The Matakana link road is being built primarily to cater for future urban development, rather than to reduce current traffic congestion, according to a report released to Mahurangi Matters under the Official Information Act.
The 2014 Matakana Link Project Feasibility Report sheds some light on why the proposed route does not connect directly to the Puhoi to Warkworth motorway northern interchange.
Up until now, the reason for locating the intersection halfway between Hill Street and the motorway interchange has been unclear.
However, the New Zealand Transport Agency report shows that the link road is being built to serve future urban development, with any reduction in traffic congestion being a secondary consideration.
The area, which is currently undeveloped, is expected to eventually accommodate 1500 residential lots.
The report analysed six route options for connecting the road to the current state highway.
One option, supported by many in the community, was to connect directly to the new motorway interchange, but this option was dismissed.
The report states that with the preferred route, traffic from a future western collector road will use the link road to travel to Matakana. But if the link road is connected to the motorway, traffic on the western collector will opt to use the already congested Hill Street intersection instead.
The motorway interchange roundabout has been designed to have three arms and would require a fourth to accommodate a link road connection. This would involve extra earthworks and 200-metres more road.
The report estimated that based on 2014 industry standards, building the link road and connecting it to the motorway would cost $22.8 million (exc. land and gst costs), compared to $10 million for the preferred option.
Meanwhile, a preferred option for the Sandspit link road was also identified in the report. Once again, this was chosen primarily to cater for future development.
The report states that the chosen option, which connects to Sandspit Road near the existing lime works road, is too far south for most motorists. However, it was chosen because other options bordered a quarry and would not have provided efficient access to new development.
The feasibility report also shows that the Matakana link road was first envisaged as a two-lane road, with provision for two more lanes to be built to meet future growth requirements.
It says that cycling and walking infrastructure is also a key requirement when constructing the road.