Currently limited land availability, scarce funds, and social and environmental concerns prevent many agencies from adding new freeway lanes. The combination of these factors is forcing transportation planners and engineers to explore new ways to more effectively operate the existing transportation network. Thanks in part to the enabling capabilities of ITS technologies, the use of managed lanes is one such concept that is being used successfully across the country.
A managed lane facility requires effective enforcement policies and programs to operate successfully. Enforcement of vehicle-occupancy requirements, use by authorized vehicles, or proper toll collection is critical to protecting eligible vehicles' travel-time savings and safety. Visible and effective enforcement promotes fairness and maintains the integrity of the managed lane facility to help gain acceptance among users and non-users.
The "Enforcement Issues on Managed Lanes," research report draws on international examples to provide and overview of successful deployments of ITS technologies in enabling enforcement on managed lanes.
In order for a managed lanes facility to operate successfully adequate enforcement is needed. As manual enforcement requires abundant resources and high costs, many agencies are looking to a variety of automated strategies to both enable and enforce tolls on managed lane facilities. Automated enforcement of managed lanes uses several ITS components, including: automated vehicle identification (AVI), license plate recognition (LPR), electronic toll collection, and image capturing technology. Successful enforcement of managed lane facilities requires that enforcing agencies have the ability to identify specific vehicles and, when necessary, determine the number of vehicle occupants. Some lessons include:
- Collect tolls electronically using transponders in conjunction with AVI. Electronic transponders used along side AVI systems provide a reliable method for quickly collecting tolls on managed lanes. With lane discrimination technology, AVI can also be used to assess lane specific tolls, ensuring that transponders ignore signals from AVI readers in adjacent travel lanes. AVI is also useful for collecting travel time data, which can be used to study traffic management strategies, detect incidents, and reduce congestion.
- Enforce toll violations of vehicles without transponders by installing license plate recognition (LPR) systems. LPR systems are used widely for automated enforcement of managed lane facilities that assess tolls. When a toll violation occurs, the LPR system activates. A violator's license plate number is then stored locally, or it is transmitted to a management center via standard dialup telephone lines, cellular links, radio transmitters, and Ethernet networks. More advanced systems can interface with the image-capture system at the remote enforcement site to process digital images of the violator's license plate, access motor vehicle registration data, and print and issue violation tickets by mail. This technology excels in reliability, with recognition rates reportedly up to 99.5 percent. Such results can even be expected during severe weather conditions, including lightning storms.
- Void of any toll plazas, the 407 highway express toll route (ETR) in Toronto relies entirely on LPR systems to enforce toll collection. The LPR system in Toronto is able to automatically identify roughly 80 percent of vehicles not equipped with transponders. Staff reviews digital images of the other 20 percent in an effort to identify vehicles for billing. Approximately 6 percent may not be billed at all, due mainly in part to the lack of extradition agreements between the vehicle owner's home province or U.S. state.
- Use automated enforcement to determine compliance with vehicle occupancy requirements in HOV/HOT lanes. This method of enforcement requires observation of the interior of vehicles to check the appropriate number of occupants. A typical strategy for this includes installing three or more cameras with artificial lighting sources to capture the front windshield image, the side window image, and the rear license plate image. The semi-automatic review process notes when a violation has occurred and electronically saves the images of the vehicle's interior and it's license plate information.
- A semi-automated HOV enforcement and review system has been tested in Dallas, Texas using the above strategy. The system proved to be effective for mailing HOV educational information to suspected violators. The test results noted that use of the system for actual enforcement screening required various enhancements such as better quality video cameras, reduced video signal transmission loss, additional camera views, and better license plate recognition for vehicle identification. Additional camera views would enhance the system; however, there would still be some difficulty in capturing images of small passengers or children in car seats. Obviously, vehicles with tinted windows would also pose a problem to the system.
- Consider using bar code readers in place of AVI. High-speed bar code readers have been conceived as a potential replacement for AVI tags used for tolling passenger vehicles on managed lane facilities. This system uses a technologically advanced camera with pulsed infrared illumination combined with an extremely fast shutter speed allowing crisp images to be captured at highway speeds. Computer software has been developed to examine each field of video, at a rate of 60 frames per second, and determines if a bar code image exists. When a bar code image is detected, the image is electronically cut out of the larger field of view and read by the bar code reader. A bar code system of vehicle identification could provide the same information as other available AVI systems.
These lessons advance the goals of ITS by outlining how ITS may be applied in manages lanes to create more efficient, reliable, and accountable toll collection and enforcement processes, as compared to traditional methods. Transponders used in conjunction with AVI or bar codes are efficient in ensuring tolls are paid without causing further congestion. Where vehicles are not equipped with transponders, LPR systems have proved to be reliable at assessing tolls, without having to manually issue a charge. Lastly, cameras have proven to be effective at determining compliance with vehicle occupancy requirements in HOV and HOT lanes, though there are improvements to be made. Agencies deploying ITS in managed lane facilities are likely to experience medium to high up-front costs, along with low levels of traffic delay during initial construction. Nonetheless, the long term benefits associated with the enhanced performance of the system outweigh the initial up-front costs. Initial planning should focus on the immediate needs of managed lanes facilities, and how ITS can be implemented to meet those needs. This requires an element of understanding of existing technologies and their availability.
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