Trying to stay under the limit may not be enough to stay safe on the roads.

Hospitality New Zealand has released new guidelines encouraging people to know their alcohol limits and stick to them.

It says the average woman should stay under two drinks in two hours, and the average man should stay under three drinks in two hours to be within the legal blood alcohol limit for driving.

But Police National Road Policing Manager Superintendent Steve Grealy said the message is misleading.

"It's very, very difficult, if not impossible - to determine what a standard drink is in our country. It differs from establishment to establishment, and it differs between individuals."

Hospitality New Zealand has criticised the hard line Police have taken against drink driving, but Grealy said any amount of alcohol is too much.

"Changing a conversation from drink and drive to drink or drive - in our view, those are two completely distinct acts that should never be put together."