Police are working to plug about 1.2km of radio blackspots along Transmission Gully before the road opens.
Photo: RNZ / Dom Thomas
A police spokesperson said two additional radio sites would be required and it wanted portable radio coverage in higher risk areas.
"As Transmission Gully is flanked by hills, there are significant portions of the highway that are not adequately covered by police's existing radio sites.
"Police are actively engaged with Waka Kotahi who are aware of police and other emergency services' coverage short falls and we are currently exploring funding assistance and site selection options. All parties are working to prioritise and ensure the radio coverage is addressed before the road opens for both the safety of the public and emergency services."
The coverage was required along two stretches of road, one being 500m long and the other 700m.
There was also between 3km and 5km of road where there was no cellphone coverage, although this did not mean emergency calls would not get through.
Waka Kotahi infrastructure delivery national manager Andrew Thackwray said all providers rerouted 111 calls to any available mobile network and the sections without mobile coverage varied by the different providers.
The operator of Transmission Gully, Ventia, would also have full comms capability along the full length with their radio network.
"The new motorway's radar system will detect incidents anywhere along the motorway and is monitored 24/7 by an operations team who will direct incident response assistance to stopped vehicles, for example.
"For incident response Ventia will have full communication capability along the new motorway using their radio network, and will be present at incidents to support for emergency services as required."
Thackwray said the police radio repeater would be in place before the road opened and Waka Kotahi was discussing the possible future provision of coverage along Transmission Gully with mobile network operators.
"This would involve the installation of additional cellular towers. These discussions will continue to be progressed once construction of the new motorway through Transmission Gully is complete."