A new survey has revealed that seven out of ten drivers in Washington, US, have used marijuana and almost half of those have recently driven within a couple of hours after marijuana use.

The preliminary results of a June survey, which measures driver impairment on Washington’s roads, found that nearly 90% of those same drivers said they did not think marijuana degraded their driving ability.

In the survey, 25% of those respondents felt that driving while high made them a better driver.

Washington Traffic Safety Commission director Darrin Grondel said: "It’s extremely troubling to me that so many marijuana users think that driving high is not a problem. It’s a serious problem."

"It’s extremely troubling to me that so many marijuana users think that driving high is not a problem."

More than 1,000 people died in impaired driving collisions in Washington from 2009 through 2013.

Impaired driving is said to be involved in nearly half of all traffic deaths and more than 20% of serious injury collisions. Extra DUI patrols are teaming up and coming up with high penalties to overcome this problem.

A DUI arrest carries up to a year in jail, a $5,000 fine, as well as a loss of a driver’s license.

DUI offenders can also be ordered to wear electronic ankle bracelet and install an ignition interlock device, which prevents a car from starting if the driver has been drinking.

The Whitman, Pend Oreille and Ferry County Sheriff’s Offices and the Washington State Patrol will team up with Spokane, Whitman, Pend Oreille and Ferry Counties, the Cheney, City of Airway Heights, Colfax, Eastern Washington University, Pullman, Republic and Washington State University Police Departments to participate in the extra patrols, with the support of the Spokane County Target Zero Task Force.

All the extra patrols are said to be part of Target Zero, which strives to end traffic deaths and serious injuries in Washington by 2030.