The National Highway Transportation Safety Administration has revealed that the number of fatal traffic incidents in which drugs were found to be present in the driver's system has increased over the past four years.

In 2005, 15,363 drivers fatally injured during a traffic incident were tested for the presence of narcotics, depressants, stimulants, hallucinogens, cannibinoids, PCP, anabolic steroids and inhalants. Of those drivers, 3,710 were found to have at least one of the drugs in their system, though NHTSA is quick to remind us that the simple presence of the substance does not indicate whether or not the driver was under the influence at the time of the accident.

In 2009, of the 13,801 drivers tested, 3,952 tested positive for drugs. That's an increase of 242 drivers, though NHTSA says that the figures could be misleading. There's a sizable discrepancy between how states test and report the presence of drugs in fatal traffic accidents, and that discrepancy could push the results higher or lower in a sizable way. You can check out the full PDF report here.

[Source: NHTSA | Image: Victoria Hazou/AFP/Getty]