Electronic Toll Collection (ETC) is an automatic tolling system applied to expressways, toll bridges and tunnels. Generally, the system collects the toll via wireless communication between in-vehicle transponders and roadside transceivers, and conducts settlement processing with banks via computer network. Vehicles therefore can pass through the tolling points directly without stopping to pay the toll.
Typical method for implementing electronic toll collection is tolling via wireless communication, while automatic number plate recognition (ANPR) is now starting to gain ground in some countries.
Tolling via wireless communication:
The system collects the toll via wireless communication between the roadside transceiver and in-vehicle transponder, which is the mainstream approach adopted in most of the countries. There are various types of wireless communication for tolling, ranging from dedicated short-range communication (DSRC), radio frequency identification (RFID), satellite positioning, etc.
Tolling via automatic number plate recognition:
The system can detect vehicles on the monitored road and automatically extract the number plate information, including Chinese characters, English letters, Arabic numerals and plate colors, for processing. It is widely applied for access control and parking management. At present, it is not yet mature to rely solely on ALPR technology to implement electronic toll collection. Successful cases are still rare, merely applied in South Africa, Sweden and a few other countries.
1. The recognition accuracy of ANPR technology is adversely affected by the defective number plate status (such as damaged or stained plate), unstandardized number plate format (such as customized patterns in Thai number plate), and unfavorable weather condition (such as rain and fog, and is sensitive to light). It results in a generally low recognition accuracy, requiring much human efforts to correct errors manually at the back-office system. Compared with automatic number plate recognition, wireless communication can improve identification precision to achieve higher success rate in auto-tolling, thereby reducing the operating cost of the entire system.
2. Tolling via wireless communication requires higher investment, especially the in-vehicle transponder cost, and need to consider the issue of how to get the transponder installed in vehicle. While when adopting ANPR technology for tolling, the total investment cost is lower, because there is no transponder cost but cost of upgrading roadside facilities.
Currently, automatic license plate recognition is rarely used for tolling purposes, but it is an indispensable means of monitoring and law enforcement in tolling system. Tolling via wireless communication is still the mainstream given the technology maturity and identification success rate.