The New Zealand Transport Agency (NZTA) is slated to test weather-activated speed signs on State Highway 29 over the Kaimai Range in the North Island of the country next week.

Starting today, the trial is undertaken to prepare for an innovative new trial aimed at reducing crashes, and will be accompanied by placing of new signs showing various speed limits such as 60km or 80km on the highway.

The testing will be carried out between the bottom of the Waikato side of the Kaimai Range and the power station at Ruahihi, until 22 October.

"The new signs will allow us to drop the speeds to 60km/h on the Waikato side and 80km/h on the Bay of Plenty in adverse weather."

During the Kaimai Range weather-activated speed sign trial, which begins in November, 22 variable speed signs will be installed on a 12km stretch of SH29 between the State Highway 28 (SH28) junction on the Waikato side, and Soldiers Road on the Tauranga side.

The variable speed signs, along with four web cameras, will be linked to a weather station at the summit of the Kaimai Range. The posted speed will be reduced during adverse weather conditions.

NZTA chief safety advisor Colin Brodie said the two-year trial aims to encourage people to drive at safe speeds when rain, ice and fog hit the Kaimai Range.

Brodie said: "Our data shows that over 70% of the crashes on the Kaimai Range happen in wet weather, and that over 40% of these were caused by drivers travelling too fast for the conditions.

"Despite the changeable weather on the Kaimai Range, people still attempt to travel at 100km/h.

"The new signs will allow us to drop the speeds to 60km/h on the Waikato side and 80km/h on the Bay of Plenty in adverse weather."

The road signs are also expected to be used during roadworks or in the event of a crash when speeds may be reduced to as low as 30km/h.