Exclusive interview: Paul Cowperthwaite on the technology behind London’s Congestion Charge success

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A new academic study by economists at the University of Lancaster has found that the number of road accidents the UK capital have dropped by 40% since London started its congestion charging scheme in 2003. Traffic Technology Today recently caught up with Paul Cowperthwaite, the general manager of road-user charging at TfL, to ask about the role of ALPR in the innovative system.

London was one of the first cities to use ALPR on such a large scale – why was this approach chosen?

When Congestion Charging was launched, Transport for London (TfL) needed a robust solution to address the issues within the capital. The zone is a relatively small area of just 8.1 square miles – having an area-based scheme was the best approach. The use of ALPR technology was the best solution for the scheme it supports both the charging mechanisms as well as the enforcement process.

How many cameras were installed initially and how many have been added over time?

We have actually reduced the number of cameras from 688 to 646 due to factors such as changes in road layouts meaning cameras become obsolete or through realigning cameras to improve performance.

How accurate/reliable do you find the ALPR system?

The London ALPR camera system is very reliable with 97% of all vehicles driving within the zone being captured on a daily basis. This percentage increases if vehicles pass more than one camera site. The accuracy of the ALPR interpretation is approximately 86% i.e. only 14 out of every 100 vehicles captured are ‘mis-read’ with the most common errors being the character ‘S’ being interpreted as a ‘5’. However, these errors are captured and rectified through manual checking.

Would you recommend this approach to other cities looking to implement a congestion charge?

Yes. The scheme has proved very successful with a sustained reduction in traffic. We have also been able to deliver customer improvements. We are, however, mindful of changes in technology so it is important that we keep reviewing the effectiveness of our solutions.

Is there anything about the system you’d like to improve?

We will be making improvements to our system and cameras over the coming years, including improving our payment channels with the introduction of an app, introducing improved and new functionality for our customers with an enhanced website and enabling them to apply for discounts online, and the eventual replacement of our camera network with high definition cameras.

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Tom has edited Traffic Technology International magazine and the Traffic Technology Today website since he joined the company in May 2014. Prior to this he worked on some of the UK's leading consumer magazine titles including Men's Health and Glamour, beginning his career in journalism in 1997 after graduating with a law degree from the London School of Economics (LSE).

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