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.
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.
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!