Thirty-five motorists have been arrested since 1 December as part of Wiltshire Police's Christmas anti drink-drive campaign.
More than 1,700 roadside tests have been carried out with 31 drivers arrested for providing a positive test and four failing to provide a sample.
Wiltshire Police said extra resources had been put in to the campaign.
"For motorists who fail to heed those warnings... you will be caught," the force spokesman said.
"We are putting a great deal of time and effort into our activity, which is shown by the numbers of tests conducted so far.
"The aim of the campaign is to highlight the grave dangers to all road users and anti-social aspect of drink and drug driving.
"I am pleased that so far the messages seem to be getting through as the percentage of those failing tests is lower than last year, however we will not be complacent and road side checks and enforcement at the current levels will continue," he added.
During 2009 Wiltshire officers conducted 7,098 breath tests, 692 of which were positive.