Research published today has found that a quarter of all drivers in Northern Ireland still admit to driving over the speed limit.
However, a spokesperson for Department of Environment said the annual Road Safety Monitor Survey showed a general improvement in road users' attitudes and behaviour.
Road Safety Spokesman
"We cannot ignore that some hardcore irresponsible attitudes still exist in Northern Ireland," said Harry Green, road safety spokesman for the Department of Environment.
While it was encouraging that the numbers who said they travelled at the appropriate speed was growing, he said, it was still a shock that so many flouted the law and ignored their responsibilities to other road users.
"That is despite the well known fact that excessive or inappropriate speed is the single biggest cause of death and serious injury on the roads," said Mr Green.
In 2004 inappropriate speed was the cause of 31 deaths and 219 serious injuries on Northern ireland roads and unfortunately those statistics showed the effect of the "irresponsible minority".
Driver fatigue has been identified as a growing road safety issue in the result of three consecutive safety surveys.
Mr Green said almost half of drivers admitted to feeling drowsy when driving, something the DOE was very concerned about.