or Failure of Revenue Control “The ‘wire loop’ located in the pavement is a


very critical part of the detection system. Standard house wire such as THHN absorbs moisture and easily develops leakage paths and shorts to ground. “Faulty loop wire problems and electrical con-


nections are the most common sources of loop detector problems. Changing electronics does not repair faulty wire insulation and/or poor connec- tions. Saving pennies on loop wire results in unreli- able detector performance and unhappy cus- tomers!!! “I highly recommend the use of ‘preformed


loops,’ manufactured in a controlled environment using correct materials, procedures and tools,” Pot- ter said. “Complete quality control during the man- ufacturing process is essential. “The best installation procedure is to locate


the loops in the proper area and then pour the concrete over them. If that’s not possible, they should be cut into concrete – loops cut into asphalt can be problematic. “As vehicles pass over the asphalt, it moves,


particularly during acceleration and braking in hot summer weather. The moving aggregate in the pavement cuts into the loop insulation. The softer the insulation, the sooner loop insulation failures occur. Preformed loops with tough high-temperature insulation have proven to survive very harsh environments,” Potter said. “There is no substitute for proper loop wire insulation. “The problem is that if a loop fails at a traffic signal, the ability


to move traffic is compromised, which results in delays and con- gestion. In a parking garage, a gate may not close, or worse, may close at the wrong time. “We can do some pretty amazing things with the electronics,


such as detecting tailgating and differentiating between cars, motorcycles, trash cans and steel-toed shoes, but if the loop itself fails due to poor material and installation, all the sophistication in the world is useless.” Potter noted that detectors in parking garages are used to


close gates after a car exits and to prevent gates from closing when a vehicle is present. They also are used to “arm” ticket dispensers so tickets cannot be issued unless a vehicle is present, as well as to “arm” card readers so a vehicle must be present before a card is read. “This prevents cards from having their ‘passback’ mode reset and allowing more than one vehicle to exit with the same permit,” Potter said. “More complex installations use detectors to ensure that


vehicles are traveling in the correct direction in lanes (more than one loop is needed for this purpose), and to ensure that the trans- action is complete before making a ticket valid or resetting a pass- back mode. “In this last case, an online system will issue a ticket when a car


is present, but the ticket will not be valid if the car does not com- plete the process by entering the garage. The vehicle must exit the loop at the dispenser and then exit the closing loop at the gate. This process could be critical in preventing improper issuance of tickets at airports, for instance, where new tickets can be swapped for those of long-term vehicles. In this case, consider-


For the best results, ‘float’ the induction loops in the concrete while it is wet so it becomes part of the garage. Here the loops are so installed with dotted lines showing their locations.


able revenue can be lost,” Potter said. “In multilevel parking facilities, vehicle detectors can be used


for counting, feeding information back to the central office and for driving floor displays informing drivers where space is avail- able. In stadium parking situations where lanes are periodically used, it is recommended that the loops be permanently installed in the normal manner, and that the electronics be housed in a box nearby where they can be unplugged and stored securely when not in use,” Potter said. Want to find out if your dispenser loop is working? Walk up


to the dispenser and push the button. If a ticket is issued, you have a vehicle detection failure. This is crucial to the revenue controls in your facility. Unfortunately, he said, a test at a gate usually occurs when the gate stays open after a car leaves, or worse, closes on a vehicle. “I know some manufacturers of revenue control systems are


of two minds concerning having loop detectors integrated into the gate controller electronics,” Potter said. “My feeling is that if loop detectors and controller electronics are independent, the end user has total flexibility in separately choosing operational features for each piece of equipment. This flexibility increases sys- tem value. “If a repair or upgrade is needed, separate components can


be removed and replaced without needing to replace an entire system. Also, due to the cost of a single integrated system, a spare may not be readily available for maintenance requirements. “Retaining flexibility is something to consider when making


the final decision on selecting equipment,” Potter said. Tom Potter can be reached at tom-sr@renoae.com.


PT JANUARY 2009 • PARKING TODAY • www.parkingtoday.com 43


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