Highest inspection rates occur where loop operation is critical to the operation of other deployed traffic management systems. In many instances loop maintenance costs are sufficiently high that malfunctioning loops are replaced outright, without any diagnosis of the cause of failure. Because loops have been deployed extensively, consistent installation recommendations and primary causes of loop failure have been documented. Saw cuts should also be of uniform depth. Loops should be properly sealed.
Many factors contribute to physical loop failure.
Sharps bends in loop corners have also been found to cause problems, such that the insulation deteriorated or was broken. Sealent failure poses additional problems. Once the sealant fails, the loop may become exposed or foreign materials may infiltrate the cut. In many cases the loop was found to have floated to the top of the cut, either before the sealant could cure or because it remained plastic. Other common sources of loop failure include poor installation and maintenance procedures, damage from utility repair or construction, lightning surges, detuned amplifiers, and corroded splices or wires.