RFID tags contain a small battery that boosts the

range. WORM tags (write once read many) enable users to encode tags at the

first instance of use, after which the code be comes locked and cannot be

changed.

Active (read-write) tags include a battery, making them larger and more

expensive but permitting them to be read from 100 metres or more. a Information

on the tags can also be updated when the tag is within range of a reader. They

operate as transponders because they contain a transmitter that is always ‘on’.

a. Although the read range is often quoted as 30 metres. Those with an extended range are classified

as ‘enhanced’ RFID tags, such as those tags scheduled to be trialled by the UK Ministry of Defence

towards the end of 2006.

Source: Adapted from Collins (2004).

Dedicated Short Range Communication (DSRC)

Both DSRC and RFID involve a wireless technology based on tags and roadside

readers. The terms tend to be used synonymously, although RFID is regarded by

some as a subset of DSRC. There is also a view that DSRC is more suited than RFID

for road-user charging in that it can operate on a ‘peer-to-peer’ basis, compared

with the normal ‘master-slave’ relationship for RFID. Also, the transmission systems

differ: DSRC delivers a far greater data rate (25 Megabits per second) and range (one

kilometre) than RFID (250 kilobits and a 10 metre range) (RFID Journal undated).

Internationally, there appears to be strong interest in the use of DSRC for road

user charges. DSRC is widely employed for electronic tolling in Japan, based on its

‘expandability, high reliability, wide communication area, and efficient use of limited

frequency resources’ (Nakamura and Kodan 2003, p. 38).

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