The new motorway connects with the existing SH1 (Johnsonville–Porirua motorway) at Linden.
When travelling north, motorists can either use the left or centre lane to continue on SH1 via Transmission Gully, or the centre or right lane to continue on the ‘old SH1’ – renamed and signed as SH59. Motorists travelling to Porirua City Centre or Plimmerton, should use their usual route – such as the off-ramp at Mungavin Avenue. Motorists travelling to Whitby, Waitangirua, SH58, or Kāpiti should use the new motorway.
Motorists travelling south on Transmission Gully will merge with southbound traffic on SH59 at Linden. The merging lanes here resemble the configuration at the bottom of Ngauranga where SH1 and Sh2 come together and the two ‘centre lanes’ gradually become one.
Waka Kotahi is working to prepare the wider State Highway network for the opening of Transmission Gully. This includes measures such as variable messaging signs (VMS) and additional CCTV cameras for traffic monitoring to improve the efficiency and safety of the merge point between Transmission Gully and the old SH1.