The Illawarra has a higher rate of driving under the influence of drugs than Sydney, a new report reveals.
The Centre for Road Safety report also shows that, across the state, the rate of positive drug-driving tests is now much higher than those for random breath testing.
The report, released this week, compiled the number of fatalities and crashes involving a driver with either cannabis, speed or ecstasy in their system.
In the study period from January 2010 to December 31, 2013, there were 14 fatal crashes and 238 driving offences involving drugs in the Illawarra, compared with 34 deaths and 1978 offences in Sydney.
But a different picture emerges after the report factors in populations.
The drug offence rate per 10,000 licensed drivers in the Illawarra is 7.9, compared with the Sydney rate of 6.4.
The report said that since police began conducting roadside testing for cannabis, speed and ecstasy across the state, an average of "about one driver in 50" tests positive.
For alcohol, the rate is one in 241 drivers.
Roads Minister Duncan Gay said the report showed, for the first time, the effect of drug-driving on the state's roads.
"For the first time in this state's history we have undertaken research that allows us to uncover that a disturbing 11 per cent of road fatalities involved a driver or motorcyclist who had illicit drugs in their system," Mr Gay said.
"We know that in the last four years, at least 166 people died on our roads in crashes involving motorists with at least one of three illicit drugs, cannabis, speed or ecstasy in their system.
"We will be stepping up the fight to remove this behaviour from our roads and help save the lives of innocent motorists endangered by the idiotic actions of drug-drivers."
Police Minister Stuart Ayres said the number of roadside positives for drug-driving was likely to increase, as the police were using new and more powerful detection equipment.
"The machine has more sensitive detection thresholds and will reduce the proportion of drivers who are screened as negative at the roadside," Mr Ayres said.
He said education was the key in reducing the incidence of people driving under the influence.