It’s not clear whether evaluations improve performance or safety. But it does provide you with a good system to document performance. If you conduct evaluations, tell it like it is. If something’s not good, give examples, set goals, and follow up. Warn the employee that failure to improve might lead to disciplinary action. These need to be systematic and ongoing. Don’t be excessively lenient, don’t avoid the ends of the rating scale, and base it on the whole evaluation period.