Speed is the biggest killer on New Zealand's roads - with the number of deaths at a five-year high and motorcyclists the leading casualties.

An online survey of 1200 Kiwi drug users shows one in four drove after taking cannabis in the last year.

In a Drug Foundation survey of 1200 Kiwis, 24.5 per cent said they had driven after taking cannabis in the last year.

A new Super City transport agency will have responsibility for roading as well as buses, rail and ferries in the Auckland region.

Drivers will be banned from using cellphones in their vehicles from November under new rules that will also require motorcyclists to use their headlights during the day.