Police are defending their efforts to persuade people not to drive when tired.
Two road safety campaign groups, the Candor Trust and Akilla, say public information campaigns are geared towards areas police can enforce, such as drink-driving and speed but ignore other factors.
However, acting national road policing manager Inspector Carey Griffiths says fatigue is one of the five fatal factors police are focusing on.
He says it can lead to crashes, although it is difficult to prove.
Land Transport New Zealand is due to spend more than $2 million on advertising targeting driver fatigue this year.
Mr Griffiths says that is four times the amount LTNZ will spend on seatbelt advertising.