This chapter has shown that ANPR is a viable and valuable technology both as a primary means of charging, and as a tool to aid enforcement and compliance. It is also clear however that ANPR has, and will always have, some limitations in usability and performance, and these need to be taken into account when incorporating ANPR into a road charging system implementation. While performance limitations may to some extent be mitigated by advancements in technology and processing algorithms, other limitations around the nature of registration plates need legal measures.

Chapter Contents:

• 11.1 Introduction to ANPR
• 11.1.1 Short history of ANPR
• 11.1.2 How ANPR works – a short technical description
• 11.1.2.1 Triggering
• 11.1.2.2 Segmentation
• 11.1.2.3 Classification
• 11.1.2.4 Post-processing
• 11.1.2.5 Logging of results
• 11.1.3 ANPR cameras
• 11.1.3.1 CCTV cameras
• 11.1.3.2 Pulsed IR cameras
• 11.1.3.3 Digital cameras
• 11.1.4 Effect of plate design on ANPR
• 11.1.4.1 Plate formats and fonts
• 11.1.4.2 Reading international plates
• 11.1.5 Expected performance of ANPR systems
• 11.1.5.1 Plate condition
• 11.1.5.2 Camera geometry
• 11.1.5.3 Moving vehicles
• 11.1.5.4 Malicious manipulation
• 11.2 The use of ANPR in road pricing
• 11.2.1 Primary charging using ANPR
• 11.2.1.1 Stockholm congestion charge
• 11.2.1.2 Ontario Highway 407 Express Toll Route (ETR)
• 11.2.1.3 ANPR used for compliance and enforcement
• 11.2.1.4 Central London congestion charge
• 11.2.1.5 German lorry road user charge system
• 11.3 Implementation of ANPR
• 11.3.1 General points
• 11.3.2 Case study: London congestion charge zone
• 11.4 Standards relevant to the implementation of ANPR
• 11.4.1 Interface standards
• 11.4.2 Performance and deployment standards
• 11.5 Summary and conclusions
• References

Inspec keywords: traffic engineering computing; character recognition; road traffic; text detection; road pricing (tolls)

Other keywords: road charging system; registration plates; ANPR technology; automatic number-plate recognition

Subjects: Image recognition; Computer vision and image processing techniques; Traffic engineering computing