New transport rules covering the operation of agricultural vehicles on roads will take effect from June.
The rules establish a two tier system for those vehicles based on a 40 km/h speed limit.
Those operating below that speed will be exempt from warrant of fitness and work time requirements.
The changes follow a review of laws covering more than 40,000 registered agricultural vehicles after complaints from farmers and rural contractors about their inflexibility.
The Ministry of Transport estimates the changes will result in benefits of more than $50 million over 25 years without compromising road safety.
Agricultural vehicles registered from when the law takes effect will have to use a flashing amber warning beacon when they're travelling on roads.