A New Zealand first weather-activated speed sign system will be trialled on a high-risk stretch of State Highway 29 through the Kaimai Ranges.

NZ Transport Agency today announced the two-year trial has been in the works for the last few months and will begin later this year.

Variable speed signs will be located on a 12km stretch of the Kaimai Ranges showing enforcable lower speeds during bad weather.

Map showing the location of the electronic speed signs on a high risk stretch of road.

NZTA will monitor the weather station at the summit and in times of adverse weather, fog, heavy rain and ice it will activate up to 22 electronic speed signs that will be set up between SH29 and Soldiers Road on the Tauranga side and the SH28 junction on the Waikato side. The signs will typically reduce the speed from 100km/h to 80km/h at Soldiers Rd and 60km/h at the junction.

However, the signs will have the ability to show a range of speeds from 30km/h to 100km/h in extreme weather, or events such as road crashes or road works.

The speed limits will be actively enforced by police and are aimed at reducing the number of crashes along the 12 kilometre stretch.

According to NZTA data 70 per cent of crashes on the Kaimai Ranges occur in wet weather, with 40 per cent of these caused by drivers travelling too fast for the conditions.

'Despite the changeable weather conditions a significant number of road users still attempt to travel at 100km/h,” reports NZTA.

The latest fatality to occur on the Kaimai Ranges was on Saturday when Matamata teen Jasmine Clothier was killed in a two car crash on the winding stretch of the ranges in wet weather. Read more about that here.

Earlier this year Katikati girl Jasnoor Kaur, 9, was killed in a head-on crash near the summit of the Kaimai Ranges.

The 55-year-old Mount Maunganui driver of the Nissan that crossed the centreline colliding with the blue Subaru Jasnoor was a rear seat passenger in also died following the crash.

NZTA reports SH29 is a high volume national strategic route and its safety, efficiency and reliability is important to the economy. Approximately 9000 vehicles travel over the range daily, including around 1300 heavy vehicles.

The trial will begin later this year and is the first project of its type in NZ.

'The aim is to see whether safe and appropriate speeds can be achieved with drivers altering their driving behaviour in adverse weather conditions. If the trial is successful it may be rolled out across other similar sites in New Zealand,” says NZTA in a statement.

Advanced messaging will give drivers notice and variable speed signs will be visibly active and enforced.