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Urban Road User Charging Online Knowledge Base

What Do We Know About Technology?

Charging, payment and enforcement

The traditional cash based toll collection systems combine charging and payment into one event, simply the transfer of cash from the road user to the toll collection attendant at the point of payment.

For electronic charging methods, we need to differentiate between charging and payment. Road usage and payment are usually separated in time. The charging process uses information relating to the vehicle’s passage to establish the amount due. Payment is the obligation of road users (or account holders) to transfer funds to the scheme operator, or to an intermediary established to accept fees relating to road usage. A driver may either prepay or post pay for road usage. This separation of charging and payment that technology has enabled is a huge convenience for drivers as well as for operators.

The charging and payment processes are strongly linked to the enforcement process, regardless of the choice of charging technology. Enforcement action is only needed when the user fails to pay, but this in turn requires information on the level and detail of the unpaid charge. Both charging and enforcement must rely on capturing evidence of a vehicle’s presence at a specific location and at a specific time. In an urban charging scheme, this would be based on digital imaging systems which capture evidence of a vehicle’s identification and presence.

There are concerns being expressed about data privacy, the agencies that might have access to journey and vehicle data, and the uses to which it might be put (Royal Academy of Engineering, 2006). Privacy also means that no unauthorised party should be able to eavesdrop on data transferred over communication links (ITS United Kingdom, 2007). In practice, the latter problem is solved by the use of data encryption; only those parties authorised to do so acquire the data in “clear” format.

Privacy is a right protected by national laws, and is the exclusive concern of Article 8 of the 1998 Human Rights Act (Harle and Beresford, 2005). Any personal data stored for the purposes of maintaining a URUC account is covered by national data protection acts and may not be divulged to any other party. According to ITS United Kingdom (2007), the following requirements relate to retaining user privacy:

  • All personal data must be stored, processed and when required destroyed in a secure fashion in line with the Data Protection Act.

  • Only those elements of personal data required for the purposes of subscribing to a RUC scheme should be requested by the RUC operator.

  • As soon as personal data is not needed by the RUC operator (and any other regulations relating to the retention of auditable information have been met) it should be destroyed.

  • Only authorised personnel should have access to personal data.

  • If personal data is transferred between sub-systems of a RUC scheme then it should be protected from eavesdropping. 

The main charging options
There are three main options for charging namely (1) manual, (2) licence and (3) electronic. The primary electronic technologies for the measurement and recording of road use for the purpose of charging can be subdivided into three classes namely (3a) ANPR, (3b) DSRC and (3c) GNSS/CN.

(1) Manual toll collection / Automatic coin collection machines

The operation of point-based road pricing schemes in the past was mostly based on manual toll collection or automatic coin collection machines at toll booths. An advantage was that it offered a high level of reliability and enforcement. It was a simple, effective and well accepted technology, but costly.

However, since vehicles had to stop, serious congestion was often created around the toll collection areas, which were space consuming as well. Also, this system is less appropriate for (variable) congestion charging and for large urban areas where roads have many exits.

(2) Paper licences: Point (entry) or area based

This is also essentially a simple technique with low implementation costs, but it is difficult to administer and enforce. It is well known from the first-generation Singapore Area Licensing Scheme and the initial Bergen toll ring of 1986.

A major disadvantage is that there is a real limit to the number of charging classes that can be accommodated. Further, the distribution and purchase arrangements are difficult, and enforcement is not easy.

(3) Electronic

It can be argued that the three electronic technologies described in this section are not competitors, but should be regarded as complementary: DSRC permits vehicles to be identified and localised for enforcement purposes, GNSS/CN can be used for distance-based measurement, and ANPR can be used to identify occasional users and to capture image-based evidence sufficiently reliably to be acceptable in court for enforcement purposes (ITS United Kingdom, 2007).

(3a) Automatic Number Plate Recognition (ANPR) / Virtual licences

ANPR uses optical character recognition (OCR) on images taken by cameras. This is a type of technology, mainly software that enables computer systems to read automatically the registration number of vehicles from digital pictures. The pixels of the digital image are then transformed into the ASCII text of the number plate. This is the same technology that lets you scan paper documents and turn them into electronic, editable files.

Usually, images of the licence plates of vehicles that should have paid the charge are recorded, interpreted using a computer-based OCR (Optical Character Recognition) system, and then compared to a database of registered users. The owners of those vehicles for which no charge has been paid are identified through reference to the national vehicle registration system, and enforcement action initiated. However, it does not have to be a requirement that users should pay in advance, i.e. before the transport service is used. The user may have a deadline to post pay for the service.
This is especially convenient for occasional users, whose vehicles are not already registered in a database before the service is used. ANPR has the advantage of being an established technology.

The London congestion charge scheme is an ANPR system. It uses hundreds of cameras, both stationary and mobile units, and ANPR to help monitor vehicles in the charging zone. The advantages are that enforcement operations have no impact on traffic flow, and the system provides photographic evidence to support enforcement proceedings. Also, this system is space saving in comparison with entry points / toll collection areas. However, ANPR requires signs and cameras which can cause problems in historic urban centres.

(3b) Dedicated Short Range Communication (DSRC)

Electronic fee collection based on DSRC is a common technology used throughout the world by toll road operators. On-Board Equipment (OBE) like a tag is mounted on the vehicle’s windscreen and communicates with road side equipment (see Figure 1 2). Tags are activated by a roadside transmitter, which sends a signal to the tag; the tag then responds with its identity. This response is read by an associated receiver at the roadside, enabling a charge to be added to or deducted from a centrally held credit or debit account. Active tags can also hold funds on inserted smart cards required to pay the charge.

DSRC can be used with a variety of charging concepts, including entry and area licensing, cordons, cells and screen lines. Tags make account management easier but require more street furniture than ANPR alone, and require vehicles to be fitted with equipment. DSRC charging points are now being optimised concerning physical size and mounting possibilities. The new requirements from London concerning roadside equipment in urban areas have been one of the main driving forces for suppliers to compress their equipment down to a minimum.

Both DSRC and GNSS/CN (see below) systems are based on OBEs (tags) mounted in the vehicle. There are two types of OBEs; passive and active. A passive tag is an OBU that is not working as a sender until awakened by the roadside equipment. Active OBEs are equipped with a power supply, using a battery for the small and simple tags in DSRC systems and the vehicle power supply for GNSS/CN due to its more complex OBEs, which have interfaces to GPS, sensors, tachometers, IC-cards and displays.

(3c) Global Navigation Satellite Systems/Celluar Networks (GNSS/CN)
GNSS/CN systems are also often referred to as Autonomous Electronic Fee Collection (EFC) systems. GNSS were developed by the US and Soviet governments for military purposes, but a wide range of civil applications have been developed for the US GPS. GPS is already widely used by truck operators for tracking of location of vehicles, and in Germany and Switzerland for distance-based charging of heavy goods vehicles. The on-board unit combines a GNSS location system and a communications link, with a digital map either on-board or in the “back office”. The vehicle’s position is used to identify the road segment and thus the correct charge can be assessed.

A major advantage is that no street furniture is required for charging, although infrastructure for enforcement may still be required. In Germany, which has the only operational GNSS/CN charging scheme currently in use, compliance checking (enforcement) is performed by DSRC at fixed gantries as well as with mobile and hand-held enforcement equipment. Also, the roadside infrastructure uses camera systems for ANPR in order to detect the vehicle status and validate payment (ITS United Kingdom, 2007).

Early experience with GNSS/CN showed operational problems with “urban canyons” in dense high rise urban environments, and parallel and close highways. This can be improved by using “map-matching” techniques and inputs from sensors such as accelerometers and the odometer. The GIROADS Project (Cosmen, 2008), a reference project in Europe for GNSS road applications, states that lack of signal is today a minor issue due to high sensitivity receivers. However, GNSS has weaknesses, especially the random position errors that can be large from time to time and lead to incorrect charging.

GALILEO, the European global navigation system, will be interoperable with GPS and GLONASS and it will provide a highly accurate global positioning service under civilian control. The availability of these new satellite constellations will improve matters by providing better multipath performance, improved signal acquisition, signal integrity and real-time positioning capability. Most important for URUC systems will be the overall improvements in heavily built-up areas and urban canyon environments.

Estimates of when GALILEO will be fully operational vary between 2013 and 2015. When it is fully deployed it will consist of 30 satellites (27 operational + 3 active spares) in three circular orbits, providing good coverage even at latitudes up to 75 degrees north (which corresponds to the North Cape) and beyond.

GNSS-based charging enables the introduction of road pricing on the entire road network. This makes it possible for governments to withdraw fixed taxes and to avoid increased use of smaller roads, which may be free of charge when using other systems. GNSS can be regarded as a cost effective and flexible technology for meeting the challenges of combining interurban and urban road charging.


From a user’s perspective, interoperability would mean “Single box, single contract, single invoice” (Engdahl and Oehry, 2004). As a minimum, technical compatibility is required, so that an OBE from one supplier interacts correctly with roadside equipment from another supplier. A road user wants to be able to drive through several different charging schemes without needing to have multiple OBEs on their windscreen. Also scheme operators want to purchase equipment from different suppliers, stimulating competition and allowing greater purchasing flexibility (ITS United Kingdom, 2007).

To ensure interoperability, two more levels of agreements are required in addition to technical compatibility: Procedural solutions (roles of the involved entities, data exchange and clearing, handling of classes and exceptions) and Contractual agreements (who is responsible for what? who pays for what? who owns the system?).

Interoperability is taking a long time to achieve, because historically there was little interest, and because the problem is very complex. Firstly, interoperability does not seem to pay commercially. Unlike in mobile-phone roaming, users are not prepared to pay a substantial amount for the extra service. The interoperability requirement is therefore driven more by governments, the EC and by EU research projects, rather than by toll operator initiatives. Secondly, the problem is very complex because electronic fee collection differs widely in each country; in charging concept, in technology, in classification and tariff structures and in legal and institutional background.

The European Directive 2004/52/EC on interoperability defines the European Electronic Toll Service (EETS). It establishes the conditions necessary to ensure a European electronic toll service that is interoperable at the technical, contractual, and procedural level. According to the Directive, all new electronic toll systems in Europe must use one or more of the following technologies:

DSRC (5.8 GHz microwave)

  • GNSS positioning systems (GPS and GALILEO)
  • Mobile communication (CN) based on GSM-GPRS standards

The EETS Directive only applies to systems with on board equipment, thus excluding the ANPR-based London and Stockholm schemes. However, it will have a major impact on the technology to be used in URUC systems, which will be required to be interoperable with other RUC systems when EETS comes into force. Further details of the importance of technical interoperability and standardisation are given in Appendix B.

The Norwegian AutoPASS DSRC based charging system is an example of a charging system which is interoperable nationally. It has been in operation since 2004 and now involves more than 25 project sites, of which 6 are urban toll ring systems. Regardless of where the passage is made, the passage will be registered and charged to the account of the toll operator where the driver has a contract. This contract can be based on either pre or post payment of charges.

Since March 2007, the Nordic Interoperable Tolling Systems project (NORITS) has defined and implemented the EasyGo service (see Trondsen, 2007). It is a joint initiative between road authorities and toll road operators in the Scandinavian countries. The service makes it possible for users of toll collection systems and some ferry crossings in the Scandinavian countries to use only the OBE issued by their local toll operator. Payments are administered by the local issuer.

A number of options and payment channels exist for the transfer of funds between the user of electronic charging and the scheme operator. For instance, the London congestion charge can be paid online, by SMS, by phone, at a shop, at a self-service machine or by post. In general, the transaction process is easier and faster for registered users, and some options like SMS and phone require the user to register. Advantages for registered users are that they can view their payment history online, and they receive a Fast Track card for faster payment online, over the phone and at retail outlets.

In Stockholm payments can only be made retrospectively (post-payment), and there is no option to pay at the charging points. During the trial, payment was to be registered in the congestion tax account no later than five days after the passage. This was later extended to 14 days, and additional payment options were made available as time went along. Still, more than 70% of the congestion tax was paid by direct debit, followed by payment at kiosks and retail outlets as the second most common payment method. Internet payments using charge cards, or bank giro, constituted only a small fraction of the total payments (Melander, 2008).

During the permanent scheme, from August 2008, monthly post-payments by invoice were introduced. This is regarded as a customer-oriented improvement as well as being necessary in order to reduce transaction costs. Possibilities to pay manually at kiosks have been removed.

In the Norwegian URUC schemes, the options of manual payment at the charging points (manned or unmanned) as well as pre- or post-payment arrangements have usually been available (see Chapter 3 for an example from Trondheim). The Oslo toll ring was converted to no stop, automatic operation only, as from 2nd February 2008. Manual toll booths and coin machines were removed. This meant no real change for AutoPASS tag holders, since they could still choose between pre- or post-payment agreements. Cars without a valid tag are detected by the ANPR enforcement system and they can choose between paying within three days at certain petrol stations, paying by SMS or they receive an invoice when the amount due has reached about € 12.

Enforcement is the term used for systems and procedures to ensure that road users follow scheme rules. A charging regime cannot exist without enforcement. Enforcement is a process involving well-defined procedures, human resources and enabling laws, in addition to a mixture of technologies. As a minimum, an enforcement strategy needs to be based on three fundamental objectives:

  • Compliance: To ensure that charging policies and payment rules are followed by all road users.
  • Deterrence to non-payment: To inform and raise awareness of scheme requirements to reduce the temptation to evade payment.
  • Revenue recovery: To ensure that the fees that are due are paid by road users and protect the revenue stream.

Depending on the nature of the scheme, there are three main areas which may be enforced or controlled; non-payment of fees, non-compliance with permissions or local regulations, and mismatch between declared and measured vehicle parameters. To enforce an automatic road pricing scheme in an urban area, one cannot rely on a simple technique like physical restraint by barriers such as sometimes used on tolled motorways. Also, simply manually noting licence plate details is another means of enforcing, but this would be impractical for a heavily used and widespread system.

A primary requirement is that evidence of a vehicle’s identification and presence in the charging area at a certain time needs to be captured. Fortunately, all vehicles are required by law to display a licence plate on the front and rear of the vehicle, in most European countries. A widespread technology for enforcement is therefore to use automatic number plate recognition (ANPR).

The role of a central system

The central system can be defined as the IT and core services on which charging, enforcement, and all external interfaces depend. As such, it can be considered an integral part of the business system, described in detail in the next chapter. The central system plays a key role in enabling an effective business operation for road user charging. The functions that comprise a central system are sometimes referred to as front and back office operations. The functions can be split into the following areas:

  • Account registration and fulfilment, for instance supplying users with OBEs.
  • Account management and customer relationship management.
  • Charging data capture and collection.
  • Enforcement, including revenue recovery.
  • Systems management and reporting.
  • Payment services.
  • Interfaces to public agencies and specialist service providers.
  • Provisions for data security and breakdown recovery.

These functions may be located at one place, or they may be distributed across many physical sites and between several service providers. In sum, a central system is a mixture of functions and administrative processes that follow prescribes business rules, in order to create predetermined outputs that meet quality of service expectations (see Chapter 5).