The statistics were revealed on Monday, as the GNR launched a three-day international operation, named Tispol, designed to crack down on drivers who drive while under the influence of alcohol or drugs.
The campaign, a Europe-wide alcohol and drug enforcement initiative is co-ordinated by TISPOL, the European Traffic Police Network, represented in Portugal by the GNR, and involves officers conducting alcohol and drug checks at any time of the day and night.
Between Monday and Wednesday, GNR officers staged random checks on drivers and vehicles, on problematic stretches throughout the country where offences occur with some regularity, such as in the vicinity of popular nightclubs.
Since the beginning of the year, 3,860 drivers have been detained with criminally liable alcohol readings of or above 1.2 grams per litre of blood; around 505,000 drivers have been submitted to breathalyser tests since January, more than 9,300 of whom delivered positive readings, of above 0.5 grams/litre of blood, or 0.2g/l, in the case of drivers with a licence for less than three years.
The overall number of offences registered during the first five months of the year has dropped in comparison to the first five months of 2016, by nine percent (934 individual offences).
According to the GNR, four in every ten drivers caught drink-driving had a reading that was above 1.2 grams/litre, which is a crime. Altogether, the GNR states, up until 2 June 3,860 drivers had been arrested because of drink-driving.
Most recent figures, from 2015, show that 142 people were killed due to drink-driving, around three quarters of whom were drivers, 17 percent were pedestrians, and six percent were passengers.
Data available for this year, from the National Road Safety Authority, shows so far this year that 593 people have died on the country’s roads, with alcohol being a factor in around a quarter of the cases.
Last year a study published by the Portuguese Road Awareness bureau (PRP) concluded that driving under the effect of alcohol makes the risk of suffering a fatal accident 140 times greater.
Data on driving while under the influence of drugs is scarcer, with fewer offences registered, at around 100 cases per year.