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Let’s define “congestion” properly

An article in Toronto’s Globe and Mail newspaper just over a week ago, using the rather provocative title of “Sick of Congestion: build roads not transit” has unsurprisingly led to a lot of fisking of the information contained in the article – particularly around the different ways of defining congestion and how easily they can be misused. A good example of a response is this from Jarrett Walker.

Essentially, the argument put forward in the article is that when we look at cities around the USA (and internationally), at first glance the data appears to be showing that cities which have built a lot of freeways in the past few decades have lower levels of congestion than those which haven’t. Here are the key paragraphs:

This connection between road construction and congestion has been most comprehensively studied in the United States. There, 30 years ago, the Texas Transportation Institute at the Texas A&M University created an annual Travel Time Index (TTI) that estimates how much time traffic congestion adds to commuting by comparing actual travel times of commuters in different cities with the time it would take to travel the same distances in the absence of congestion.

Over the decades of its existence, the TTI has revealed some fascinating shifts. In the early days of the index, Phoenix, for example, had the 10th worse congestion among major urban areas in the U.S., despite being only 35th in population. It has more than doubled in size in the ensuing decades (it is now the 12th largest urban area in the U.S.), but its traffic congestion has fallen to 37th.

What explains this major improvement? A huge expansion of public transit? Hardly. Try a major road-building program. Something similar happened in Houston.

At the other end of the spectrum, Portland, Ore., has pursued road-skeptical policies similar to many major Canadian cities. The result is markedly worsened commuting times. According to the TTI, over the past 30 years Portland has gone from having the 47th worst congestion in the U.S. to the sixth worst.

Something in the next paragraph jumped out at me when first reading it – when mention was made of New Zealand cities as examples of those that had high congestion and hadn’t built many urban freeways.

Now data are starting to emerge that allow us to compare commute times among similar rich-world industrialized countries in Western Europe, the U.S., Canada, Australia and New Zealand. The results are not encouraging for the anti-car crowd. The worst urban congestion in this group of countries is in New Zealand, followed by Australia, countries that have invested relatively little in urban freeways.

If Auckland, with our gigantic spaghetti junction and motorways to just about every corner of the city, is an example of us not having invested much in ‘urban freeways’, I’d hate to see a place with lot of them – although Toronto’s Highway 405 (below) is pretty bad. I actually had a quick look at some figures from US cities with populations greater than 1 million people and from what I can tell based on some admittedly very rough calculations is that the size of motorway network would probably put us within top 10 US cities. Might have to look into that in more detail for a future post.

But the strange mention of New Zealand aside, the real issue with the article is its reliance upon congestion information from the Texas Transportation Institute that is decidedly dodgy in how it’s applied. Let’s pick up on Jarrett Walker’s criticism of the source data:

TTI believes that traffic congestion is a valid measure of people’s ability to access the resources of their city.  They do not measure actual travel times for all people, or the liberty and economic liberty that a good urban transporation system offers.  They apply these things as factors to a degree, but their bottom line is road congestion.

Specifically, their metric is the difference in travel times, by car, between travel time on congested roads and the same roads in a free-flow condition.   In other words, their baseline utopian condition is abundant free-flowing roads at all times of day.  (That condition is actually an economic impossibility in a city above a certain size with a healthy economy and no road pricing.)

Once you insist on measuring congestion, and against that fantasy baseline, you can get absolutely everything backwards…

… If you count everybody’s commuting time, Portland is ahead of most US metros.   … it is only congestion that is worse.  Yes, like all dense cities, Portland has exactly as much congestion as it makes room for, but it has low overall commute times, mostly because its carefully mixed density allows many people to commute very short distances.   Remember, if you are measuring car congestion, Portland’s transit riders and cyclists and the many people who can walk to work simply do not exist.  Crowley disses “congested” Vancouver for the same reason, even though Vancouver is the only Canadian metro where the long-term trend is toward shorter commute times, due to continued consolidation of housing and business around transit.

Jarrett sort of dances around the key point here while hinting at it in a number of ways. This key point is that for many people in the Portlands or Vancouvers of this world the level of basic congestion is irrelevant because they’re not affected by it. They’re walking, cycling, on a bus (as long as it’s in a bus lane or on a busway), a tram, a train or whatever. They’re not in the congestion.

This is the key point of the Congestion Free Network: it provides people with the ability to ‘opt out’ of congestion. This approach highlights that there are two elements to congestion:

  • How bad is the congestion? (Congestion intensity)
  • What proportion of people experience the congestion? (Congestion exposure)

It is the combination of these two elements which is what really matters – the actual effect of congestion can be increased or decreased not only through its intensity (which is all that the TTI measure, and arguably not that well either) but also through changing the proportion of people experiencing congestion. It seems that transport planners and particularly transport engineers focus so much on trying to reduce the intensity of congestion, even though this is nearly impossible due to induced demand, whereas the long-lasting way of reducing congestion is to provide ways to remove people from the congestion.

This means that a focus on cycleways, bus lanes, rapid transit and freight lanes (because it can be very important to shift goods around in a way that’s unaffected by congestion) are the true ways of reducing the actual effect of congestion. They’re also the only long-lasting ways of doing so. Todd Litman focuses on this distinction in his recent piece on Planetizen:

…the Texas Transportation Institute’s Travel Time Index, the INRIX Traffic Scorecard, and TomTom’s Traffic Index only measure congestion intensity, the degree that traffic declines during peak periods. Such indicators do not account for exposure, the amount that people must drive during peak periods and therefore their total congestion costs. Intensity indices are useful for short-term decisions, such as how best to cross town during rush hour, but are unsuited to strategic planning decisions that affect the quality of transport options or land use development patterns, and therefore the amount that people must drive. For planning purposes, the correct indicator is per capita congestion costs.

For example, a compact, transit-oriented city may have a 1.3 Travel Time Index (traffic speeds decline 30% during peak periods), 60% automobile commute mode share, and 6-mile average trip lengths, resulting in 34 average annual hours of delay per commuter; while a sprawled, automobile-dependent city has a 1.2 Travel Time Index, 90% automobile mode share, and 10-mile average trip lengths, resulting in a much higher 45 average annual hours of delay. Intensity indicators imply that the compact city has worse congestion due to greater peak period speed reductions, although its residents experience lower total congestion costs because they drive less during peak periods.

I talked about TomTom’s Traffic index here.

As part of the next phase of promoting the Congestion Free Network, we are going to focus strongly on expanding this new approach to defining congestion – so that it can actually be a useful measure of transport success, rather than something that suggests we do stupid things like building more (or bigger) urban motorways.

Highway 401 in Toronto

Right on Queue

Right on queue we get a full page spread from the Herald about traffic queues.

Wet weather, a serious crash and the post-Christmas rush combined to bring bumper-to-bumper congestion on long sections of highways and travel misery to holidaymakers.

Police described some traffic as a “rolling carpark” and urged calm as queues of up to 20km yesterday greeted motorists escaping Auckland, in the holiday hot-spot of the Coromandel Peninsula and north of Wellington.


Highways north and south of Auckland were crowded as thousands left the city for their New Year holiday.

Auckland Arts Festival Trust chairwoman Victoria Carter was among those caught driving north. A frequent user of the road, she said she had never known the queue to Warkworth to be as long.

“We got to the (Johnstones Hill) tunnel at 11am and there was a queue coming out of the tunnel as we arrived at it and we were hoping it was not the queue for Warkworth … and it was.

“We crawled to Warkworth at an average speed of 15-20km/h … It looks like the congestion stemmed from the traffic lights in Warkworth.”

Transport Agency spokesman Anthony Frith said a 20km northbound queue formed on State Highway 1 to Warkworth from 10am.

Last month, the Government approved a fast-track consent process for a $760 million extension of the Northern Motorway to Warkworth.

The Transport Agency has not set a start date for the 18.5km four-lane extension from the Johnstones Hill tunnels, but construction is expected to start between 2015 and 2019 and end between 2020 and 2025.

The traffic lights at at Warkworth are definitely a problem need to be addressed but that doesn’t mean it needs a full offline motorway to do it. The most prudent thing to do would be to build the bypass part of the project first by way of a small section of road from the existing SH1 to the P2W route as shown below. An additional small section of road to link where the bypass joins back to SH1 across to Matakana Rd would eliminate almost all through traffic out of Warkworth.


After those two pieces of work have been completed, we could then see just what impact they would have on traffic patterns and congestion and allow us to see if a full motorway connection between Puhoi and Warkworth is really needed. If that motorway still stacks up (which I doubt it would) then very little has been lost as only the blue section in the map above (about 1.3km) would have been surplus to requirements. However depending on how it was designed, that blue link could eventually be used as a link to another interchange which would mean the project would actually be of some benefit to locals as what is currently proposed would actually be longer for locals to use than the existing road.

I’m almost certain the only reason this isn’t being pursued is that those in support of the project know it would kill what little justification there is for the rest of the project.

BTW – to someone who has a physical copy of the paper, what’s that rubbish in the top right corner with flying cars. If there were about to come on stream then wouldn’t that kill the need for many of the upgrades even more?

Cartoon history of transport

A week or so ago, in a comment on his own guest post, NCD alerted us to this cartoon which I thought was brilliant. It is from French cartoonist Jean-Jacques Sempé and is from 1962 yet still seems relevant today.

Antarctic transport policy?

Wow there’s so many bits of news I want to comment on today and I don’t have time for them all so as it kind of relates to my post this morning I’ll go with this one. In parliament today Green MP Julie Anne Genter asked Gerry Brownlee about his stance on emissions and transport. It was following this news story from TV3 where he said”

I think climate change is something that has happened always, so to simply come up and say it’s man-made is an interesting prospect

So here is the debate today

The transcript is here.

This was what I thought was the best bit.

Julie Anne Genter: Can he name one place in the world where carbon emissions have reduced or where peak congestion has reduced as a result of new motorway construction?

Hon GERRY BROWNLEE: As far as I know, I would be correct in saying—because there are no motorways there—the Antarctic.


Brilliant question and one that left Gerry stumped because the reality is there isn’t anywhere that has built its way out of traffic congestion or emissions. Although perhaps Brownlee suggested it because in his mind hell would have to freeze over before he would accept that urban motorways don’t solve emission and congestion issues.

TomTom’s Congestion Index Report

TomTom have released their annual congestion rankings and reported that Auckland is the 17th most congested city in the world.

The City of Sails is fast becoming the City of Snails, and is rising on a list of the world’s most congested cities compiled by navigation firm TomTom.

The report, which compares congestion levels in 169 cities across six continents, found New Zealand cities were experiencing some of the biggest increases in congestion.

On the list of the most congested cities, Auckland is ranked 15th, Christchurch 17th and Wellington 37th.

New Zealanders now spend a staggering 101 hours annually in peak-hour traffic, with Auckland having the biggest increase in congestion across Australia and New Zealand.

The congestion level for Auckland is measured at 34 per cent in the last June quarter, up from 30 per cent the year before. In Christchurch and Wellington it is 32 per cent and 28 per cent respectively.

At its worst, Aucklanders are stuck in traffic for an average of 47 minutes for each hour driven.

That all sounds pretty bad but is it really? First it pays to look at how they calculate the congestion index. The reports – which can be found here  - state that it is calculated as:

With the publication of the TomTom Traffic Index we are aiming to provide the general public, industry and policy makers with unique and unbiased information about congestion levels in urban areas.

The methodology that is used in this report compares the travel times during non-congested periods (free flow) with travel times in peak hours. The difference is expressed as a percentage increase in travel time. We take into account local roads, arterials and highways. All data is based on actual GPS based measurements for each city the sample size is expressed in total number of measured miles for the period.

Straight away there is a major issue with this methodology and that is the comparison is based in just how fast you can travel if no one else was on the road compared to what happens at the during the peak period. This is a serious issue for a few reasons.

1. Cities that have a lot of all-day congestion won’t appear as bad on the report because there is less of a difference between free flow and congested periods.

2. Many of our roads have been built to try and handle peak congestion periods and are relatively empty off peak allowing for much faster speeds. The motorways are a great example as they are often bursting at the seams during the peak but can be comparatively empty off peak allowing for much much faster journeys. The Northwestern motorway is perhaps the prime example of this and is now going through another round of widening.

3. The biggest issue though is that by comparing travel times by in this manner, it ignores what the most efficient speed for moving vehicles is. By that I mean over the same stretch of road more people overall can be moved if they are travelling slow than if they are travelling 100km/h. This is something that was picked up strongly in the research conducted for the NZTA by Ian Wallis and Associates which looked at the cost of congestion. They noted the differences between the definitions of congestion as:

Various definitions of congestion were reviewed and it was found that the concept of congestion is surprisingly ill-defined. A definition commonly used by economists treats all interactions between vehicles as congestion, while a common engineering definition is based on levels of service and recognises congestion only when the road is operating near or in excess of capacity. A definition of congestion based on the road capacity (ie the maximum sustainable flow) was adopted. The costs of congestion on this basis are derived from the difference between the observed travel times and estimated travel times when the road is operating at capacity.

The graph below shows the engineering definition mentioned above.


4. The TomTom report misses one key aspect and that is the ability of people to travel congestion free. Investments in the rail network, Northern busway and even just some of the bus lane network in the old Auckland City Council area have led to dramatic rises in the number of people using Public Transport. In the case of the busway, it has seen the number of people crossing the harbour bridge increase from 18% in 2004 to 41% in 2011. These people are travelling almost completely free of congestion (with the notable exception of in the city centre) yet the amount of time they spend on their commute isn’t captured by this data at all because they are almost certainly not carrying a TomTom with them.


Instead of being a congestion index report, what the report really should be called is a private vehicle travel time variability report.

I do note some interesting responses in the articles about the report. In the herald we get

The New Zealand Transport Agency said it was working to improve traffic flow in cities through investment in public transport services and infrastructure, roading and facilities.

“Our investment in public transport is at unprecedented levels, having risen by over 20 per cent nationwide in just three years,” said agency spokesman Anthony Frith.

“We’re also investing in walking and cycling facilities that will get people out of their cars and onto their bikes or travelling by foot.”

In Auckland, the agency was investing $3.4 billion in the region’s transport system, including $1.6 billion for state highways, $968 million for roads and $890 million for public transport.

Well most of the increase in costs for PT are to pay for the NZTA’s share of the loan for the new electric trains. I’m not saying that isn’t welcome but not necessarily the massive investment suggested. Further a small fraction of that is going towards PT infrastructure.

And from Stuff:

Automobile Association principal infrastructure adviser Barney Irvine said a focus needed to be put on getting more out of the existing network.

“Public transport is an important part of the puzzle but it is only one part.

“The big thing is to try and get more out of the existing network.”

Mr Frith said several initiatives were in place to try to ease congestion in all of the cities.

Auckland had a $3.4b programme of investment in the region’s transport system from 2012 to 2015. This included improvements to state highways, local roads and public transport.

I agree that we need to get more out of the existing network and it’s good to see the AA acknowledging that.

Lastly if we really want to move people around then then the Congestion Free Network would allow people to do that completely free of congestion giving some real choice.

CFN 2030A

How much of a “cost” is congestion really?

Like all things in life, when it comes to transport there are always more projects being dreamed up than there is money available. So to determine just what should be built and when there needs to be some sort of prioritisation process. On the blog we try to sit between the two different aspects that make up this prioritisation process: the technical side and the political side.

The technical prioritisation process is typically done through a ‘cost benefit analysis‘, which I’m sure anyone who has read this blog for a while will have heard mentioned on many many occasions. There are clearly two sides of any such analysis: firstly the cost, which is the ‘easy’ part of the equation: what will it cost, what negative impact might it have? The benefit side is much trickier – clearly some transport projects, policies, services or whatever generate a benefit, but how to measure that benefit, put a dollar value on it and then be certain that dollar value benefit is greater than the amount we’re spending?

At this point transport experts make a number of subjective decisions, which are often passed off as objective facts. How much value to put on a minute of saved time? How much to put on a saved life? How to even work out how much time (or lives) will be saved? Will time even be saved in the longer run?

Typically most transport projects generate the vast majority of their measured “benefits” from travel time savings – the difference in some future year between the time it would have taken everyone to travel in a hypothetical “without the project” scenario and another hypothetical “with the project” scenario. Each saved minute by every person using the route adds up to saved hours, then a value is put on each hour and a whopping big number gets generated over the many decades long measured lifespan of the project.

This process has been the stock-standard approach for many decades in New Zealand and in many countries overseas – a supposedly objective way of making transport prioritisation decisions. Yet it is becoming questioned on an increasingly frequent basis. The latest critique is by transport expert Todd Littman, whose specific critique is of something called the “Urban Mobility Report” – a report prepared by the Texas Transport Institute which attempts to quantify the cost of congestion across all different parts of America.

Todd Littman’s critique is based around the idea that current cost-benefit analyses value of time ‘lost’ to congestion (and therefore the benefit of projects that may reduce congestion) far too high:

My analysis indicates that the UMR tends to exaggerate congestion costs and roadway expansion benefits, and undervalues alternative congestion reduction strategies. It uses higher baseline travel speeds and travel time values than most experts recommend (in fact, its baseline speeds often exceed legal speed limits on the roads evaluated), ignores the increased fuel consumption, pollution emissions and crash severity caused by high traffic speeds, ignores the increased external costs of induced vehicle travel, and ignores many co-benefits provided by alternative mode improvements, pricing reforms and smart growth policies. As a result, the UMR’s congestion cost estimates should be considered upper-bound values – when using such estimates analysts should apply sensitivity analysis that also include middle and lower-bound estimates.

These might be familiar critiques for blog readers. For example, we’ve noted that the supposed time savings from the Puhoi-Warkworth road would require someone to travel in excess of the speed limit to achieve. It was only earlier this year actually that NZTA released a report which highlighted that if you measure congestion costs properly, they might actually be ‘only’ around $145 million per year for travel time delay and a further $105 million for something called “schedule delay cost” (people travelling at times other than what would be ideal for them). This compared to an estimated cost of $1.25 billion using an unrealistic comparison with ‘free flow’ traffic.

Obviously the key next question is “well so what?” As explained below, the implications of over-valuing the cost of congestion are pretty vast in terms of how it skews the way we assess and prioritise transport projects:

Why does this matter? What problems will result if urban transport planning incorporates exaggerated congestion cost values?

Comprehensive and accurate valuation of congestion costs is important because urban planning often involves trade-offs between conflicting objectives such as between traffic speed and safety, and between automobiles and other forms of access. For example, expanding urban roadways may reduce congestion but tends to create barriers to active modes (walking and cycling), and since most public transit trips involve walking links, it also reduces public transit access. Exaggerating congestion costs undervalues other impacts and modes, leading to economically excessive roadway expansion and under investment in alternatives, resulting in a transport system which is less efficient, diverse, affordable, safe, healthy and equitable than optimal…

…Exaggerating congestion costs and undervaluing other congestion reduction strategies tends to result in economically excessive roadway expansion, and under investment in alternative modes, such as grade-separated public transit, and demand management strategies, such as more efficient road and parking pricing. This mattered less during the twentieth century when VMT was growing rapidly, so there was little risk of overbuilding roadways – any excess capacity would eventually be used, it was simply a question of when. However, now that automobile travel has peaked in most developed countries, and society is increasingly concerned about the external costs of excessive automobile dependency, overbuilding has become as economically harmful as under building roadway capacity.

So if we are over-valuing congestion costs, then what are better ways of measuring the impact of transport investment and prioritising projects? Well a good place to start would be by analysing the different factors which contribute to the “cost” that transport imposes on our lives – which interestingly highlights even the upper end of congestion costs as being fairly minimal in the scheme of things:


And here’s where we get to the key point:

…a congestion reduction strategy may be worth far less overall if it increases other costs, and worth far more if it provides other benefits. For example, a roadway expansion may seem cost effective considering congestion impacts alone, but not if it induces additional vehicle travel which increases parking congestion, accidents and pollution emissions. Conversely, alternative mode improvements may not seem inefficient considering congestion reductions alone, but are cost effective overall when co-benefits (parking cost savings, traffic safety, and improved mobility for non-drivers, etc.) are also considered. 

Until we fix the way we prioritise projects we’re going to keep making really stupid transport prioritisation decisions.

2013 Transport Monitoring Results

Buried deep within the agenda of last week’s Transport Committee meeting is a report on the results of both the annual screenline and congestion surveys. The screenline survey in particular is a very long running (back to the 1980s) survey which counts the number of people crossing various points – most particularly those travelling into the city centre by various modes. In general terms the screenline survey showed a small increase in the number of PT users across most measured points (although a reduced modeshare due to a jump in the number of people driving to the city centre) while the congestion survey showed that congestion in Auckland has been decreasing since 2009 (someone please tell the transport model!).

Public transport modeshare dropped back to just under 50% of vehicular trips into the CBD – still much higher than the other two screenlines at the western and southern edges of the isthmus:
Total PT patronage entering the city centre increased slightly to 34,130 during the morning peak hour. It is worth noting that since 2001 this total has increased from around 21,000 – a 62% increase.
One of the most interesting elements of the screenline survey is the breakdown by street for buses entering the city centre and how this has changed over time:

Fanshawe Street has really asserted itself as clearly the busiest point of entry for bus passenger to the city centre. This is not surprising given investment in the Northern Busway and that for many other areas people have clearly shifted from bus to rail as investment in the rail system has delivered an increasingly attractive travel choice. It’s encouraging to see that Symonds Street has “built up again” in terms of its numbers – after taking quite a hit when a large number of services were diverted to travel over Grafton Bridge. The numbers for Quay Street appear quite strange – big fluctuations up and down in almost every year. Are bus users in the Eastern Beach suburbs just a particularly fickle bunch I wonder?

The rail numbers were down slightly on 2012 – although the report notes that two fewer trains were counted in the 2013 survey (presumably services were slightly late and therefore outside the measurement window), which means that only a small reduction is actually a pretty damn good result.

The ferry information breaks down passengers by the different service they took – which gives us a useful understanding of how dominant Devonport and Waiheke are when it comes to total ferry boardings:
The report also notes key entry point for people walking and cycling – although unfortunately the quality of the table is really poor:

The report doesn’t explain what’s behind the fairly big decline in both walking and cycling between the two surveys in 2012 and 2013 – perhaps the weather was different (this is a once a year survey).

The report also notes results from a survey into congestion and travel time reliability indicators. The overall result is a decline in congestion since 2009:

I’m not surprised that congestion has declined in recent years as traffic growth has stalled while there has been a lot of investment in transport during that time. This reinforces a feeling that we have articulated many times on this blog: that future congestion forecasts are likely overblown. Travel time reliability has also improved in recent times.

This is really interesting and useful information – quite surprising that it was buried so deep.

Northern Motorway Pain

If you live on the North Shore – especially if you live north of Constellation – then I feel really quite sorry for you tonight. Following the incident this morning involving a police shooting parts of the Northern motorway remain closed. In particular the northbound lanes through the Constellation interchange which means that everyone heading north of that point will need to exit the motorway and cross Constellation Dr before re-joining the motorway again.

Commuters face slow trip home on Auckland’s North Shore

The NZ Transport Agency and Auckland Transport say congestion will be extremely heavy around the Constellation Drive interchange on Auckland’s Northern Motorway (State Highway 1) during this afternoon’s peak.

The Police have closed the northbound lanes of the motorway over Constellation Drive while they continue investigations into a fatal shooting.

The Transport Agency’s Regional Traffic Operations Manager, Kathryn Musgrave, says the northbound section of the motorway from Tristram Avenue has been re-opened only as far as the Constellation Drive interchange. All traffic will be diverted down the off-ramp at the interchange, across Constellation Drive, and on to the northbound on-ramp to rejoin the motorway again.

“There is going to be a lot of pressure on the interchange and the temporary layout we will have in place to try to keep traffic moving,” says Mrs Musgrave. “We’re expecting the afternoon peak to continue a lot longer than normal and people will have to be patient and drive with extreme care while we have this temporary traffic management in place. All road users will be affected – drivers as well as those people who rely on public transport.”

Mrs Musgrave says people do have a number of choices to try to avoid delays. They include leaving for home early to avoid the rush, delaying their journey to avoid the heaviest periods of peak, leaving the motorway earlier and using arterial roads as an alternative, and using the Northwestern (SH16) and Hobsonville/Upper Harbour (SH18) motorways as another alternative route to link up with North Shore arterial roads.

Auckland Transport says traffic will be slower than normal around the Wairau Road, East Coast Bays Road Constellation Drive, and there may be delays to bus services on many areas of the North Shore.

The NZTA, AT and Police are all working together to try to keep traffic flowing as freely as possible and road works on some arterials have finished early to alleviate congestion where possible.

All southbound lanes of the Northern Motorway remain open, but the NZTA appeals to drivers not to slow down as they pass the Police examination scene at Constellation Drive so that traffic continues to flow freely.

Bus users should have a little bit of a reprieve thanks to the busway however that will still have to fight with the rest of the traffic to enter the motorway again at Constellation.

While this is certainly a unique incident it is just one of many that we have been having lately that has caused havoc on our roads. To me it is just another prime example to show that we can’t rely on one mode alone to solve our traffic congestion issues and that means we need alternatives to help provide real travel choice to people of this city. The timing – on the eve of our launch of the Congestion Free Network – is a coincidence but is hopefully a timely reminder of how much it is needed.

I also note that none of the projects announced just over a week ago by the government will do anything to give people on the North Shore real choice. The additional crossing will serve to get a few more people to tail of the backlog a bit faster while the works around the SH1/SH18 interchange and the Greville Interchange only loosely refer to busway improvements.


How will our roads cope with 20% more vehicles on them?

Two more days this week have shown just how vulnerable our transport network is because of the lack of viable alternatives.

There was chaos on Auckland’s roads once again on Wednesday. Unlike the major incident a month or so ago on the Newmarket Viaduct, this time there appears to have been number of factors that combined together to cause massive problems for motorists. While there was talk about the bomb scare, personally I think the impact on traffic from would have been fairly minimal in the grand scheme of things seeing as Queen St has so few vehicles on it these days. Other factors like the horrendous weather and people trying to get away for an extra-long weekend are likely to have had a much bigger impact. However while the events that triggered the chaos might be different than what caused issues just over a month ago, the cause is the same, there are simply too many cars on the roads. Roads can only handle so much traffic before even the slightest incident can cause chaos and it feels like our roads are that level now.

So if our road network is already straining under the weight of cars it really makes you question how people can predict that traffic volumes will continue to grow substantially. Yet that is exactly what our transport models predict is going to happen. Even with the best case scenario of City Rail Link as well as improved bus infrastructure, our models predict that by 2041 the number of peopled moved by private vehicles in and around the city centre will increase by over 20%. The improved bus infrastructure will take further space away for private vehicles, which means those extra vehicles will be even more concentrated on some roads.


Of course as we know there are some serious issues with the modelling however even if just half that increase in traffic were to eventuate, what would happen to our roads. How will that change people’s perceptions of driving vs catching a bus or train? Despite what our models say, how realistic is it for us to substantially increase the number of cars that are able to around? Will we start seeing these massive congestion incidents turn from a being one or two times a month to a daily occurrence?

Unfortunately yesterday there was another incident, this time on the southern motorway where tragically someone lost their life. This naturally led to a lot of congestion as the motorway needed to be closed so that an investigation could take place.

As mentioned at the start, our transport system is extremely vulnerable to these issues. Building more and more motorways and wider local roads aren’t going to magically solve issues. Nor are tweaking traffic lights like suggested by John Roughan this morning in the herald (although at least he admitted that another harbour crossing isn’t needed). These measures will just allow people to reach the end of the congestion traffic queue faster. Properly investing in alternatives is the only real option we have that can give people some certainty to their travel times. Lets also not forget that these both occurred during school holidays, a time when there is usually a lot less traffic on the roads.

The REAL cost of congestion

There has been quite a lot of discussion recently about the “cost” of congestion, as well as pretty dire future projections in relation to levels of congestion 20-30 years in the future. But, compared to other elements of transport costs, how does congestion actually stack up? Todd Littman takes a look at this in a really comprehensive study that has been summarised on the Pricetags blog:

Comparing Congestion With Other Costs

The UMR report claims that traffic congestion wastes “massive” amounts of time and money, estimated at 5.5 billion hours and 2.9 billion gallons of fuel, worth an estimated $121 billion.

Described this way the costs seem very large, but measured per capita they appear more modest: 17 hours, 9 gallons and $388 per year, or less than three minutes, 0.03 gallons and $1.06 per day. These represent less than 2% of total travel time and fuel costs, which is small compared with other factors that affect per capita travel time and fuel consumption costs.

This indicates that congestion is overall a modest cost, larger than some but smaller than others:


Because congestion is just one of many costs, it is inappropriate to evaluate congestion reduction strategies in isolation: a congestion reduction strategy may provide far less total benefit if it increases other costs, and is worth far more if it reduces other costs or provides other benefits.

For example, roadway expansions may seem cost effective considering just congestion impacts, but not if wider roads induce additional vehicle travel which increases other external costs. Conversely, improving alternative modes may not be cost effective based only on their congestion reductions, but are cost effective overall when co-benefits (parking cost savings, traffic safety, or improved mobility for non-drivers, etc.) are also considered.

Somehow we need to get past using congestion as the primary success/failure measurement for transport. After all, not only is it seemingly relatively minor in the scheme of things, but there’s a fairly good argument out there that congestion doesn’t hold back economic productivity:delay-vs-gdpUltimately it’s hard to work out what the real cost of congestion is, but I’m pretty sure it’s WAY less than we assume.