Two of this weekend's fatal crashes involved tourists.
Assistant Commissioner of road policing Dave Cliff said police worked with ACC, the Ministry of Transport and the Transport Agency to tackle the issue, including encouraging rental companies to brief customers.
"There's an awful lot being done but I guess what it highlights is whatever you do you're relying on people obeying the rules and being vigilant," Mr Cliff said.
Kate Meldrum, general manager marketing and customer experience at Tourism Holdings, said tourists who used its campervans were given extensive information on the local road rules in their language before and during their trip. A sticker on the dashboard said keep left.
