Homebush Bay Dr and Underwood Rd / Australia Ave upgrade

[Henry Ung]

Hey all,

The Australian and NSW Governments have invested $100 million into the upgrade and removal of the Homebush Bay Dr / Australia Ave / Underwood Rd roundabout.

https://roads-waterways.transport.nsw.gov.au/projects/homebush-bay-drive-australia-ave-upgrade/index.html

The preferred plan is to convert it into NSW's first diverging diamond intersection.

It's interesting to see that this was thought of for this intersection.

What ruins the efficient flow of traffic is the southbound HBD off-ramp to southbound HBD on-ramp movement to connect to the DFO.

Henry

[Aevion]

Interesting. I was wondering how long it would be before the other states decided to start using these setups. Looking at the diagram it appears that this will be a pretty well-flowing interchange, but then I'm not personally familiar with this interchange and the amounts of traffic that use it. By RMS' descriptions though, it appears that it's quite the black spot. Looking on Street View, it also seems like there's really no great way to get into that DFO is there? In a more ideal situation I'd suggest a bridge across from Wentworth Road directly into the complex, but it seems that that area has been purposely traffic calmed and closed off.

My own experience with these interchanges is limited to Caloundra Road at this stage, which I found to be a very smooth-flowing interchange even in peak traffic (in fact, that whole upgrade project is a thing of beauty, apart from the iffy signage). Strathpine Road isn't quite completed yet, but from what I've seen so far it's a very small band-aid fix. Unfortunately it's in a pretty narrow corridor though, and that stretch from there to the Gateway doesn't seem to have been touched at all since it was built 46 years ago.

[Vincent]

I've driven through this intersection a few times. The DFO entries are poorly designed, and I think what adds to the issue is that this is a fast roundabout with relatively poor visibility. It's designed in such a way that you can travel through it (too) quickly, and because of the poor design of the entries, people get confused about which lane they need to be in. Cars can disappear quite easily behind the infrastructure holding up HBD as well, and with the speed of the roundabout, cars which have disappeared behind pillars/ramps can come at you quite quickly. You're then in a situation where people who visit the DFOs infrequently are unfamiliar with the layout, and they're contending with regulars who do know what they're doing. 

The diverging diamond interchange sounds like an interesting notion. From what I've seen, implementations in Queensland seem to have gone quite well. Wasn't there one being constructed at Varsity Lakes as well?

Cheers,

Vincent.

 

[Aevion]

There certainly is one at Bermuda Street, which appears to have been opened to traffic in April (I wasn't aware of that fact until now, but I haven't been following this project much). Can't find any decent photos of it yet, so I'll reserve judgement for when the full M1 upgrade is completed, as I don't believe the interchange is fully operational yet.

Back to Homebush Bay Drive, I'm shocked the DFO development was approved in such a location, especially with those accesses. Was there a ton of traffic using the roundabout before DFO was opened?

[Vincent]

I'd have to defer to more seasoned bods, because the HBD overpass and DFO have been where they are for as long as I've had a reason to drive through there (about 10 years), and traffic has always been consistently heavy on that stretch.

Looking at historic aerial imagery of the site, it looks like it was just a roundabout up until about 1997 - Sam puts the opening of the overpass at February 1998 on Ozroads. I'm not sure how long the DFO has been there for, but the previous structure is in pre-HBD imagery from 1985. My guess is that when they built the DFO, they used the existing infrastructure for ingress/egress without much thought as to future traffic flow. Lack of foresight? In Sydney? Quelle surprise.

Cheers,

Vincent.

[Sam L]

DFO opened in 2001, which would probably have been welcomed by a State Government wondering how to keep the Sydney Olympic Park area activated post-Olympics. At the time there wasn't a lot of resi/office land use in SOP and that growth has increased traffic over the years. 

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From: aussie-...@googlegroups.com <aussie-...@googlegroups.com> on behalf of Vincent <vincent....@gmail.com>
Sent: Friday, 24 June 2022 11:38 AM
To: Aussie Highways <aussie-...@googlegroups.com>
Subject: [Aussie Highways] Re: Homebush Bay Dr and Underwood Rd / Australia Ave upgrade

 

[davis]

It did some duty as a building trades showroom / bulk goods before its current incarnation as a factory outlet / bulk goods centre.

[Sam L]

Media release today with additional funding (now $150M) for upgrade of this intersection. I thought they had settled on a diverging diamond but this indicates maybe not?

https://minister.infrastructure.gov.au/c-king/media-release/50-million-boost-homebush-bay-drive

"The project will deliver a signalised intersection, with a number of options set to be put to community consultation in the coming months." 

[AlienChex]

First Falcon Street, now DFO… NSW remains diverging-diamond-less yet again

Bets on the Picton Road / M31 intersection also being changed? It’s the only other planned DDI iirc 

[Peter Freeman]

Has the Falcon Street design been changed, at this late hour?

[Sam L]

Yep, the diverging diamond was dropped in 2023
https://media.caapp.com.au/00vh37.pdf

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Subject: Re: [Aussie Highways] Re: Homebush Bay Dr and Underwood Rd / Australia Ave upgrade

 

[Peter Freeman]

Wow, I'm 2 years behind the times!

I can't deny that I'm disappointed. I wanted these early implementations to shine the light for wider use. However, I'm not going to argue the point - I can see both sides of what is in the link from Sam. It's still a great project, and I retain optimism that, one day, Beaches Link will be resurrected.

Peter.

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Subject: Re: [Aussie Highways] Re: Homebush Bay Dr and Underwood Rd / Australia Ave upgrade

[Paul Rands]

I suppose the questions are, do they really make a difference or are they just a gimmick or something that increases crashes due to the unusual nature of them?

Paul R

li...@paulrands.com

http://www.expressway.net.au/

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[Peter Freeman]

USA DDI experience (where there are now around 80) is very firmly positive, for both standard-diamond upgrades and new builds.

[Hubert Lam]

https://www.smh.com.au/national/nsw/200m-fix-for-sydney-s-worst-roundabout-to-start-in-2027-20251202-p5nk1p.html

Diverging diamond Interchange no longer an option. 

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[Nihat]

Disappointing given the success as mentioned above. If people follow the rules it's easy to navigate. They are sticking with it for the Picton Rd/Hume Motorway interchange 

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[AlienChex]

Main feedback was that drivers would find it too confusing. Given Sydney drivers, yeah people would absolutely mess up and get in the wrong lane. 

[Sam L]

From the Preferred Option Consultation Report:

Given that there are currently no operational examples of this intersection type in Sydney, concerns were raised about the design’s intricate traffic crossover configuration and the adequacy of clearance times for vehicles passing through 17 Transport for NSW the intersection and crossovers. A significant portion of feedback called for the consideration of a more traditional signalised intersection design. 

 Following the COVID-19 pandemic, updated traffic modelling also revealed changes in traffic conditions and projections that would better support a more traditional signalised intersection design. 

Further investigations carried out after the public display of the preferred option also identified budgetary and physical project constraints, prompting a reassessment of the proposed design and creating an opportunity to explore alternative options. In addition, the decision to investigate alternative options was also influenced by feedback from Sydney Olympic Park Authority and Strathfield Council, who both expressed a desire to minimise impacts on key features and assets within the adjacent Bicentennial and Bressington Parks. 

 Transport re-evaluated the preferred option (DDI) as well as additional alternative DDI and more traditional signalised intersection options in an extensive Options Assessment Process. 

Following this process two options were shortlisted and proceeded to further detailed assessment. The two shortlisted options were a modified DDI and a more traditional signalised intersection option, configured as a SPI. A SPI intersection is designed to efficiently manage high volumes of traffic in limited space and is commonly used in urban environments where space is constrained. 

 Both options were compared in a Multi Criteria Analysis workshop held in September 2024. After further optioneering consideration a new preferred option arranged as a more traditional signalised intersection was endorsed for progression to concept design. 

 The revised design will: 

 • provide a high benefit solution to congestion and safety at the Homebush Bay Drive and Australia Avenue intersection for all road users 

 • reduce impacts to utilities within the project footprint 

 • reserve existing movements through the intersection, except U-turns 

 • include a separated U-turn Bay from the northbound lane off ramp to the southbound on ramp 

 • reduce impacts to community reserves owned by Sydney Olympic Park Authority and Strathfield Council, including Bicentennial Park and Bressington Park.

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