An expert says we should consider other options than dropping speed limits to reduce crashes.

An NZTA estimate suggests only five-percent of open roads should have their 100-kilometre an hour limit.

New Zealand Initiative research fellow Dr Patrick Carvalho told Heather du Plessis-Allan road quality should also be taken into consideration.

"Let's have in mind only two per cent of state built highway network is actually made up of dual carriage roads."

He says that this is one of the main reason why we have such a high number of crashes compared to the rest of the world.

He notes that Switzerland has speed limits of around 120 kilometres an hour, but have wider roads. 

Carvalho agrees that reducing speed limits would lower the road toll, but other factors should be considered. 

He does not dismiss the data, but says that some of the methodology should be questioned. 

"It doesn't take into account the economic costs of reducing speed limits."

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