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Electronic toll collection

From Academic Kids

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FasTrak_transponder.jpg
Many ETC systems use transponders like this one to electronically debit the accounts of registered cars without their stopping

Electronic toll collection (ETC), an adaptation of aircraft "identification friend or foe" technology, aims to eliminate the delay on toll roads. It is a technological implementation of a road pricing concept. It determines whether the cars passing are enrolled in the program, alerts enforcers for those that are not, and debits electronically the accounts of registered cars without their stopping, or even opening a window.

Contents

Overview

In some urban settings, automated gates are in use in electronic-toll lanes, with 5 mph (8 km/h) legal limits on speed (and 2 to 3 times that as practical limits even with practice and extreme concentration); in other settings, 20 mph (35 km/h) legal limits are not uncommon. However, in other areas such as Houston, Texas, cars do go through electronic lanes at full speed. Enforcement is accomplished by a camera which takes a picture of the car and sends a fine to cars that pass through without paying a toll.

Factors impeding full-speed electronic collection include:

  • significant non-participation, entailing lines in manual lanes and disorderly traffic patterns as the electronic- and manual- collection cars "sort themselves out" into their respective lanes
  • problems with pursuing toll evaders
  • need, in at least some current systems, to confine vehicles in lanes, while interacting with the collection devices, and the dangers of high-speed collisions with the confinement structures
  • vehicle hazards to toll employees present in some electronic-collection areas
  • in some areas at some times, lines even to pass through the electronic-collection lanes

Even if line lengths are the same in electronic lanes as in manual ones, electronic tolls save registered cars time: eliminating the stop at a window or toll machine, between successive cars passing the collection machine, means a fixed-length stretch of their journey past it is travelled at a higher average speed, and in a lower time. This is at least a psychological improvement, even if the length of the lines in automated lanes is sufficient to make the no-stop-to-pay savings insignificant compared to time still lost due waiting in line to pass the toll gate.

Despite these limitations, however, it is important to recognize that throughput increases if delay at the toll gate is reduced (i.e. if the tollbooth can serve more vehicles per hour). The greater the throughput of any toll lane, the fewer lanes required, so expensive construction can be deferred. Specifically, the toll-collecting authorities have incentives to resist pressure to limit the fraction of electronic lanes in order to limit the length of manual-lane lines. In the short term, the greater the fraction of automated lanes, the lower the cost of operation (once the capital costs of automating are amortized). In the long term, the greater the relative advantage that registering and turning ones vehicle into an electronic-toll one provides, the faster cars will be converted from manual-toll use to electronic-toll use, and therefore the fewer manual-toll cars will drag down average speed and thus capacity.

In some countries, some toll-collection companies who use similar technology have set up or are setting up roaming arrangements between each other. This permits one to drive a vehicle on another operator's tolled road with the tolls that are incurred on that road being charged to the driver's toll-payment account that they have with their home operator. A best example of this is in Australia where a vehicle that has a CityLink e-Tag device can be driven to Sydney along the M5 South Western Motorway and pass through the toll barrier smoothly and quickly while that M5 toll is debited to the CityLink account

These factors herald more, and more effective, use of electronic tolls.

Technologies

Electronic toll collection systems rely on four major components, namely Automated Vehicle Identification, Automated Vehicle Classification, Customer Service, and Violation Enforcement. This section discusses each of these further.

The four components are somewhat independent, and, in fact, some toll agencies have contracted out functions separately. In some cases, this division of functions has resulted in difficulties. In one notable example, the New Jersey E-ZPass regional consortium's Violation Enforcement contractor did not have access to the Customer Service contractor's database of customers. This, together with installation problems in the Automated Vehicle Identification system, led to many customers receiving erroneous violation notices, and a violation system whose net income, after expenses, was negative, as well as customer dissatisfaction.

Automated Vehicle Identification

Automated Vehicle Identification (AVI) is the process of determining the identity of a vehicle subject to tolls. The majority of toll facilities record the passage of vehicles through a limited number of toll gates. At such facilities, the task is then to identify the vehicle in the gate area.

Some early AVI systems used barcodes affixed to each vehicle, to be read optically at the toll booth. Optical systems proved to have poor reading reliability, especially when faced with inclement weather and dirty vehicles.

Most current AVI systems rely on radio-frequency identification (RFID), where an antenna at the toll gate communicates with a transponder on the vehicle via Dedicated Short Range Communications. RFID tags have proved to have excellent accuracy, and can be read at highway speeds. The major disadvantage is the cost of equipping each vehicle with a transponder, which can be a major start-up expense, if paid by the toll agency, or a strong customer deterrent, if paid by the customer.

To avoid the need for transponders, some systems, notably the 407 ETR near Toronto, use automatic number plate recognition. Here, a system of cameras captures images of vehicles passing through tolled areas, and the image of the number plate is extracted and used to identify the vehicle. This allows customers to use the facility without any advance interaction with the toll agency. The disadvantage is that fully automatic recognition has a significant error rate, leading to billing errors. Systems that incorporate a manual review stage have much lower error rates, but require a continuing staffing expense.

A few toll facilities cover a very wide area, making fixed toll gates impractical. The most notable of these is a truck tolling system in Germany. This system instead uses Global Positioning System location information to identify when a vehicle is located on a tolled Autobahn. Implementation of this system turned out to be far lengthier and more costly than expected.

Automated Vehicle Classification

Automated Vehicle Classification (AVC) is closely related to Automated Vehicle Identification (AVI). Most toll facilities charge different rates for different types of vehicles, making it necessary to distinguish the vehicles passing through the toll facility.

The simplest method is to store the vehicle class in the customer record, and use the AVI data to look up the vehicle class. This is low-cost, but limits user flexibility, in such cases as the automobile owner who occasionally tows a trailer.

More complex systems use a variety of sensors. Inductive sensors embedded in the road surface can determine the gaps between vehicles, to provide basic information on the presence of a vehicle. Treadles permit counting the number of axles as a vehicle passes over them and, with offset-treadle installations, also detect dual-tire vehicles. Light-curtain laser profilers record the shape of the vehicle, which can help distinguish trucks and trailers.

Customer Service

Customer Service deals with maintaining customer accounts, posting toll transactions and customer payments to the accounts, and handling customer inquiries. In many respects, the Customer Service function resembles banking, and several toll agencies have contracted out customer service to a bank.

Customer accounts may be postpaid, where toll transactions are periodically billed to the customer, or prepaid, where the customer funds a balance in the account which is then depleted as toll transactions occur. The prepaid system is more common, as the small amounts of most tolls makes pursuit of uncollected debts uneconomic. Most postpaid accounts deal with this issue by requiring a security deposit, effectively rendering the account a prepaid one.

Violation Enforcement

A Violation Enforcement System (VES) is useful in reducing unpaid tolls, as an unmanned toll gate otherwise represents a tempting target for toll evasion. Several methods can be used to deter toll violators.

Police patrols at toll gates can be highly effective, as being stopped by the police is quite memorable for the violator. In addition, in most jurisdictions, the legal framework is already in place for punishing toll evasion as a traffic infraction. However, the expense of police patrols makes their use on a continuous basis impractical, such that the probability of being stopped is likely to be low enough as to be an insufficient deterrent.

A physical barrier, such as a gate arm, ensures that all vehicles passing through the toll booth have paid a toll. Violators are identified immediately, as the barrier will not permit the violator to proceed. However, barriers also force authorized customers, which are the vast majority of vehicles passing through, to slow to a near-stop at the toll gate, negating much of the speed and capacity benefits of electronic tolling.

Automatic number plate recognition, while rarely used as the primary vehicle identification method, is more commonly used in violation enforcement. In the VES context, the number of images collected is much smaller than in the AVI context. This makes manual review, with its greater accuracy over fully automated methods, practical. However, many jurisdictions require legislative action to permit this type of enforcement, as the number plate identifies only the vehicle, not its operator, and many traffic enforcement regulations require identifying the operator in order to issue an infraction.

Toll collection systems

Australia

Asia-Pacific

Canada

Europe

South America

United States

See also

External links

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