The *555 service was introduced in 1991 to let cellphone users alert the Traffic Safety Service (TSS) to road hazards, breakdowns and problems with driver behaviour.
Police fielded 250,697 calls on the line last year alone.
Bay of Plenty road policing manager Kevin Taylor said the *555 line was "invaluable".
Most of the calls were about speeding, followed by careless and dangerous driving.
A smaller number of complaints came in about unrestrained children, drivers talking on cell phones and cars going through stop signs.
Vehicles travelling too slowly and carrying animals in a way that "wasn't quite right" were other causes for concern, he said.
"In the Bay of Plenty we take a proactive approach. So the attitude is, if somebody has seen something significant enough to prompt them to call us - and we've asked them to be our eyes and ears - it's incumbent upon us to act on it.
"As a direct result of members of the public phoning in, [we've] prevented serious crashes from occurring."
Giving drivers the opportunity to inform on one another helped deter dangerous behaviour on the roads, Mr Taylor said.
At the time *555 was brought in, New Zealand had only 65,000 cell phone users.
The number of cell phones in use jumped to 4 million by 2006.
Calls range from traffic congestion to faulty traffic signals, drunk drivers, insecure loads and surface flooding.
Police communications operations manager Inspector Mal Schwartfeger said *555 calls were lower urgency than 111 calls.
"[*555] is a handy, short dial system for members of the public to report non urgent issues of concern about New Zealand roads and members of the public that drive on them who put other road users at risk."
Police can use the tipoffs to intervene, and have the power to prosecute if a witness is willing to make a statement. Fines can be issued on the spot if the driver admits the offence.
New Zealand Transport Agency (NZTA) road safety director Ernst Zollner said too many Kiwi families had their holidays marred by avoidable road tragedies.
"Drivers can do their part by planning ahead to share the driving and avoid fatigue, being patient and keeping to safe speeds, driving sober, avoiding distractions and checking their tyres, indicators and lights before heading off."
Summer was also a popular time for kids to learn how to cycle, he said.
"The two most important things you can do as a driver to help avoid summer cycling tragedies are to slow down and to keep your focus on driving, take your foot off the gas pedal and avoid distractions, turn the cell phone off and put it out of reach."
Nationally, the 2012/13 Christmas holiday period saw six deaths, 70 serious injuries and 283 minor injuries - compared with 19 deaths the previous summer.
The official holiday period runs from 4pm on Christmas Eve until 6am on January 3.
The highest Christmas holiday road toll on record was in 1972/73 when 37 people died.
The most commonly cited contributing factors for holiday crashes include losing control, travelling too fast for conditions, alcohol, inexperience and fatigue.