Consultation closed 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.
Thanks to everyone who gave us feedback on the proposed upgrade options.
We received 18 submissions:
Detailed design work for Option 1 - The Roundabout will now go ahead, incorporating the feedback received from residents, and the results of a recently completed safety audit. These plans will be used to seek Council approvals and to enable costings to be developed in preparation for tendering and finally construction.
The intention of this work is to future proof the 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 suggests that by 2031 the number of vehicles using the intersection each day could rise to 6000.
Just two non-injury crashes have been reported at or near the intersection in the past 10 years
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. Early cost estimates for this project were between $250,000 and $300,000
Please find below answers to common questions that were asked by residents in feedback.
Q. What are the forecasted traffic volumes using the intersection during morning and evening peak periods?
A. Following the projected opening of Transmission Gully and the associated Whitby Link Road in 2021, it is estimated that around 500 vehicles will travel through the James Cook Drive/Discovery Drive intersection during the AM and PM peak hour periods. This number is projected to increase to 600 by 2031.These peak hour vehicles volumes represent 10% of the daily traffic volumes projected to be using the intersection in the future.
Q. Is it possible to introduce two lane approaches as part of the roundabout design to improve traffic flow at busy times?
A. Intersection modelling demonstrates that a roundabout with single lane approaches will operate well and continue to do so to beyond 2031. It is crucial that the risk of crashes occurring at the intersection is reduced. This is achieved by encouraging reduced speeds on approach to the roundabout through a variety of design techniques. The introduction of two lane approaches makes it much harder to reduce speeds through design and does little to improve safety. It is also not warranted as vehicle delay and associated congestion are projected to be manageable with the existing proposed layout well into the future.
Q. What consideration has been given to cyclists and pedestrians using the intersection?
A. As covered briefly above, a key driver in upgrading this intersection is to better manage and improve safety for all road users. This will be achieved through a design that keeps speeds below 30km/h at the roundabout. This will reduce the risk for cyclists and allow them to share the road more safely with vehicle traffic. We will also look at using road markings to indicate to drivers that cyclists may be present at the intersection. The option for a bypass for cyclists will also be investigated. Crossing points for pedestrians will be provided on all approaches at a safe distance away from the roundabout. These crossings will feature central refuge islands and hold rails to allow pedestrians to cross the road in two goes, which is particularly important for the mobility impaired and elderly.
Q. How will the side roads along James Cook Drive & Discovery Drive be affected following the intersection upgrade and the opening of Transmission Gully?
A. It is anticipated that reducing vehicle speeds and balancing traffic flows at the roundabout will provide sufficient gaps in traffic flow to allow vehicles on the side roads to safely join the main traffic flow. The roundabout will be instrumental in improving traffic flows through the intersection, as it stands currently.
If you have any questions, please contact Porirua City Council Customer Liaison Manager (Transport) Claire Giblin firstname.lastname@example.org
Find out more about this project to improve traffic flows along Kenepuru Drive and surrounding streets, plus read the latest updates on our dedicated Kenepuru Corridor webpage
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Our road network covers 295 kilometres of sealed roads, 23 bridges, five footbridges, almost 400 kilometres of kerb and channel, four kilometres of culverts, 44,500 traffic signs, three sets of traffic signals and 14 car parking lots.
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Porirua is experiencing and planning for additional considerable growth. Annual residential growth is over twice the historical average, and there are major investments in the region such as the Eastern Porirua Regeneration Project, Porirua Adventure Park, Kenepuru Landing, Plimmerton Farms etc.
This growth, and the completion of major projects such as Transmission Gully will increase the pressure on our roading and transport network.
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Download the NZTA / Porirua City Council Procurement Strategy for Roading and Transport activities