By using the same metric they user to evaluate engineers, they can measure if drivers are meeting expectations. Are they meeting expectations or causing problem

By using the same metric they user to evaluate engineers, they can measure if drivers are meeting expectations. Are they meeting expectations or causing problems in the workplace? If you get off work and take a toke, it may not affect your performance vs having a drink. Even occasional users can be banned from work because it stays in the system longer than any other drug. It would be interesting to see a study on how substance use affects employee performance, including nicotine and alcohol. Clear evidence of correlations with earning potential may convince people to reduce or eliminate use. If there is a degrade with pot use and Amazon is willing to pay less for it, so be it.