In 2015, more than 10,000 people were killed in traffic crashes caused by alcohol- and drug-impaired drivers in the United States. Even though tremendous progress has been made in combating this problem through better laws, public education, and advanced enforcement techniques, the number of deaths in 2015 still increased from 2014. This increase highlights the need for effective law enforcement response to the issue, including strict enforcement of DUI laws. When impaired drivers are arrested, a vital piece of evidence is the chemical test. All states have implied consent laws, which require drivers who have been arrested for impaired driving to submit to a chemical test and provides sanctions for those drivers who do not. Despite the associated penalties, over 20 percent of drivers stopped for suspicion of DUI generally refuse to submit to a test.