How traffic engineering standards can break our cities

Many of you will know me as just a facetious blogger who spouts off about random things from time to time. This is indeed true.

What is also true, however, is that in a previous life I worked as a transport engineer. While nowadays I work primarily as a transport planner and an economist (roles in which I have more of a policy focus), from time to time I still find myself getting down and dirty with the application of basic traffic engineering principles.

Over time these experiences have led me to form the opinion that the traffic engineering profession in New Zealand is, shall we say, pretty much broken. It’s broken largely because “standards” have been progressively used as a substitute for thinking. And we’ve basically chosen the wrong standards. We’ve chosen traffic engineering standards that 1) fail to acknowledge basic scientific/economic principles, such as minimum parking requirements and 2) prioritise vehicle mobility ahead of other more important socio-economic outcomes. Many of these standards have profoundly negatives impacts on our cities.

In this recent post Matt presented one case study of a road re-design in Washington, in which he contrasted the designs for a corridor put forward by traffic engineers versus transport planners. Needless to say the options presented by the latter (illustrated below) appealed more to all of us here at TransportBlog.

Washington Freeway replacement Planner options

Not only do the options developed by transport planners have greater aesthetic appeal, but three of them also provide for additional land use development within the transport corridor. Indeed, traffic engineering practises that are currently applied in New Zealand (and to a greater degree Australia) do not even stop and consider the value of land. Land is so dam valuable, and the efficiency with which we use it determines, to a large degree, the productivity and amenity of our urban areas.

It would not be too factitious to suggest that many traffic engineering standards seem to presume that land is free. It’s as is if there are dutch pixies at the bottom of the garden who are manufacturing land from the sea.

One example of such a standard is the concept of the “design vehicle”, which I will focus on for the remainder of this post. Of course there are many other examples of traffic engineering standards, such as minimum parking requirements, which have been discussed before on this blog and that also have hugely negative consequences. The reason I want to focus on the “design vehicle” concept is because it does not receive much attention. And also because it has a fundamental impact on so many things.

For those who are not familiar with the “design vehicle” concept let me briefly explain. The “design vehicle” is a phrase that typically describes the largest, heaviest (per axle), and/or least maneuverable vehicle that is expected to use a particular part of the road network. Naturally, the physical footprint required to accommodate this design vehicle subsequently defines most aspects of the physical road geometry, such as turning radii and pavement design. For this reason, the shape of our road networks is very much defined by the design vehicle that is chosen.

You can read up on some of the design vehicle standards recommended by the NZTA here. The design vehicle for the standard street is typically some form of medium rigid truck, such as what is commonly used to move furniture. I’ve illustrated the physical dimensions of this vehicle below.

Medium rigid truck

The choice of design vehicle can have a massive impact on the degree to which a particular road supports, or more commonly undermines, socio-economic outcomes in urban areas. Working with a large design vehicle effectively puts paid to the types of narrow lanes and tight intersections that are ubiquitous in European cities (as an aside I’m writing this from Amsterdam, having just traveled through Paris, Porto, and Barcelona). Here’s a photo of my bicycle and I in a narrow lane in Barcelona.


Alternatively, if you can convince your traffic engineer to use a smaller design vehicle then you can reduce the physical footprint of the road network.

In my experience, however, the traffic engineering profession has developed a “gotcha” for anybody who dares suggest a smaller design vehicle be used. The “gotcha” is service vehicles, such as garbage trucks and emergency service vehicles. That’s right, the humble garbage truck, they argue, needs comprehensive access to every urban nook and cranny. In turn, our urban nooks and crannies are designed around the needs of the garbage truck, which is – perhaps needless to say – rather large.

In this way, it is actually relatively difficult to argue for tight lanes and turning circles in many new developments in Auckland, by virtue of the need to provide access for service vehicles. Now I would have less issue with this standard if someone, somewhere had actually sat down and considered what the benefits and costs of such a standard were. Typically, traffic engineering standards require more land, which is a cost. The benefit, I presume, is increased mobility. Hence it should be fairly straightforward to undertake some form of benefit-cost analysis of the regulation to work out

Now take a look at the photo below, which shows a relatively common streetscape from Amsterdam.


You will notice a cycle lane running from the bottom left of the figure towards the right hand side of the figure. If you follow this cycle lane closely then you should be able to make out the back of a small vehicle that is parked in the cycle lane just outside the shop. This is, my friends, a rubbish truck.

Which brings me to the point of this post. Amsterdam, like many European cities, designs their urban areas to deliver a broad range of socio-economic outcomes, such as walkability. This in turn requires narrower lanes and tighter intersection footprints. In response, they have effectively had to “down-scale” their rubbish trucks.

In this way I think the traffic engineering profession in New Zealand and Australia has put the garbage cart before the community horse. More specifically, instead of designing the communities we want and then selecting the vehicles that can integrate with that design, we choose the vehicle first and subsequently design our communities around their needs. I suspect our approach is very, very economically inefficient insofar as it increases the physical footprint of the road network. Remember, in cities, space is always expensive!

The Infernal Combustion Engine

Statistics NZ have been publishing yearbooks since 1893 which they say provide “a comprehensive statistical picture of life in New Zealand”. If you’re prepared to but a bit of effort in going through them you can some superb historical data so they are a really valuable resource – although going through them is made much easier by them having been digitised and therefore allowing people to use the browser search function.

So I was collating some information from them when I came across this piece of commentary in one of them. See if you can guess what year it is from (some of the dates in the piece should help to narrow it down)

Infernal Combustion Engines

Cars are one of the biggest threats to the global environment. They contribute to global warming, oil spills and water pollution, road congestion in cities, and noise and air pollution. The transport sector is estimated to be responsible for 40 percent of New Zealand’s greenhouse gas emissions. In the developed world cars account for an estimated 20 percent of the world’s total energy consumption. When the energy to build and maintain cars and roads is taken into account this figure could be as high as 50 percent.

Cars are particularly inefficient vehicles. In New Zealand the average car currently manages a mileage of 100 kilometres per 10 litres. To reach the Government’s target of a 20 percent reduction in greenhouse gas emissions by the year 2000, this would have to be cut to 100 kilometres per 3.5 litres. Cars are also inefficient users of road space, carrying an average of only 1.2 passengers. A bus, using about twice the amount of road space, can carry up to 50 passengers.

New Zealand has the second highest rate of cars per capita in the world, with petrol consumption increasing by 4 percent a year. Car-related taxation, such as registration fees, import duty and road taxes, are low by international standards. Deregulation of the transport industry has meant the scrapping of some commuter services, with many others at risk; while, for a number of years, trucks have been gradually replacing trains and coastal shipping in the freight transport sector.

There are many suggestions on how to reduce New Zealanders’ reliance on cars. In Holland new taxes will add 50 percent to the cost of owning and running a car and extra taxes are being developed for heavy users.

Between 1989 and 1990 in Paris, 100000 parking spaces were eliminated to discourage commuters from driving into the city. A light rail system has been installed in Sydney to shuttle people around the city quickly, cheaply and cleanly. Other suggestions include more pedestrian only malls, wider footpaths to lessen road space and improvements to existing public transport systems to make them more attractive to commuters.

New Zealand’s high car use is an important issue that needs to be addressed. If New Zealand is to reduce its greenhouse gas emissions 20 percent by 2000, action must be taken soon. The longer the problem is ignored, the more drastic the measures will have to be.

The piece was from 1992 yearbook but what I found remarkable was how similar it is to many of the things we are saying now including:

  • That cars are a big issue for the global environment including air, water and noise pollution.
  • That they seriously contribute to congestion which is in large part due to being an inefficient use of space.
  • That we have an over-reliance on them leading us to us having one of the highest car ownership rates in the world.
  • That improved improvements to public transport, the pedestrian environment and levels of parking can make alternatives to driving more attractive.

So it’s also interesting to see what has happened to car ownership since that time, again thanks to the yearbook data. In 1992 there were ~1.5 million cars in New Zealand while in 2012 that number was ~2.3 million, an increase of ~800,000 cars. There has also been an increase in the number of vehicles per capita with it having increased from 0.43 to 0.52 over the same time period – although that is down slightly on the peak of 0.54 seen in 2007.  Note this is just the number of private cars and so doesn’t include the likes of rental cars, motorcycles etc. Also the break in the data is from 1987 when there was a change in the way vehicle registrations were counted.

Car Ownership from 1925

But even more interesting is that it isn’t just that we have more cars than we did in 1992, but the cars we buy now generally have larger engines with the percentage of them having a cc rating of more than 2000 increasing from 19 to 34% but peaking at 44% in 2004. This is of course in line with the Jeavons Paradox that as we improve the efficiency with how we use a resource that we increase the overall use of it. In this case as we make vehicles more efficient we buy bigger vehicles and drive more. The big spike around 1990 was the result of making it easier to bring in second hand cars

New Registrations by engine size

Pecentage of New Registrations by engine size

I guess that means we haven’t done a great job at combating those infernal combustion engines.

Trends in Car Fuel Efficiency

This is an update of a (guest) post I did in December 2012 – I’m planning to keep updating it each year.

These days, most people are aware (often painfully so) of petrol prices being over $2 a litre, and much higher than they were a decade ago. It costs more to run cars than it used to, and consumers’ wallets haven’t really kept up with the cost increase. Unsurprisingly, there’s a heightened awareness about fuel efficiency, which we could also call “fuel economy” to highlight the fact that people are generally more worried about the cost implications.


“Lab tested” fuel efficiency for new vehicles: US trends

The EPA did a fascinating study on fuel efficiency trends in US vehicles manufactured between 1975 and 2013, available at Essentially, car engines became 50% more efficient over the 39-year period. However, over this time, cars became much heavier, needing more energy to move. US cars became more efficient from around 1975-1985 as the oil shocks hit and the government started to regulate fuel economy (the Corporate Average Fleet Economy scheme, still around today). Then, fuel economy actually got worse for 20 years – engines were getting more efficient, but this Americans were driving increasingly heavy cars, and switching to SUVs (or “trucks” as they call them in the US) in their millions. Since 2005, there have been some significant improvements, as high oil prices hit home.

This is what happened to the fuel economy of new American vehicles between 1975 and 2013. Note that this is in “litres per 100 km”, so a lower number means a more efficient car. I’ve calculated the figures for cars, trucks and both of them combined and weighted by production.

US fuel efficiency trends for new vehicles


US fuel economy standards for new cars stayed the same for more than 20 years, but the Obama administration has begun to tighten them, starting with the 2011 model year, and with major incremental improvements proposed through to 2025.

I think it’s interesting to note, though, that fuel efficiencies started to improve again, well before the tighter CAFE standards began to came into effect. Americans began to shift towards more efficient cars of their own volition. They also started to buy fewer trucks. The market share for these massive vehicles peaked at 48% in the 2004 model year, and has now fallen back to 36%.


“Lab tested” fuel efficiency for new vehicles: New Zealand trends

NZ doesn’t have a long-term data series like the US, but the Ministry of Transport now collects fuel efficiency ratings for vehicles as they enter the fleet. This shows that the light vehicles coming into New Zealand (including cars, vans, light trucks etc) have been getting more efficient. Cars entering the fleet today are at least 10% more efficient than in 2005, on average. You can see the downward trend in fuel use in the graph below. Actually, the graph shows CO2 emissions, but these are directly proportional to the amount of fuel used.

NZ fuel efficiency trends for new vehicles


“On Road” fuel efficiency

The data I’ve shown above is lab-tested, and only applies for vehicles entering the fleet. There are a couple of factors to consider when applying it to the real world, and across the entire vehicle fleet. Firstly, cars tend to use more fuel on the road than the lab readings suggest (congestion and air conditioning being the two main culprits). Secondly, the data above is for cars being produced (or imported) in each year, so those fuel economy values can change much quicker than when you’re looking at the total fleet, as for the NZ data. If Priuses were the only new cars sold in New Zealand in 2013, it would still take quite a while before we’d see any noticeable difference to the fuel economy of our entire fleet of 3 million vehicles.

In fact, information from the Ministry of Transport shows that the NZ light vehicle fleet has on-road fuel economy of around 10 L/ 100 km, and this has remained stubbornly flat over the last decade (notwithstanding an apparent drop in 2012, which seems to be down to data issues: the MoT reckon the drop “seems too large to be credible”).NZ on road fleet wide efficiency

If we take a look at some Australian data, we can see that they’ve actually had no improvements in on-road fuel efficiency in the last fifty years. Australia’s a fair bit hotter than NZ so we can imagine that they took to air conditioning like a shrimp takes to a barbie.Two things to note there – firstly, the MoT data shows “on-road” fuel efficiency, or what our cars have actually achieved on our roads.


So what are the takeaways here? New Zealanders (and Americans) have started buying more fuel-efficient cars thanks to higher fuel prices in the last decade, but the improvement hasn’t been stunning – 10% is nothing to write home about, and there hasn’t been any noticeable effect on how much petrol the overall car fleet uses. In fact, international comparisons make it likely that decades of technological progress have done almost nothing to reduce how much petrol we use. Engines have gotten better, but cars have gotten bigger.

Most of our cars come from Japan, and fortunately they tend to be a bit more efficient than those in the US – not that it’s helped us much. But we’ve jumped on board the SUV bandwagon, and we’ve got a higher proportion of those in our fleet than just about any other country besides the US. We’re also madly in love with big cars like the Holden Commodore and Ford Falcon. The average engine size for NZ cars is a pretty hefty 2.4 litres.