What would you recommend we deploy for such an application?
It really depends on what you are trying to achieve and the type of parking areas you operate. If you are trying to manage entry and exit points, and if only a defined group of people are allowed to park in a particular lot—say, a set number of office workers or apartment owners—then you could issue a high-frequency (HF) RFID card to each user, who would then present that card to a reader near the lot's entrance and exit. (He or she would likely have to roll down the window and reach out to present the card to the reader.)
You could also use passive ultrahigh-frequency (UHF) windshield tags and a fixed reader near the entry and exit points. The longer read range of passive UHF would enable the system to automatically interrogate the tag on the windshield and open for an authorized vehicle. However, you would need tags specially designed to work on windshields, and you might want them to be tamper-proof.
If you are managing an open parking area, without entry and exit gates, then you could implement passive UHF windshield tags and issue handheld readers to workers. The City of Hoboken, N.J., switched to this type of system in 2006 (see Hoboken RFID-enables Its Parking Permits). Parking officers employ handheld interrogators to read UHF RFID tags embedded in city-issued resident parking permits. Standing alongside a vehicle and waving a handheld, an officer can determine whether a car is legally parked with the proper permit. The process takes just a few seconds, saving the city time and money. Previously, officers might have had to spend a minute or more just trying to determine if a vehicle had a permit—and, if so, to locate it. Sometimes, the permit might not be positioned in the proper spot, or it might be hidden by tinted windows or other obstacles, adding additional time to the process.
If you are managing an open garage and simply want to help visitors find empty spots, there are RFID sensors that will do the trick. In 2009, the Ronald Reagan UCLA Medical Center, a new hospital on the UCLA campus, set up a network of sensors to monitor traffic within its garage. The goal was to make parking faster and easier for visitors and personnel (see UCLA Hospital Hopes Smart Garage Expedites Parking).
The monitoring system comprises infrared Wireless Sensor Network Modules from National Instruments (NI), mounted at the parking garage's entrances and exits, which are read every time a car drives by. These events are collected in NI's LabVIEW software application. The data is analyzed to determine the number of available parking spots on the monitored floors, based on the total number of spaces on that floor, as well as on the number of cars that each sensor detects entering or exiting.
The infrared sensors communicate using the ZigBee communication protocol, based on the IEEE 802.15.4 standard. The devices transmit their unique identification numbers, as well as the number of passing cars detected by the infrared sensors, at a low bit rate—up to 250 kilobits per second—and operate at low power to preserve battery life. The NI modules being used in the parking garage transmit at 2.4 GHz, and can operate for three years on four AA batteries when transmitting data once per minute.
Near Field Communication (NFC) technology can also be used to pay for parking. In 2011, the San Francisco Municipal Transportation Agency (SFMTA) deployed NFC-enabled technology at all 30,000 of its metered street-side parking spaces that allow motorists to pay for parking via mobile phones. With technology provided by PayByPhone, a driver can download and install an application to his or her NFC-enabled mobile phone, allowing that individual to pay for parking by tapping the phone against an NFC decal attached to the meter. In so doing, the driver can indicate that he or she has parked, and approve billing for that space using a credit- or debit-card number provided when the app was downloaded (see San Francisco Launches NFC Payment for All Its Metered Parking).
—Mark Roberti, Founder and Editor, RFID Journal
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