Almost half of all drivers involved in serious collisions where people were injured were not tested by gardaí for drink or drugs according to a report issued by the Policing Authority.
The report is a compilation of responses by gardaí to the Authority on the issue of Roads Policing.
The Authority has described the figure as "troubling" and said it must be addressed as a matter of urgency.
There was a significant reduction in the number of roads deaths in 2017 and while this is to be welcomed, the Policing Authority said the numbers are still not in line with the targets set in the National Roads Safety Strategy (2013-2020.)
As part of its governance role it submitted a series of questions on roads policing in April of last year and said it is disappointed it took so long for the gardaí to respond.
A "most troubling aspect" the authority said is that 48% of drivers and motorcyclists were not tested at the scene of an injury collision from 2015-2017.
Among the reasons given were that no screening device was available and that a quarter of them had already been removed to hospital.
This the Authority said points to the ineffective deployment of equipment and a lack of agility at the scene of an accident.
The Authority is also not confident that a flexible evidence based deployment of resources is happening in practice and it wants evidence that the Garda fleet is being dynamically deployed
The commitment within the 2017 Policing Plan to increase Roads Policing Personnel by 10% was not achieved.
The Authority said it is frustrated at the lack of a costed training strategy and is critical of the lack of driver training for gardaí.
This results in new recruits emerging from the garda college in Templemore without any training to drive a Garda vehicle which results in garda stations having limited personnel that can drive a Garda vehicle in response mode, that is with lights and sirens.
The issue of data quality is another that extends beyond the area of Roads Policing and will persist as a theme of the Authority's oversight.
The Policing Authority said there needs to be a change in the Garda's organisational casual attitude to data.