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The recommended practice for an in-trip check is to perform it within the first 25 miles of travel and then continue every 150 miles or every three hours thereafter. This protocol is designed to ensure the safety and operational integrity of the vehicle throughout the journey. Conducting these checks at these intervals allows the driver to monitor critical systems such as brakes, tires, and load security, helping to detect any issues that may arise during travel before they develop into serious problems.

This practice is crucial as it helps to maintain the vehicle in safe operating condition, thus ensuring not only the safety of the driver and passengers but also other road users. Regular checks can prevent accidents caused by mechanical failures or other issues related to vehicle performance.