Frequently Asked Questions

The Department for Infrastructure and Transport (the Department) is upgrading Happy Valley Drive / Chandlers Hill Road intersection and Happy Valley Drive / Windebanks Road junction.

Happy Valley Drive (north of Chandlers Hill Road) and Chandlers Hill Road are under the care and control of the Department for Infrastructure and Transport. Happy Valley Drive (south of Chandlers Hill Road) and Windebanks Road are under the care and control of the City of Onkaparinga.

In late 2022, we held stakeholder meetings, two community drop-in sessions and an online survey, in addition to feedback that was received through the Department’s engagement phone line, emails and web-form submissions. The online survey for the community was undertaken from 21 November 2022 and 9 December 2022 and we received 266 project submissions.

In April 2024, we consulted with the community on the proposed concept design to improve the intersections. We held two community drop-in sessions, an online survey and key stakeholder meetings, in addition to feedback that was received through the Department’s engagement phone line, emails and web-form submissions.

We received 655 pieces of feedback throughout the consultation period. Key themes of the feedback included concerns relating to queuing, delays, access and motorist and pedestrian safety. Overall, the project was supported by the community, however there were concerns raised about the proposed impact to the significant river red gum tree opposite the Happy Valley Drive / Windebanks Road junction.

Following this, an updated concept design was developed to take into consideration feedback received during the 2024 consultation. Funding was announced in 2026 for the delivery of the intersections upgrades. Community engagement took place on 30 July and 1 August 2026, offering an opportunity for community to view the updated design, meet the project team, offer local insights and ask any questions.

Through the 2024 consultation, local community raised concerns about the proposed impact to the significant river red gum opposite the Happy Valley Drive / Windebanks Road junction. As a result of the feedback received, we reviewed the geometry of the roundabout and shifted the roundabout to the northeast to avoid impacting the tree.

Additionally, based on feedback received we have updated the design to avoid impacting the Happy Valley Reservoir Reserve woodland, relocated the emergency access gate and realigned the boundary loop trail.

Key considerations in development of the proposed concept design included:

• environment and heritage impacts including landmark trees
• impact on local access
• traffic movements and future traffic considerations
• social impacts
• existing infrastructure such as water, wastewater, communications and power utilities
• reducing the need for land acquisition
• pedestrian and cyclist movements
• available funding

Traffic signals were considered in the early planning phase for this project. Traffic signal options have a bigger impact in terms of land acquisition and vegetation, achieve relatively similar performance to the roundabout options and are significantly more expensive than other options. Community feedback also supported the roundabout concept design option for both intersections.

Traffic modelling has confirmed that a single lane roundabout at the Happy Valley Drive and Windebanks Road junction is sufficient to manage future traffic volumes in the area.✖

As above, the planned single lane Windebanks roundabout has been determined sufficient to manage future traffic volumes. The approach distance between Chandlers Hill Road and Windebanks Road provides an adequate distance to safely and effectively merge in the approach to the Windebanks roundabout. Two northbound lanes would not allow for this safe merge.

A dedicated left turn lane is provided for traffic turning left from Chandlers Hill Road onto Happy Valley Drive (northbound) so a bypass lane is not required from a traffic performance (capacity) perspective.

A left turn bypass lane would require a crossing of pedestrian and cyclists, creating an unsafe interface with motor vehicles. Furthermore, providing a bypass lane would attract further land requirements for road widening and costs to deliver.

Traffic modelling considered current volumes and analysis of predicted growth in the area.

It was undertaken to understand how the proposed upgrades will perform and influence travel time through the intersections.

Consideration is always given to limit the removal of vegetation along project corridors as much as possible, however for a large upgrade such as this, some vegetation will be impacted. Feedback received from the community during 2024 consultation highlighted the importance of reducing potential impacts to significant trees.

We have worked to protect the significant river red gum, which will no longer be impacted by the design. The Department will continue to work to minimise impacts to vegetation wherever possible.

Site surveys and investigations will continue until late 2026. Early works, including services activities, are expected to begin in early 2027.

More information about construction timeframes will be provide in the new year.

We encourage you to subscribe to receive future email updates via the project website.