A police officer had "no chance" of avoiding a collision with a 16-year-old youth as he walked along a Far North road after dark because the headlights on his patrol car were on low beam, an Independent Police Conduct Authority (IPCA) investigation has found.

Rawiri Wilson died after a patrol car driven by Constable Jamie Anderson struck him from behind on State Highway 1, near Ohaeawai, 11km northeast of Kaikohe, on July 25, 2009.

Mr Wilson was walking on the road with his cousin Gideon Porter, 16, who was injured in the crash, about 11.45pm.

Mr Anderson should have been driving with his lights on high beam. With the headlights on low beam, he had no chance of avoiding a collision with the boys once they came into view, the IPCA found.

The police crash investigation indicated Mr Anderson could only have seen the boys when he was 22 metres away. If travelling at 80km/h, he would have covered that distance in approximately a second.

The evidence indicated Mr Anderson was braking the police car when it struck Mr Wilson.

Using his mobile phone while driving, and driving with headlights on low beam, were not unlawful, but these were not the actions of a reasonable and prudent driver, the IPCA said.

Mr Anderson had been using his personal mobile phone while driving on duty. It had not been established whether Mr Anderson he used his mobile phone at the time of the collision or in the seconds before it.

He admitted sending text messages while driving on police business "whenever I feel like it".

The IPCA agreed with the finding of Coroner Garry Evans that Mr Anderson was texting as he drove out of Ohaeawai.

In July 2009 it was not against the law to use a mobile phone while driving. At the time, the use of mobile phones while driving was being widely debated and was actively discouraged by various government agencies, including police.

Mr Anderson would have been aware of an incoming text message on his mobile phone 20 to 30 seconds before the crash. He said that he did not open his phone or read the text message and the IPCA accepted that the available evidence did not establish he was using it immediately prior to impact.

The night was described by witnesses as "pitch black". There were no street lights and both boys were wearing dark clothing.

The pair had been drinking and had smoked cannabis some five hours earlier.

The IPCA found that because the pair were under the influence of alcohol and cannabis, they were not paying attention to the risk or exercising caution as they walked on an unlit section of State Highway 1.

There was no suggestion that Mr Anderson had consumed any alcohol, but he should have been breath tested "without delay" at the scene of the collision. Due to the relative remoteness of this incident, all available police resources were focused on dealing with the victims and crash scene, so Mr Anderson was not breath tested until two hours after the crash.

Mr Evans, in inquest findings released in May, said if Anderson had used high beam, the fatal accident "might have been avoided".

He recommended that the New Zealand Transport Agency look into whether the Land Transport (Road User) Rule should contain requirements in relation to safe walking by pedestrians on state highways.

It should also address when and in what circumstances drivers must drive with a vehicle's headlamps on full beam, he said.

Anderson will not face criminal charges, and is still working for the police.

The authority made no further recommendations.

- Rachel Pinder, NZPA