Automatic License Plate Recognition (ALPR) is not the only technology available for vehicle recognition or vehicle detection. In road user charging applications, such as tolling, weight-in-motion, and environmental zones, RFID tags are also a commonly used technology. In access control applications such as parking ticketed or card-based systems are still prevalent. Each has its merits depending on the application and the requirements and wishes for it. In fact: some work better together in a mixed deployment. In this short article, we will review these different competing technologies, how they fit in given different considerations.
1. Accessibility or Ease of Use
Applications with a vehicle charging application that needs to be publicly accessible or have a varying audience (for instance seasonal, in contrast to commuter traffic) benefits from an in-person service, ticketed access, or technology with a low-barrier to use. This is relevant when volumes are high or have a high degree of variability. ALPR provides a simple solution that is frictionless and can be used in a free-flow scenario.
In contrast to a system using a physical token -whether this is a ticket, RFID tag, or cash- ALPR greatly improves flow and reduces administrative complexity. Not unimportantly: free-flow road user charging or access saves fuel and reduces pollutants caused by idling and crawling (stop-start) traffic and helps contribute to sustainability goals.
With just the digital camera image and roadside information of the vehicle and actual license plate needed for recognition, the service can be fully integrated into a back office and payment processing system. ALPR is an unobtrusive technology that can be easily used and managed by patrons. When connected to a public vehicle plate registration system, ie. DMV, a completely automated billing system can be achieved without patrons ever needing to enroll or wait for service – at the toll booth or customer support.
In countries where privacy is strictly observed, access to vehicle owners by license plate is not publicly accessible. However, given there is no physical token, using a visible license plate and camera makes enrollment easier compared to a scheme that requires possession of a physical tag or token for recognition. Users can simply choose to share their payment details and license plate number. This also makes one-time payments based on plates much easier especially in popular tourist areas.
2. Space is a Premium
Very practically, consider the amount of space you have or are planning to use for the charging infrastructure. Gated or stop-and-go systems require valuable real estate for the gate and payment
infrastructure. Examples include ticketed parking or pay-by-card or cash toll booths. In addition, they are not frictionless adding the potential to cause jams and backups. Which in turn requires additional buffering space to cope with excessive traffic volumes. Similarly, a densely built urban environment may not even afford the luxury of having space-hungry road user infrastructure.
Frictionless technologies like ALPR or RFID tags help reduce infrastructure costs and require much less real estate than other technologies. Cameras used for ALPR or RFID reading equipment require a suitable mounting point with appropriate access for maintenance. With space as a premium asset, a pole-mounted reader or camera minimizes the footprint for operation.
When it comes to space, ALPR and RFID tags are similar. What sets them apart is the ability to increase the scope of recognition requirements, e.g. add functionality such as the direction of travel or speed. ALPR and vision technology also allow determining the actual situation rather than solely relying on the information carried by the RFID. This prevents borrowing tags or changing the information on the tag itself. RFID also brings a significant logistical burden to distribute and administer all the tags or sign up to the system.
3. Consider Reliability
Reliability can be seen as either the preconditions for a technology to work well and how reliable the results are. We will address both here. The presence and quality of data connections as well as the accuracy of road user recognition influence what options are available to an integrator or operator. Ticketed or toll booth systems offer anonymous and direct transactions that can happen without connectivity. That is, without taking into account maintenance, service personnel, and service hours.
ALPR and RFID tags require a physical asset linked to details communicated between the service backend and roadside camera. Its use, therefore, requires either a local or remote network to operate. Small operations -especially in surveillance- do not require a remote backend and can be self-contained. Larger installations with an enrollment requirement, centralized connection to a DMV, or remote manual review, need reliable connections to match different points of recognition and reliable billing.
Recognition rates for ALPR-based products vary from country to country and can vary between camera setups. In countries with complex plates, automation will typically sit between 80% – 90% whereas countries with plates optimized for reading this may go well beyond 98%. The manual review effort for recognitions that cannot be performed automatically can easily be justified by the relatively small workforce and minimal administrative burden.
Commonly achieved recognition rates that include manual review reside between 99.5% to 99.98%. While RFID technology is usually preferred due to the high automation rates that it can achieve it provides no way of knowing whether the tag belongs to the vehicle. Fraud and misuse of tags are much easier than video technology. In modern systems, you will find two methods (mixed-mode) of recognition to avoid missing vehicles without tags or intentionally misusing them. More so they will move over slowly to video-only given its other advantages in the longer term.
4. Long-Term Vision and Changes
Your choice of technology can influence or dictate what revenue opportunities you have. New revenue streams can be capitalized when flexibility in technology is offered. Or, offer new income sources without high switching costs or complex upgrade paths.
Both RFID and ALPR can be used for average speed checking systems, with a majority of systems using ALPR on public roads to reduce overhead. Vision technology, such as traffic cameras can be upgraded beyond license plate recognition. This offers a large potential beyond what RFID technology or manual processes can offer. The initial investment in road-side cameras and/or centralized recognition can be extended with little effort. A prominent example is model-make recognition (MMR), color recognition, and direction of travel offered by most modern ALPR systems. Further detection options that are becoming more prominent are seatbelt wearing and mobile phone use detection behind the wheel.
With ALPR in Low Emission Zones, large trucks and buses can be flagged and fined by using vehicle type recognition offered through a model-make recognition extension (MMR). Less obvious opportunities exist too. For instance; parking different fees can be charged on vehicle type (for instance a large SUV or small car), or offer battery top-up fees for models that accept electric charging. Similarly, the direction of travel or color in toll road use can be useful for traffic enforcement officers or automatically signal for wrong-way drivers to other users on overhead signs.