How often must the section of rail be tested in the field with the third rail tester?

The requirement for testing the section of rail with the third rail tester "at frequent intervals" is supported by the need to ensure safety and reliability in the functioning of the rail system. Frequent interval testing allows for early detection of any potential issues that may affect the performance of the rail infrastructure, which is crucial for maintaining operational integrity and preventing accidents. This proactive approach aids in addressing wear and tear, environmental impacts, or other factors that could compromise the rail system's functionality.

Choosing a specific timeframe like once a year or every month would not provide the necessary flexibility to respond to changing conditions in the field, nor would it ensure that any issues are identified and resolved in a timely manner. Moreover, relying solely on complaints for testing may lead to situations where critical safety issues go unnoticed until it is too late, undermining the proactive measures meant to ensure a safe and effective rail system. Thus, testing "at frequent intervals" aligns best with best practices for maintaining rail integrity and safety standards.