Researchers who studied more than 18,000 fatal two-vehicle accidents in Texas and around the country discovered that the drivers responsible for causing the crash were more than twice as likely as the other motorists involved to be under the influence of opioid drugs or alcohol. The study, which was published in the medical journal JAMA Network Open in February 2019, was based on Fatality Analysis Reporting System data. The FARS database is maintained by the National Highway Traffic Safety Administration.

The most common cause of the fatal accidents studied was drivers who failed to stay in their lanes. While alcohol consumption has been a thorny road safety problem for decades, opioid use has become a major cause of accidents only recently. In 1993, drivers under the influence of opiates were involved in only about 2% of deadly car accidents. By 2016, that figure had more than tripled to over 7%.

The results of the study have been criticized by doctors and pain management experts who point to research showing that individuals who take prescription opioids develop a tolerance for the drugs and can operate motor vehicles safely. They say the accidents studied were more likely caused by individuals abusing rather than using medical opioids. Critics of the study also say that the kind of injuries people take drugs like hydrocodone and oxycodone to treat can also impair the ability to control a motor vehicle.

Toxicology tests are generally only performed on drivers when signs of intoxication are obvious or the injuries suffered in car accidents are severe. When representing clients who have been involved in less serious crashes, attorneys with experience in motor vehicle accidents who suspect that drug impairment may have played a role could use subpoenas to obtain the medical records of the driver responsible. While simply being prescribed narcotic medications would not be enough to establish impairment in a criminal court, it could help attorneys to meet the less strict standard of proof in a civil lawsuit.