Bringing in electronic detectors could double the number of people caught using their cellphones behind the wheel, according to research for the New Zealand Transport Agency.
The study by Opus Research looked at nearly 5000 drivers in Wellington, Porirua and Levin.
When the researchers used roadside observation they found about 5.5 percent of drivers appeared to be using their cellphones.
But when electronic monitors were used, that figure bumped up to nearly 10 percent.
Bringing in the hi-tech devices alongside the roadside observation that was already done could greatly increase the number of drivers caught out, the report said.
But it acknowledged the technology could not tell whether it was a driver or passenger using the phone - and if someone got a message or email but did not answer, it could still show up as cellphone use.
Researcher Joel Burton said the detectors were not sophisticated enough to be used by the police - but, if the technology was developed, it could help catch drivers using their phones.
The police were considering the report.