"While I'm thrilled that the ban on using cellphones while driving is finally being instated, I think the problem is far worse than people seem to realise,"Associate Prof Liz Franz said.
Transport Safety Minister Harry Duynhoven announced this week that a doubling in the number of car crashes involving cellphones had led the Government to consider a ban on drivers using the devices.
The use of personal digital assistants such as a Blackberry would also be banned under the proposal.
But drivers would still be able to use hands-free devices.
The rule did not go far enough, Prof Franz said. Concentrating on conversation and the nature of the conversation, rather than the physical act of holding a cellphone, was what distracted drivers.
Research showed people had a limited ability to pay attention to two or more different things at once, and when they had to their responses became increasingly delayed, she said.
Drivers' brains were already overtaxed with everything going on around them and freeing up their hands was going to make little difference.
"It is ridiculous. It's like saying if we had three arms it would still be OK to use the cellphone. It is an incomplete view and it is misleading."
There was no doubt using a cellphone while driving increased the risked of crashing, but from a policy point of view it was still a very small part of the whole issue, she said.
Respondents to an Otago Daily Times online poll overwhelmingly supported the ban. Results showed 85% of 158 voters agreed cellphone use should be banned while driving.
"Just yesterday I watched a young woman blithely drive through a red light in central Dunedin with eyes down, apparently texting.
"I'm sure she still doesn't know about the red light and, to make matters worse, there was a toddler in a child-seat beside her," one contributor said.
Southern road policing manager Inspector Andrew Burns said cellphone use had contributed to 94 crashes in the southern police district, including two deaths, between 2003 and 2007.
Cellphones were a major distraction and while not the total solution, banning their use was an excellent start to reducing driver distraction, he said.
Many distractions made people poorer drivers.
At present, the only thing drivers were banned from doing behind the wheel was watching television.
However, if police believed a distraction, for example, putting makeup on, texting or drinking behind the wheel, was causing a driver to drive in a careless manner, they could be given a ticket and/or charged.
Mr Duynhoven said the plan would be accompanied by an education campaign.
Cellphone use while driving is banned in 45 countries.
