He stressed the decision to give a written warning, rather than a fine or prosecution, is "not letting someone off".
"This is for minor offences and about education. The whole reasoning is to change their behaviour. If somebody doesn't want to offend again, that's all well and good. If they do, a record of previous warnings are on the system and they're unlikely to get another warning," said Mr Searle.
"It's not a let-off. For many people, being stopped by a police officer and given a written warning will be enough."
Careless driving, failing to keep left, unsafe lane changes and failing to give way are among the offences eligible for a warning.
Any offences which could be punished by imprisonment are not. These include drink-driving or drug-driving, reckless or dangerous driving, driving while disqualified, or boy racing.
"All the road policing staff have these devices to do it electronically. Put in the details, print out the warning, ticket issued on the spot."
But minor offences would not automatically be given a written warning, said Mr Searle, but rather left to the discretion of the police officer.
Any decision relating to a crash accident must be referred to a supervisor and drivers could be warned more than once. "It's up to the discretion of the officer. I'd be surprised if someone got a second warning for the same offence in a short space of time."
The most common offence in an earlier trial in Wellington last year was careless driving.
Mr Searle said the new give way rules came into consideration for the timing of the pilot and may be an "appropriate option" for when the rules were broken.
The written traffic warnings are the next stage in the police alternative resolutions programme and come after the pre-charge warnings, to replace prosecutions of minor criminal offences.
Nearly 14,000 pre-charge warnings were given last year, each saving one hour of police officer time and a case diverted from the courts.
Last year there was a nationwide 8 per cent reduction in minor cases being dealt with in court.
ON NOTICE
* Possible written warning:
* Careless driving
* Failing to keep left
* Unsafe changing of lanes
* Failing to give way
* Operating a moving vehicle with insecure load
No warning:
* Drink-driving and drug-driving
* Reckless or dangerous driving
* Careless driving causing injury or death
* Racing, exhibition of speed and sustained loss of traction offences (boy racer offences)
* Driving while disqualified, suspended, revoked or contrary to limited licence.