Transport Minister Andrew Constance said the speed camera signs will go over the next 12 months.

"This is about changing culture and changing behaviour," he said on Thursday.

"We've seen it happen with our world-leading mobile phone detection program, where the rate of people offending has steadily declined.

"No warning signs mean you can be caught anywhere, anytime and we want that same culture around mobile speed cameras," he said.

Last year, 136 people in NSW lost their lives and 2941 were injured due to speeding motorists.

This year, 275 people have been killed on NSW roads compared to 314 at the same time last year.

Mr Constance said tougher penalties for drink and drug-drivers would apply from next year.

"Research shows you are 23 times more likely to crash if you are under the influence of both alcohol and drugs - this massive, life-threatening risk needs a stronger penalty," he said.

Modelling from Monash University Accident Research Centre showed the move could save between 34 and 43 lives, and prevent around 600 serious injuries in NSW each year.

"These tougher penalties send the message that this behaviour won't be tolerated," Mr Constance said.

Since 2015, 101 serious crashes involved a driver or rider with illegal levels of both alcohol and drugs in their systems. These crashes killed 98 people and seriously injured another 52.

Revenue raised from the mobile speed camera program will go directly to road safety initiatives.

Labor's John Graham accused the government of scrapping the warning signs in a bid to raise revenue.

"It's a budget measure. We know that fine revenue will leap by about a third as a result of this single measure," he told ABC radio.

Australian Associated Press