Gazetted in 1999,[1] it is a generally quicker route to get between Auckland and New Plymouth as well as connecting to the Waitomo Caves, just south of the SH 39 southern terminus.

Following Kakaramea Road, the highway passed through Ngāhinapōuri then the township of Pirongia.

SH 39 is classified as an 'arterial' highway under the One Network Road Classification.

As the expressway is a faster route, SH 39 was diverted away from Ngāruawāhia to its current terminus at Te Rapa.

[12] The road runs close to the Waipā River for most of its length.