Drivers using phones are four times more likely to cause a crash as other drivers, research shows.
Rotorua Coroner Wallace Bain made the observation in his findings into the death of Paula Jessep, 37, who died on December 22, 2011 in a head-on collision between her Toyota Rav 4, which she was driving and a Nissan Sunny on State Highway 1, north of Tirau.
Ms Jessep was alone and the Nissan held three women, all of whom were injured in the crash.
Ms Jessep was driving to Hamilton from Rotorua and although it was raining heavily at the time of the crash, police suspected she had been texting on her cellphone as she drove.
Dr Bain found Ms Jessep died from severe head and other injuries as a result of the crash and has talked about the dangers of using a cellphone while driving.
Dr Bain has recommended his findings be forwarded to the Minister of Transport to support and increase a public education campaign in respect of the dangers of driving while distracted which included the use of cellphones, texting and general tiredness.
During the inquest Senior Sergeant Fane Troy said when he arrived at the scene of the crash, he examined Ms Jessep's cellphone, found sitting in the driver's footwell of her car. Mr Troy counted a total of 19 texts sent by Ms Jessep, the last of which was sent about 15 minutes before the crash.
During the inquest Ms Jessep's son Elliott, who was a student in Hamilton, said since the crash he had been speaking out about the texting and driving and commented on the "text can wait" campaign being run by the women in the other vehicle.
Elliott had declined to join the campaign and although he thought a good job was being done, he did not want to join it because it put his mother in a bad light.
He spoke of being concerned about how the heater was set high in his mother's car and felt that if she was driving in a hot car it would make her a lot more tired and distracted.
He pointed out that it cannot be said that at the moment of the crash when she drifted across the road that she was in fact texting - reading one coming in or sending one out. Elliott agreed there was a strong inference that in fact she was doing this at the time of the crash.
Dr Bain commended the women for their campaign and said he agreed with Ms Jessep's son Elliott, who gave evidence during the inquest, that distracted driving was a real threat to people on the roads.
In the first 21 months of the ban on the use of handheld cellphones while driving more than 14,000 tickets were issued.
Figures provided by the police showed 28 people died on New Zealand roads in crashes caused by people using cellphones since 2007. Dr Bain said figures released under the Official Information Act showed that in the year to March 2012, 149 crashes were thought to have been at least partly caused by mobile phone use.
"There is no doubt on studies conducted and from basic commonsense that texting while driving impairs drivers' abilities."