According to Ministry of Transport statistics, distraction is a factor in about 10 per cent of fatal and serious injury crashes and cellphone use is a common cause of inattention.
Since the law was introduced the worst month in Northland was May last year when more than one driver per day was snapped - with 34 tickets dished out during the month.
Head of Northland traffic police Inspector Murray Hodson said research showed drivers using phones had slow reaction times, difficulty controlling speed and lane position, with those talking on phones four times more likely to be in a crash that caused injury. He said the number of tickets issued to drivers in the region was minuscule compared to the numbers actually seen talking on phones.
"From my own operational experience sometimes you can't stop someone safely when you see them on the phone.
"Many drivers simply choose to use their cellphone knowing it's illegal. They are blase towards the consequences if something goes wrong."
But he said text messaging was even more dangerous, with drivers completely taking their attention off the road.
"The good drivers who obey the laws do not deserve to be a victim of high-risk drivers using devices that distract them from driving."
AA general manager of motoring affairs Mike Noon said drivers were divided into two groups - those who obeyed the law, and those who supported the idea but took the risk thinking they wouldn't get caught.
Mr Noon said phone calls - even through a hands-free kit - should be kept to a minimum, especially in heavy traffic or poor weather.
Hands-free did not mean putting a cellphone on speaker-phone or throwing it on the dashboard. The penalty for driving while using a cellphone is an $80 fine and 20 demerit points.