Twenty-one drivers in Nelson have been handed roadside suspensions after being stopped at police checkpoints over the holidays.
Police said more than 8000 drivers were stopped at checkpoints testing for alcohol and drug impairment last weekend.
Ten people will appear in Nelson District Court charged with driving with excess breath alcohol, each facing a minimum six-month disqualification and a fine.
A further 11 drivers were fined $200 and received 50 demerit points.
In a statement, police urged motorists to stay safe over summer by following the road rules - staying within the speed limit, wearing seatbelts, driving sober, and being alert at all times.
They said alcohol and drugs were a contributing factor in about 20 percent of all fatal crashes.
"January is one of our highest risk months on the roads as so many people are still on holiday; travelling around visiting loved ones and making the most of their time off over the summer.
"Officers are also frustrated with an increase in people speeding, with several drivers in recent days receiving roadside suspensions and facing court action."