The words "trial operation" and "startup" can often be seen in many engineering projects. What do they mean?

Large construction site with many people and chaotic environment. After installation and debugging, some equipment needs to be put into trial operation, that is, trial operation has certain risks. In order to attract people's attention and avoid safety accidents, eye-catching signs are often hung

This is what you said: "You can often see the words" test run "and" driving "."