Some additional material was needed and excavated in Linden from the area that is now the northern of the Tawa College playing fields to the east of the motorway.

The first section of the motorway, running for three miles (5 km) from Johnsonville to Takapu Road at the southern edge of Tawa, was opened on Saturday 23 December 1950.

The northern end was located at the point where the Takapu Road northbound off-ramp and southbound on-ramp meet the present motorway.

With the completion of the second section, the northern end of the motorway was shifted to a point 500 metres south of Mungavin Avenue in Porirua.

At the time, there was a road intersection just north of this point connecting SH 1 to Kenepuru Drive with a level crossing over the railway line and bridge over the stream, and other accessways.

Construction of the Mungavin Avenue, Titahi Bay Road intersection in the 1960s enabled the connection of the Johnsonville–Porirua Motorway to the then new four-lane Porirua-Paremata expressway.

The work included building a two-lane flyover over the railway line and Porirua stream to connect Mungavin Avenue to the newly constructed four-lane Titahi Bay Road.

[6] The derelict and rusting structure was demolished with explosives by Territorial Army engineers on 15 December 1951.

However, the grassed medium bank between the north and south-bound lanes proved difficult and expensive to maintain, requiring lane closure to mow the grass, and the second section of the motorway and subsequent motorways were built on a single level.

After the establishment of Transit New Zealand in 1989 the use of green signage was extended to the entire state highway network to conform with Australian usage.

This reduced peak water flow and flood risk during heavy rain events.