Technological trends in road user charging and congestion charging systems

Technological developments have unleashed a multitude of tools for the owners of road user charging and congestion charging systems. It could be thought that this vast selection of tools would make system design and operation very easy, and that assumption is correct if the focus remains on the system, rather than individual technologies. A road user charging system or a congestion charging system is a complex structure that must work in conjunction with different technologies.

From the very beginning, when it was decided to make the users of a road pay for the service, the operator of the road has been facing the same three challenges:

• How can I identify the ones that should pay toll fare?
• How can the payment be arranged efficiently and securely?
• How do I treat the ones that don’t follow the rules?

Originally, the purpose of road toll collection was to provide income to the operator. In later years, authorities have found that road toll collection can also be used as an instrument to control the demand for roads, bringing an aspect other than revenue into the picture. Despite the purpose of the operation, the three challenges mentioned are the same.

Depending on the location of the system and the purpose for which the system is made, a toll collection system will be facing different environments. With the technology development in mind, one might believe that such systems will evolve into steadily bigger technological monsters. This might happen of course, but experience shows that the most efficient systems base their operation on fairly simple principles, focusing strongly on the key functions to support. Individual technological properties are of less importance than the system design, which keeps its focus in executing the functions effectively.

The enforcement challenge

When it comes to traffic, the road operator essentially has two options; either prove that a user was breaking the rule and then issue a compensation claim, or prevent the violation from occurring. The former can be done using a photograph, whereas the latter requires a physical obstruction; in most cases a barrier. As the use of barriers makes a very significant negative impact on the road’s lane capacity, this is only used when legal constraints require the road operator to do so. Because of this, most road operators would choose video images as the method for proving that the rules have been violated.

Video systems for enforcement purposes can be applied in many different ways. The most common solution is stationary cameras that take a photograph of each vehicle that passes illegally, but mobile units can also be used. A clear trend is the use of Automatic Number Plate Recognition (ANPR), where software automatically reads the symbols in the number plate. Of course, this makes post-processing more efficient; providing the ANPR software is working correctly.

Determining the applicable rules

The task of determining who should pay, and how much that would be, can be done with different techniques. Inspecting each vehicle’s identity manually, reading a ticket or card, reading the identity of a tag, or reading the number plate of the vehicle; the methods of working out who should pay (and how much), are numerous. With navigation systems available, it is also possible to determine payment liability through the use of geographical co-ordinates.

Settlement struggle

The method of payment is always of interest to the owner of the system. A large number of options exist, ranging from cash, bank transfers, credit cards and electronic cash.

All these tools should make it rather easy to create an efficient toll collection or congestion charging system. However, the risk related to the choice of technology is that choosing the wrong tools may cause the system to generate insufficient data, or perhaps worse, an excessive amount of data.

The use of the car’s number plate to identify the vehicle is tempting as all cars have number plates. An identification solution here can be combined with the equipment for enforcement, as the cameras will cover both functions. However, the drawback is that there is no guarantee that the plate is genuine and there is no way for the system to check if it is false. In places where fake plates represent a problem, the system will loose large amounts of money. Another tempting solution is the use of cheap radio frequency identification tags (RFID), as the cost of these are significantly lower than more advanced and secure DSRC OBUs. Again, the system operator will see lower investments, but will be facing potentially serious problems if RFID tags can be copied.

Another option is to use the car’s satellite navigation system to determine when the vehicle is within the boundaries of the toll system. This would be possible provided that the operator has a very clear opinion on how the data would be used. Running an application in the vehicles on-board equipment, it would be possible to execute the entire set of business rules for the system locally. However, this could cause problems if the equipment needed to be updated. Alternately, all position data could be sent to a central server facility for processing. That would require a seamless data communications network, a hefty data storage, and citizens agreeing to have all of their movements tracked.

Secrets to success

The common factor for all successful road toll collection or congestion charging systems is the fact that they have focused on the essential functions to be supported by the system, rather than picking the most hyped technology. Experts may discuss whether a thin or a thick GNSS client, or a fat or a slim OBU is the best option. But the fundamental questions to be answered is; ‘what should the system do?’ and ‘how can that be done efficiently?’

For all road user charging, congestion charging or road toll collection systems, one requirement is an outstanding common factor; the system must be reliable. In order to ensure this, they all make use of advanced security mechanisms. Operations of this kind include the handling of many transactions and large amounts of money. If, for some reason, reasonable doubt should arise with respect to whether or not the system is secure, the economical consequences could be serious. Thus, the operators of such systems require that all parts of the system are protected against unauthorised use; such as eavesdropping, duplication or repudiation.

The Portuguese Via Verde system relies primarily on the use of electronic DSRC OBUs for the purpose of identifying the vehicles that should pay the toll fare, and the enforcement is based on the use of video images. As an option, Via Verde offers manual serviced lanes with cash or credit cards. Payment is settled directly via the national bank system SIBS.

In London, the system is being extended so that it no longer exclusively uses video images to identify the vehicles, but also will offer the use of DSRC OBUs. The reason for this is probably because a secure electronic transfer from an OBU is less costly during the administrative central processing than a video image that will require manual control prior to charging the car’s owner.

The Norwegian AutoPASS system bases its operation on DSRC OBUs as the primary means of identification, and ANPR cameras as the second. Enforcement is realised using video with ANPR capability and payment is done via the road operator’s own co-ordinated subscription programme, ASB.

Stockholm chose to use ANPR cameras as the primary method of identification, due to legal constraints related to the fact that the fee levied in Stockholm is formally regarded as a tax. The camera system used in Stockholm is a highly secured system with a digital signature of each individual image. In combination with a voluntary option for using DSRC OBUs, and the fact that the number of fake number plates in Sweden is very low, the Stockholm Congestion Tax System is an effective solution to reduce congestion in the city.

The most successful road user charging or congestion charging systems are the ones where the road operator has not changed their requirements. After all, the technological investments for such systems are only a fraction of the revenue generated. Correspondingly, the owners of such systems are exposed to a significant risk if the technology is not working properly. As such, there are a number of very important properties for any technology that is to be used in this context.

• Security. The system must provide adequate protection against fraud, copying, eavesdropping or repudiation.
• Availability. The system must be affordable, easily accessible to the public, and have a technical stability that secures an almost seamless operation.
• Capacity. The technology must not disturb the driver or obstruct the free flow of traffic.

Keeping this in mind, it remains as important as ever to choose the correct tools for the task. However, the world is certain to see many other successes following the solutions in Stockholm, Portugal, London and Norway.