Tolling as a method of financing the transportation system is becoming common incorporating several technologies, collectively called Electronic Toll Collection (ETC). Open Road Tolling (ORT) with all-electronic toll collection, is now the preferred practice, being more efficient, environment friendly and safer than manual toll collection. Explains, Khali R. Persad, Ph.D., P. E., Assistant Director, Research Engineer at Center for Transportation Research, University of Texas at Austin.
There are three main reasons why tolling, or road pricing, is implemented. To recoup the costs of building, operating and maintaining the facility, to moderate the growth in demand on the transportation system and to encourage more use of public transportation or to place a price on limited roadway space in proportion to demand. Electronic toll collection is now the preferred mechanism for tolling. Among the benefits of ETC are:
- ETC lanes improve the speed and efficiency of traffic flow and save drivers time. Manual toll collection lanes handle only about 350 vehicles per hour (vph), and automated coin lanes handle about 500 vph while, an ETC lane can process 1200 vehicles per hour.
- As a result of better flow, congestion is reduced, fuel economy is improved, and pollution is reduced.
- Increased revenue, time savings, faster throughput and better service attract more customers, thus increasing revenue.
- Reduced accident rates/ improved safety because of less slow-and-go driving.
- Increased efficiency of roads because of better distribution between tolled and non-tolled routes.
The initial costs of implementing ETC or converting a manual toll facility into an ETC can be quite high. There are also significant operational and maintenance costs to an ETC system that are difficult to predict or to figure into calculations. Most systems which have implemented ETC require motorists to pay a security deposit, pay a monthly fee and in some cases keep a minimum balance in his account. However, not only are the costs per transaction usually lower in an ETC system, the number of transactions are far higher than in a manual system. Additionally, the number of people required to operate an ETC system is far fewer than required for a manual toll collection system. Overall costs per transaction, therefore, shrink significantly.
Implementation and Operation Challenges:
- Insufficient knowledge of ETC technology by consumers who fear their movements will be ‘tracked’.
- Interoperability issues between different systems which raise costs.
- Reconstruction of highways to include ORT lanes, build gantries, or dismantle existing manual toll collection booths.
- Non-paying users—because of minor shortcomings of ETC technology, some users may slip through the system without paying.
Electronic toll collection poses a threat to privacy because the systems record when specific motor vehicles pass toll stations. From this information, one can infer the likely location of the vehicle’s owner or primary driver at specific times. Using e-cash and other modern cryptography methods, one could design systems that do not know where individuals are, but can still collect and enforce tolls.
Components of ETC
Electronic toll collection requires several components in order to complete a transaction. The two most important components are vehicle recognition and account identification. Vehicle recognition may be accomplished through in-road and overhead sensors, cameras, vehicle-to roadside communication or combinations of these. Where vehicles are charged differently according to class, vehicle classification is part of vehicle recognition. Account identification is accomplished by tying the vehicle ID to a user account, usually through a relational database.
In-road Sensors: Sensor systems may be subsurface, roadside or overhead. Inductive sensors embedded in the road surface can determine the presence of a vehicle. Treadles register a count of 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. Sensors can also detect gaps between vehicles to provide information on the number of vehicles crossing a location.
Overhead Cameras: The use of overhead cameras for vehicle identification in tolling is referred to as video tolling, done by means of license plate identification/ recognition (LPI/R). As a vehicle passes through, cameras on overhead gantries take a picture of the license plate. Optical Character Recognition (OCR) software is used to read the picture of a plate, and the number is checked against a database to find the owner associated with the vehicle. Video tolling is usually used in conjunction with other systems as a means of enforcement for non-toll account vehicles. Despite its wide use, LPI/R has some shortcomings:
- Poor image resolution, usually because the plate is out of focus.
- Blurry images, particularly motion blur, most likely at higher vehicle speeds.
- Poor lighting and low contrast due to overexposure, reflection, shadows or plate background color or style.
- An object obscuring (part of) the plate, quite often a tow bar, or dirt on the plate.
- A different font, vanity plates, different plate styles, as in Federal vehicles.
- Circumvention techniques (such as reflective plates)