Substance abuse in the workplace can cost companies valuable time and money. Workers who abuse drugs and alcohol tend to be less productive, miss more work days, are more likely to injure themselves or others, and file more worker's compensation claims. One way that companies can protect themselves is to implement a drug and alcohol testing policy. Such a policy can help screen out alcohol or drug abusers before they become employees. It can also protect companies from negligent hiring claims that may arise from alcohol- or drug-influenced violence in the workplace. In some cases, employers may be legally required by federal or state law to test applicants who are filling high-risk or safety-sensitive job positions. For example, all railroad and public transportation employees must be tested for drug and alcohol use periodically. When enforcing a drug and alcohol testing program, companies must be sure to comply with all federal and state laws regarding how and when testing procedures can be carried out. Most of these laws will require companies to notify prospective employees in advance, especially on job applications, when and under what conditions they may be tested. Employers who prohibit substance abuse in the workplace generally have the right to deny employment to applicants or terminate employees who test positive on a drug or alcohol test. Companies, however, may be subject to discrimination or privacy violation claims if testing procedures are carried out inconsistently and unfairly among employees.