Assistant Commissioner Road Policing Dave Cliff said overseas studies indicated that between 10 and 25 deaths, and hundreds of injuries, would be prevented if this change was made in New Zealand.
"Without exception, every jurisdiction showed significant reductions in alcohol-related trauma as a result of that move, so we would expect to see the same effect in New Zealand.
"The research says that when you reduce BAC level, the whole distribution of offending moves to the left, so high-end drinkers drink less, the risk declines across the whole population - that's the impact you see," Mr Cliff said.
Superintendent Carey Griffiths said many New Zealanders would be surprised by how liberal the drink-drive limit was.
He said for research, he had consumed 13 beers in two hours and was still below the 80mg limit.
"There's no way you would ever drive. It was an extraordinarily large amount of alcohol to be under the limit."
Mr Cliff said Waikato University research showed when people drank to the 50mg limit, many of them decided they were too intoxicated, did not drive and stopped drinking.
"By the time you get to [80mg], people are so affected by alcohol that they think they're okay to drive."
The police told MPs that a person who drove to the 50mg limit was six times more likely than a sober person to crash.
A person who consumed 80mg was 16.5 times more likely to crash.
Police pointed out that Sweden had a legal limit of 20mg per 100ml, and its road trauma rate was half of New Zealand's in terms of deaths per 100,000 people.
The Ministry of Transport was expected to release a report by the end of the year on how many injuries and deaths had been caused in the last two years by people who had a BAC level between 50mg and 80mg per 100ml of blood.
The average man who consumed two drinks was likely to have a BAC level of 20mg to 30mg, while the average woman who drank two drinks was likely to have a BAC level of 30mg to 40mg.
