It’s probably not a surprise that marijuana use is being found more often among drivers who are involved in fatal accidents.

Following voters’ legalization of recreational marijuana in 2012 and the opening of the first retail cannabis shops last summer, that increase in use appears to have found its way onto our roads.

Data from the Washington State Traffic Safety Commission shows a 48 percent increase in fatal accidents in which drivers tested positive for marijuana use. Statewide, of 429 fatal accidents in 2014, causing 462 deaths, 207 involved drivers who were impaired by alcohol, drugs or both and 86 involved drivers who tested positive for marijuana. For the year previous, of 401 fatal accidents and 436 deaths there were again 207 impaired drivers, and 58 drivers tested positive for marijuana. Prior to 2013 that number fluctuated but had not seen an increase similar to that shown in 2014.

A few points need to be made about the safety commission’s numbers: Testing positive doesn’t distinguish between active and inactive THC in the blood, meaning the driver may or may not have been impaired by marijuana use at the time of the accident. And the numbers don’t break down those marijuana users who were or weren’t impaired by alcohol. Nor were there statistics available on drivers using marijuana who were involved in accidents that involved injuries.

While the marijuana use is concerning, driver impairment because of alcohol remains a much larger and deadlier problem. However, the numbers do reflect an increase last year in the number of people who are smoking marijuana and are then involved in fatal accidents.

It’s an expected result of legalizing marijuana, but it’s not an acceptable one.

Efforts to combat drunken driving, including tougher penalties and public education campaigns have shown success. Again the numbers bear that out. The number of fatal accidents caused by drunken drivers statewide declined from a high of 169 in 2009 to 102 last year. In the first three months of this year, there were 17 fatal accidents involving drunken drivers.

What has worked to fight drunken driving should also work to dissuade driving under marijuana’s effects. The penalties for driving under the influence are the same whether its alcohol, marijuana or any another drug. The state, since 2012 has said drivers are impaired if they have a blood level of .05 nanograms or greater of THC.

Public campaigns already are underway. The National Highway Traffic Safety Administration and the Ad Council draw the comparison directly with their “Buzzed Driving is Drunk Driving” campaign and ask drivers to sign a pledge on their website.

Just as they are when using alcohol, personal responsibility and some self-knowledge are the best tools for those who use marijuana. According to a NHTSA fact sheet, the effects of cannabis are felt within a few minutes and reach their peak within 10 to 30 minutes. The high from marijuana can last about two hours, but its effects on alertness and reaction time — the skills a driver relies on — don’t return to baseline levels for three to five hours. And using alcohol in combination with marijuana increases the level of impairment.

Washington voters made the choice to equate marijuana with alcohol as a substance that adults should legally be able to enjoy. But it was with the understanding that we would do so responsibly.