Police said they are pleased after none of the 600 motorists they stopped failed a breath test for driving under the influence of alcohol or drugs.
Durham Police carried out a roadside screening operation earlier this week as part of an ongoing campaign.
Over three hours, 602 motorists were stopped and asked to take a voluntary breath test to see if they were driving with alcohol or drugs in their system.
Police said all of the tests were negative.
Acting Ch Insp Ken Cook said: "This was a concerted effort by our staff to ensure that motorists are abiding by the legislation.
"The overall aim is to reduce the number of casualties on our roads and I am heartened by the fact that every single one of the tests carried out was negative."