The best way to make sure a production line is working at maximum efficiency is to go and see it for yourself. This is the idea behind Genchi Genbutsu, part of the Toyota Production System.
Genchi Genbutsu (English: Go and see for yourself): The best practice is to go and see the location or process where the problem exists in order to solve that problem more quickly and efficiently. To grasp problems, confirm the facts and analyse root causes.
The Toyota Production System requires a high level of management presence on the factory floor, so that if a problem exists in this area it should be first of all correctly understood before being solved. The nature of the phrase is less about the physical act of visiting a site but more to do with a personal understanding of the full implications of any action within an environment as a whole.