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James Cook Dr / Discovery Dr intersection upgrade

James Cook Drive/Discovery Drive intersection upgrade

Share your thoughts on plans to upgrade a key Whitby intersection

**Please note we have cancelled the public drop-in sessions

Consultation open 23 March 2020 - 17 April 2020

The intersection of James Cook Drive and Discovery Drive is being upgraded in preparation for the opening of Transmission Gully and the associated Whitby link road.

We’d love your feedback on two proposed options, which we are consulting on until 17 April 2020.

Based on preliminary assessments, there are two upgrade options for this intersection:

  • a roundabout (the preferred option), and
  • a T intersection, with change of give way priority.

The intention is to future proof this intersection, so it can handle the expected increase in traffic following the opening of Transmission Gully plus future development growth around Whitby.  It will need to provide safe access for vehicles, cyclists and pedestrians, while managing travel times effectively.

NZTA modelling estimates that 5000 vehicles are expected to use the intersection daily once Transmission Gully opens, up from around 4500 vehicles currently.  Further modelling by Porirua City Council, suggests that by 2031 the number of vehicles using the intersection each day could rise to 6000.

The intersection is on an important busy arterial and public transport route.  Just two non-injury crashes have been reported at or near the intersection in the past 10 years.

**The use of traffic lights was investigated and not considered an option due to lower than optimal traffic volumes that would result in off-peak delays for all users.  They are also extremely expensive to construct and maintain, well above the other intersection options.

Option 1 – Roundabout (preferred option)

Following the opening of Transmission Gully and the Whitby link road, traffic modelling has projected that a roundabout will operate well during the morning peak period with only minor delays during the evening peak period

Looking forward to 2031 it is projected that a roundabout will operate well during peak periods with only minor delays expected on the James Cook Drive southern approach during the evening peak period.


  • Balances traffic flows evenly on all approaches during peak periods.
  • Reduces vehicle speeds
  • Safer pedestrian crossing facilities can be introduced
  • Performance beyond 2031 is acceptable
  • Safer for cyclists


  • Cost to implement is likely to be between $250,000 and $300,000

View the plans

Option 2 – T intersection with change of give way priority

Following the opening of Transmission Gully and the Whitby link road, traffic modelling has projected that a T intersection will continue to operate well during peak periods

Looking forward to 2031 it is projected that the intersection will generally operate well during peak periods, however significant delays are expected on the Discovery Drive approach during the evening peak period.


  • Traffic flow along James Cook Drive would be improved as this is expected to become the dominant traffic route
  • Relatively low cost to implement at approximately $100,000.


  • Does little to improve intersection safety with limited controls available to reduce traffic speed.
  • Pedestrian safety would remain compromised
  • Performance beyond 2031 is expected to decline and introduce significant delays on the Discovery Drive approach.

View the plans

How to have your say

We welcome your feedback on the options to improve this intersection.

While we are on alert Level 4 and in isolation to help eliminate Covid-19, the best way to provide your feedback is to fill in the form below and:

  • scan the form and email it to Traffic & Road Safety Engineer Luke Benner 

  • email your feedback directly to Luke Benner at the above email address

  • or post it to Porirua City Council, PO Box 50218, Porirua 5240.

Please share your feedback by 17 April 2020. Thanks

Next steps

  • Consultation closes 17 April
  • Collate feedback
  • Refine a preferred option
  • Communicate preferred proposal to submitters and wider community
  • Seek Council approvals (June/July 2020)
  • Project put out for tender and construction (July/December 2020)


If you have any questions, please contact Porirua City Council Customer Liaison Manager (Transport) Claire Giblin