Auckland Traffic Chaos

Yesterday, Saturday December 6th 2014, we had a little crash on the Auckland Harbour Bridge which resulted in 3 of the northbound traffic lanes being closed. This being being at around mid-day in the build-up to Christmas and the harbour bridge being one of the main pieces of transport infrastructure in Auckland resulted in a complete grid-lock for large parts of the central city and the motorway network.

NZHerald - 2014

So of course the question comes up, "Does Auckland need a better road network?"

Well it just so happens that this is one of the critical points on the Auckland motorway network that NZTA has known about for some time and hence they have been developing alternative plans for.

The first thing that NZTA has been doing is building the Western Ring Route (WRR) which is a complete alternative to SH1 through Auckland. If yesterdays crash happened in an Auckland where the WRR was complete we would have seen far less people being disrupted. We still would have seen congestion in much of the inner parts of Auckland as the WRR really does only provide for those going through Auckland or are living on the outer edges of the city.

The other project NZTA has in the works which is more directly related to this would have been the Additional Waitemata Harbour Crossing (AWHC). This project looks to replace the existing harbour bridges function as SH1 through auckland and leave the existing bridge to provide for local movements between the northshore and the city.

If we look closer at the AWHC it would have helped in 2 ways. Firstly the AWHC would be designed to a much higher standard in terms of road geometry and therefore it would be much less likely that the crash would have occurred at all. Secondly, had the crash occurred, either on the bridge or in the new tunnel, it would have left the other connection open and at full capacity.

Neither of the above 2 projects would result in there being zero impact, obviously when you loose 3 of the 4 northbound lanes on the only connection between the Northshore and the city you will get disruption. However, if these two projects were complete and we had this crash most of the city would not have even known or cared.

Moments like these we tend to get the various armchair experts coming out and expressing their opinion on what would fix the issue with one obvious call for better public transport. So one call we get is that if we had the Congestion Free Network (CFN) people would have been able to simply leave their cars at home and take the bus or the train to where they wanted to be. This of course misses the point, creating another isolated system doesn't create any redundancy or resilience but rather creates another layer where the same issue can happen again.

We actually see this currently with the existing motorway and rail networks.
When we have an issue on the motorway the motorway suffers and the rail network is fine.
When we have an issue on the rail network the rail network suffers and the motorway is fine.
In effect, the more layers you apply the greater the chance of having a failure, however the cost of that failure would be less as your usage would be more diverse.

So if we look at the rail side of things, one of the down sides of the Central Rail Link (CRL) is that we make our entire rail network dependant on the CRL being operational, all we will need is one breakdown or signal fault in the CRL and the entire rail network will need to stop, we have a similar issue with the electrification of the network.

So in terms of yesterdays event what would have it been like had we had the CFN? Well unfortunately with this being a weekend the likely result would have been very similar to what we saw, large amounts of congestion. The simple reason for this is that the types of trips people make in the weekend just aren't suited for public transport, of course some of them are however the majority aren't and this is why we see PT volumes taking a dive in the weekend whereas road volumes tend to carry on similar to that of a week day.

Traffic Volumes - Part 2

To carry on from my previous post, I'm going to look at how the currently proposed crossing could operate in terms of capacity and diversity. For this I will again be using the values from the 2010 study located in the Transport and Traffic Model Report.

For a quick summary, the predicted demand across the harbour are as follows:

2008 = 168,150 vpd

2026 = 197,830 vpd

2041 = 205,200 vpd

Traffic Modelling

For a quick note on how these volumes are arrived at:

These volumes come from a regional traffic model that takes into account a large number of assumptions such as land use changes and public transport. The model is not all that detailed on specific elements, such as does this left turn have a pedestrian crossing, but takes a look at the big picture and the general capacity and demand on a system and so on a macro scale is very detailed. When new capacity is added to the model, such as a new harbour crossing, not only will the traffic distribution change but so does the demand due to the potential for trips being increased.

So using the 2010 Study we can see how the travel over the harbour changes with the increase in capacity. Note that these values are the expected AADT and not the demand, even with the new crossing there are still plenty of constraints on the system in other locations and so we will still have demand in excess of capacity.

2008 = Existing Bridge = 168,510

2026 = Existing Bridge = 95,590

2026 = New Crossing = 134,100

2026 = Total = 229,690 (16% more demand)

2026 = Existing Bridge = 110,070

2026 = New Crossing = 144,240

2026 = Total = 254,310 (23% more demand)

Induced Demand

As you can see, the new crossing has enabled a large number of increased trips over the harbour, 23% or 49,110 more each and every day. Comparing demand and actual volumes we can see that the repressed demand, or demand that can't be provided for, is reduced from 18% to 13% which is a sizeable change.

So what you have seen here is induced demand; in the existing situation the shortage in capacity results in trips not occurring, when the capacity is increased the congestion is reduced which in turn enables the repressed trips from before to come out and join the system which in turn increases capacity. 

In a way you can think about it like the apple display at the fruit store. When the display is full of nice juicy apples everyone who thinks about getting an apple will likely grab one. Once the display starts to get low and only the less desirable apples are left people will think twice and maybe decide they don't want an apple. Eventually you will run out of apples and no matter how desperate someone is to get one they simply can't.

In a large city the transport system is very similar to this fruit stand as it's simply not practicable or financially feasible to provide a system that can provide ideal conditions for everything and everyone all hours of the day. So when you put a few more apples in the bowl or upgrade a road the large number of people who have been held back will quickly take up the new supply.

This brings us into a bit of a debate about how much road capacity should be provided. Although road travel by private car can be very convenient and pleasant, when it comes to large volumes of commuters significant dis-benefits arise making it less ideal. In my view, this is where we need to think about what we do with the existing bridge if a new crossing is built.

New Crossing

With the new crossing we get the following peak hour traffic volumes:

2026 = 5,300 (actual), 6,260 (demand)

2041 = 5,300 (actual), 6,440 (demand)

Capacity = 3 x 1800 = 5,400

Existing Bridge With New Crossing

Next we will look at how much traffic will be using the existing bridge after a new crossing has been built.

2026 = 5,430 (actual), 6,390 (demand)
2041 = 5,800 (actual), 6,320 (demand)

From Appendix G of the 2010 Study the existing bridge has been modelled with 5 general traffic lanes, 3 in the peak direction and 2 in the counter peak direction. 1 of the existing lanes is handed over for active modes and another 2 given to buses.

What isn't clear here is how these lanes are arranged, and so it's hard to know what the capacity of each route actually is therefore I wont comment further on the arrangement in the report.

Future Layout

In terms of the bridge layout I'm going to refer to what could happen which continues on from my Victoria Park post. For this, the idea is to reduce the footprint of the existing motorway through St Marys Bay so that more of it can become open public space as seen below.

Turenscape.com

In this layout I propose to make the existing bridge 2 lanes each way for general traffic with this traffic using two existing clip-ons. The central span would then be converted to provide a single lane in each direction for buses and freight with something like the Skypath being added for active modes.

This would end up being very similar to what is currently proposed for the Pakuranga to Botany Busway and would extend along Fanshawe St into the CBD. 

Auckland Transport - 2014

So how does this work traffic wise?

Well when using the clip-ons the lanes are nice and wide so we can expect full utilisation.

2 x 1,800 = 3,600 vehicles per hour (vph)

Compare this to the current 3 median lanes during peak hour where the shy-line effect reduces the capacity of the lanes.

3 x 1,440 = 4,320 vph

Those 3 lanes are including freight however, if we assume a low number of 5% given most freight will be taking the new crossing we have 4,104 vph.

What you will notice here is that in my proposal we have 12% less capacity for general traffic over the harbour. The question to be asked here is; is this what we want?

If we refer back to the network layout we see that the existing bridge provides for people travelling to or from the north into the CBD and Ponsoby. From my perspective we don't really want large volumes of people driving to these destinations, neither of them have much scope to handle any additional vehicle demand but would greatly benefit from improved PT and less private vehicle traffic. To this extent I'm not really too worried about there being less vehicle capacity over the existing bridge and through St Marys Bay when you look at the benefits that come through doing so.

NZTA - 2010

Summary:

So when we look at what a new crossing could mean for traffic volumes and people moving over the harbour we get given a few questions and options. Certainly the new tunnel provides for those long distance trips that are not wanting to go into the CBD itself but what do we do with the existing bridge. We have the option here to downsize the private vehicle demand and turn some of the road space over to open public space, or we can leave the roadway as is and let people chose how they travel to the CBD.

If we refer back to the traffic modelling, the tested scheme results in 23% more demand on people wanting to travel over the harbour using both the tunnel and the existing bridge due to the improved access. Of that 23% however, how many more do we want driving to the CBD?

AWHC - Traffic Volumes

To continue my series on the Additional Waitemata Harbour Crossing (AWHC) I'm going to have a look at the traffic volumes and potential lane configurations such a project could bring.

Project Layout

Based on the 2010 study I am going to assume that the the project will consist of two 3-lane tunnels which will take over the function of SH1. These tunnel will run directly from the Central Motorway Junction (CMJ) through to Northcote Point. For additional details you can view the 2010 study drawings here.

Auckland Council - 2014

One of the interesting aspects of the current designs for the AWHC is that the cross harbour traffic flows are split to provide for two separate functions. The new tunnel provides for north/south movement through the city and bypasses the CBD with users wanting to go to the CBD and Ponsonby taking the existing harbour bridge. The big benefit of this is that traffic travelling long distances on the motorway network are not forced to mix with commuters making short trips over the harbour to the CBD.

The following image comes from the 2010 study showing the routes each crossing provides for.

NZTA - 2010

Anyone familiar with Auckland will know that the existing bridge is rather large with 8 lanes in total with a movable median barrier enabling the bridge to operate in a 3/5 configuration to provide for the tidal peak flow. 

Stuff - 2011

With the new crossing in place we no longer need this level of capacity provided over the existing bridge and so we are presented with an opportunity to reassign the space on the bridge to serve different priorities.

Traffic Volumes

In terms of traffic volumes I am going to use the 2010 studies volumes.

The important thing to note when looking at the AWHC is that we currently have two crossing, the existing Auckland Harbour Bridge (SH1) and the Upper Harbour Bridge (SH18)

As a base line we get the following volumes:
Annual Average Daily Traffic

2008 (AADT)
SH1 = 168,150
SH18 = 27,160
Total = 195,000

2026 (AADT)
SH1 = 197,830
SH18 = 78,260
Total = 276,000

2041 (AADT)
SH1 = 205,200
SH18 = 80,500
Total = 286,000

What's not shown above but is in the report is that a large part of this growth is expected to come from increased inter-peak volumes. Currently inter-peak traffic is about 60 to 70% of the peak hour traffic flow, this is expected to increase to 80% in 2026 and 90% in 2041 meaning you can expect peak hour conditions for pretty much most of the day.

Something else that isn't shown in the above is the demand; if you're a commuter you will likely have experienced driving on a congested road and there have likely been occasions where you have taken a different route or mode in order to avoid the congestion.

Taking the existing harbour bridge as an example, the morning peak in 2008 experienced 7,640 vehicles per hour (vph) in the southbound direction, however the demand for this link is 18% more than this at 8,980 vph. So from that we have 1,340 vph that are either taking a different route, not making the trip or have changed to another mode.

Capacity

If you're someone that lives on the Northshore and commutes over the bridge in the morning you will likely know that the bridge itself seems to flow somewhat smoothly. The following numbers list the capacity of the roads that feed onto the bridge and then the bridges capacity, as you will note the connections to the bridge act as constraints leaving some residual capacity on the bridge. 

Northern Motorway 3 x 1800 = 5,400
Esmonde Road 6s Signal Time = 1,200
Onewa Road Signal Intersection = 1,000

Total Inflow = 7,600

Bridge Capacity = 5 x 1800 = 9,000

One thing I haven't taken into account above is the affect of thee narrow lanes on the bridge. Currently the clip-on lanes are 3.5m in width which is fine for 1,800 vph however the lanes on the central span are just under 3.0m in width and this reduces their capacity by 20% to 1,440 vph. This reduction in lane capacity comes from something called the "shy-line" effect. Most people who drive over the bridge will know that tight feeling of travelling in the central lanes and the "shy-line" effect is the technical term used; this has the impact of people driving slower, increasing vehicle spacing and shying away from objects such as barriers which then impacts the next lane over.

For some technical reading on "Shy-Lines" Section 6.2.1 of the SHGDM gives a few details.

If we reduce the capacity of the central 3 lanes to 1,440 vph we get a total capacity over the bridge of 7,920 vph, this lines up quite well with the 2008 volume of 7,640 vph crossing the bridge which suggests that only a small increase in traffic volumes would result in flow breakdown and congestion on the bridge.

Conclusion

So in conclusion we have:

• Current traffic volumes put the peak hour near capacity
• The existing connections hold back traffic to prevent the bridge from getting over capacity
• The existing crossing is unable to provide for the current demand with 18% of trips being lost or diverted.

Given this post is getting somewhat long I'll leave talking about the new crossing and how the volumes play over in the next post.

Cheers

AHWC - Victoria Park

Today's post is going to start a sub-series on what we can expect, hope or desire for if there was to be an Additional Waitemata Harbour Crossing (AWHC).

To start with a disclaimer; everything I'm about to say are simply my thoughts an ideas, the AWHC is still very early in it's design stages and so the actual form of the project is largely unknown at this stage. My thoughts are going to be based on the design drawings from October 2010.

For this particular post I am going to focus on the southern side of the proposed including Victoria Park, St Marys Bay and Freemans Bay. The image below shows the area in all it's glory back in 1959 just after the Auckland Harbour Bridge and Victoria Park Flyover were opened. For some history of the area, back in 1870 there was no Tank Farm and Victoria Park itself was a bay with what are the Victoria Park Markets today on the foreshore. 

Auckland Council - 1959

Jump 45 years into the future and things weren't all that different, St Marys Bay had been further reclaimed, a marina had been built and marine related light & heavy industry have been beavering away along with the petrochemical industry.

In the past 10 years there has been quite a notable change, with the successful redevelopment of the viaduct area and the growing CBD, the heavy industry has all been pushed out and the expensive process of decontamination and redevelopment of the Tank Farm has seen a rather large change to the area.

One thing that hasn't changed to much is the large viaduct that goes through the middle of the park. Now 55 years old this structure has been a feature in the park for pretty much half of it's existence. At first impressions you could point to it and call it a relic of the motorway age, the time when the focus was to get cars moving no matter the cost. Certainly when I went down there to take some photos I already had the opinion in my head that it would be a dark depressing environment with the noise of vehicles rumbling overhead.

Transport Logic - 2014

Transport Logic - 2014

Strangely however, once you're down there you can see that it actually serves another rather important function, that being a protected corridor from one side of the park to the other. Currently if you're an office worker at Wynyard Quater and want to go for lunch at the Victoria Park Markets on a wet day you can pretty much guarantee you will take this route under the flyover rather than staying out in the wet. Admittedly the northern end is rather average and turns into a carpark however this raises a question, how will we replace this facility when we remove the flyover?

Ironically, when I was down there most of the non-vehicle activity was right next to the motorway flyover, to one side the new skate park that was built as part of the Victoria Park Tunnel (VPT) was positively overflowing and on the other side there was a bunch of people playing rugby, all the while pedestrians and joggers were running under the bridge. Now I'm certainly not saying these people wouldn't be there if it wasn't for the flyover, it was more than I was rather impressed to see how negligible the impact of the structure was on the users of the park.

Something else I found rather interesting was the level of noise coming from the flyover, it's by no means whisper quiet but it was sort of hard to say which was worse out of the flyover or the local roads. For the flyover you hear the constant whoosh coming from vehicle tyres on the wearing course of the bridge, however for the local roads you hear the green light drag race every time one of the 5 sets of traffic signals changes. When I was down there it was a Sunday morning and traffic on the local roads was rather light, however I'd image that during the working week when there are notably more vehicles I'd say the local roads would put the flyover to shame in terms of noise production. One thing to note here is that the noise from the flyover could easily be greatly reduced, if the current steal handrails on the bridge were replaced with concrete barriers this would send most of the noise directly up into the atmosphere rather than laterally into the park.

Transport Logic - 2014

Transport Logic - 2014

One thing I think most people would agree on is that the park would look better if there were no bridge, the two images above give you the basic idea of what you can expect, one with the flyover and one without. This is where the AWHC comes in as part of the proposed project is to remove the flyover. Take note here that I am not saying that the only thing the AWHC does is remove the flyer, I'm just saying that this is one of the many parts of what would be a $2-3 Billion project.

The place where I see real potential for change however is through St Marys Bay. Currently we have one massive section of road, the reason why it is so wide is not just because we have large volumes of traffic moving through here but it's also the fact we have a number of on/off-ramps with quite complicated horizontal geometry.

Transport Logic - 2014

Now just imagine; if we are going to be removing about 60% of the traffic and sending it through an underground tunnel, and we also remove the various ramps connections that add to the current complexity we could put this section of road on quite a large diet which would free up a large amount of land right on our foreshore. The question is, what do we do with that land?

The following image is a before and after image in Boston which was done as part of "The Big Dig". Now that is the sort of change I would like to see along St Marys Bay, and in my mind well worth $2-3 Billion.

Turenscape.com

AWHC - What Should it Cost

This will be the first in a series of posts related to the Additional Waitemata Harbour Crossiing (AWHC), a new crossing of the main harbour in Auckland New Zealand linking the Northshore with the rest of Auckland.

In this post I am going to look into the cost of the project and compare it to recent projects built here in Auckland.

To set the ground work, based on the latest data the estimated cost of the project is $4.85 Billion. As seen here. We also have a rail tunnel only version estimated at $1.5 Billion.

When it comes to New Zealand and transport projects $4.85 Billion is a very large sum of money, to date the largest single transport project to go into construction has been the SH20 Waterview Connection valued at $1.4 Billion.

The AWHC comprises of the following aspects:

• two 3km long 3-lane tunnels (6km total)
• 2.8km of existing motorway upgrades and widening.

For details you can view some of the option drawings here

Now it just so happens that right here in Auckland we have been doing exactly this sort of work as part of the Western Ring Route (WRR) and so have some perfect price examples.

For the Waterview Connection, valued at $1.4 Billion, they are building:

• two 2.4km long 3-lane tunnels (4.8km total)
• 1.6km of 4-lane surface motorway
• 1 full systems interchange

For the SH16 Causeway Upgrade, valued at $220 million, they are widening and lifting the existing causeway over a 4km length, this would be largely similar to the sort of works required on the Northshore side of the AWHC where the existing motorway would need to be rearranged and widened.

Using the above rates, we get the following rough order costs:

• 3-lane tunnel = $580 million/km
• motorway widening and upgrading = $55 million/km

Based on those numbers if we were to go and build the AWHC today we would expect to cost in the range of $1.9 Billion.

So what is the reason for the rather large difference, well it all comes down to cost certainty. The AWHC estimate is a feasibility estimate that was done in 2010 and based on comparatively limited information with the intention of putting a value into the long term funding plan. The Waterview Connection was priced in 2011 and is now under construction based on very detailed information.

In a way it's very similar to getting a builder to price a house, if you give them very little information about where the house is, what size it is and what it is made of you will get a rather high price. However if you give the builder detailed plans and the schedule of quantities you will get a price much closer to what the actual cost will be.

Naturally my estimate is not 100% accurate either, but it is more an indication that the $4.85 Billion estimate is rather conservative. In reality we are more likely to see the actual cost be somewhere between the two and so I would say $3 Billion is more of a realistic value at this stage.

I hope you have enjoyed my first post putting some logic behind the cost of the AWHC.

For the next post, I'll look at just what we can get out of it.