A major tightening of road safety legislation, including measures to take blood samples from drivers injured in crashes, came into force today.
New roadside impairment testing for drugs has also been introduced.
The measures see the closure of a loophole that allowed drunken drivers involved in serious accidents to avoid blood tests through being unconscious or by claiming injury.
Under the new rules, medical authorities may now take a sample from a driver who is unable to provide consent to the procedure.
A driver will be asked on regaining capacity whether they consent to the issuing of a certificate of the test results based on the sample.
The certificate stating the level of alcohol in the bloodstream may be used in a subsequent prosecution.
If the driver refuses to allow the sample to be used, the refusal will be an offence and penalties can include disqualification from driving.
Gardaí have also been given additional powers to allow for roadside impairment testing for drugs.
Drivers can now be asked to perform a range of balance and co-ordination movements, which may indicate if they have been driving while under the influence of drugs.
The measures were announced today by Minister for Transport, Tourism and Sport Paschal Donohoe, Road Safety Authority Chairperson Liz O'Donnell and An Garda Síochána.
Meanwhile, the PSNI has said that some drivers stopped on the roads last Christmas were so drunk they could barely stand up.
A total of 258 people were caught drink driving in Northern Ireland over the Christmas period, with the PSNI warning they will be conducting more operations this year.
Assistant Chief Constable Alan Todd said this figure was particularly disappointing, adding that "it just beggars belief that some people still insist on attempting to drive after drinking."
The PSNI have announced plans to coordinate road safety operations across border counties with gardaí.
Of the 258 people detected drink driving between the end of last November and the 2 January this year the youngest was 15 and the oldest was 78, with more than three times as many men caught as women.