Stephen Rees's blog

Thoughts about the relationships between transport and the urban area it serves

I-5 closure shows we’re adaptable

with 2 comments

Seattle PI – Opinion

Our collective “need” for highway capacity is about as certain as our “need” for bottled water.

It is instructive that we have known about how traffic reacts to both expansion and contraction of highway capacity for many years. After all there are plenty of examples and experience wherever you go. Yet our politicians seem to be impervious to the lesson and they keep on saying that we “need” more highway lanes, more roads, or will be overwhelmed. That without more concrete and tarmac, growth will stall, or the we will see the economy stagnate or – horror of horrors – the Americans may continue to accommodate their import container traffic in their own ports.

Engineers still believe some very poorly designed models based on comparisons with gravity, that treat traffic like a flow of water. In which water finds its own level and demand never reacts to changes in the network other than rerouting. Which we know does not represent what happens. In fact, traffic is more like a gas – it expands and contracts to fill the space provided. The model in this region can in fact do no more than tell you about longer distance travel across the “screenlines” (essentially water bodies and some municipal boundaries) at the morning peak hour on a weekday. In fact the network now sees more traffic in the afternoon peak. But most importantly, it assumes that the volume of traffic is constant, and is simply a function of population and land use.

Indeed, the way the model works is actually not very accurate “out of the box” and it has to be “calibrated”. What little data we do have shows that the model will not  accurately do even the limited task we set it without adjustments to make it fit the observed flows.  For example it assumes that people travel to jobs that are close to them, but we know that is not true, so the calibration allows for the extra “attractiveness” of downtown. Except of course, downtown is now much less significant a destination for the morning peak flows than it was when the model was calibrated.

Maybe the big lesson of the I-5 experiment is this: It isn’t too little capacity that causes gridlock — it’s transportation systems that don’t give people choices.

Or the choices it does offer them are just not good enough to enable them to switch modes. That is the case here for transit, I am afraid. And that is why I constantly harp on the theme of improving service. Because that is what deters drivers from switching modes. As long as transit is slow and unreliable, and inconvenient compared to driving, only around 10 to 11% of the trips will be made that way.

And expanding road capacity – or refusing to reduce it – ensures that car dominance will continue. This is not rocket science.

If we spend money on improving our transit system – buying more buses, changing streets so the buses have priority over single occupant vehicles, building light rail systems utilising existing tracks wherever possible and keeping cost down to expand coverage as widely as we can, then we will see mode shifts. Continuing to do what we have done for the last fifty years will see the same results we have always seen. Expecting any other outcome is madness.

And if we are really serious, and we really want to reduce the terrible carnage of driving (for the US its death toll is far greater than the Iraq war) then we will use the market – a pricing system – to actually charge users what it costs to accomodate their cars and their “need” to drive them everywhere. For right now, the market signals are that we should acquire cars (they are getting cheaper, in real terms, and more efficient) paying up front for tax and insurance too, so that we have invested a considerable fixed sum, and thus the perceived marginal cost per trip is very low. If people think at all about money when they drive their cars it is first parking and then gas cost that will come to mind. What they really care about is time. So what we need to do is make the car less convenient (reduce road space for cars, cut parking provisions) and raise its price at the same time as we make transit much more attractive.

Indeed, I think it is essential to have some spare capacity on the transit system before you try to persuade people to use it. So some of the new trains may well appear to be a bit empty at first. That’s alright. We can stand a loss in the first few years if we can fill it in the long term. And you know that our current experience shows that when you do provide a good alternative, you don’t have to market it at all. It sells itself. Word of mouth is your best friend. I would get rid of the marketing and PR people altogether. Make the people who run the system your spokespersons and salespeople. And allow them to be honest – that builds trust, not cynicism with spin doctors. Above all give them a really good product – fast, comfortable, safe and reliable. The colour you paint it, and the name you call it, matters not one whit.

Written by Stephen Rees

August 21, 2007 at 6:33 am

2 Responses

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  1. I suppose that the corollary to the above is that it is hopelessly difficult to provide a high level of service to destinations that are dispersed – so the role of / interplay with muncipal zoning also factors highly in the equation.

    ron c.

    August 21, 2007 at 2:53 pm

  2. I don’t know about “hopelessly”

    I did make a suggestion in another post today.

    And it is not just land use zoning. The sort of dispersal of dense development we see in some suburbs – leaving long gaps between developments – looks nice but makes conventional transit expensive. Contiguous development in corridors works better from a transportation perspective. Similarly, the current way we design suburbs, to deter through traffic on residential streets, makes getting to and from the bus stop lengthier than it need be, although people do resist buses on their street and lanes past their backyards (so there are more direct walking routes). So its not just the zoning, its the layout and pattern too.

    But the simple fact is that we have not been building transit oriented development in general – though there are creditable exceptions. But even those did not get good service – Port Moody for example is still waiting for its LRT long after most of the new residents moved in to their walkable neighbourhoods. Because the Canada Line suddenly trumped the Evergreen Line – as though the Olympics were actually going to be a significant event!

    Stephen Rees

    August 21, 2007 at 3:24 pm


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