A lot of people in transport circles like to talk about induced demand, which basically means "if you build it, they will come" or Discworld's celestial birdhouse, which ultimately evolved into a post-office. This is a very important thing in those transport circles because it helps explain why adding roads increases congestion but both that and induced demand more generally sound a bit stupid to the general populace ("if you build it, they will come" is used dismissively). They do make sense (supply increases => lower cost => quantity demanded increases... with "cost" not necessarily being financial). But I was thinking about induced demand in terms of choice... if you build another route somewhere then what happens? Now you have to choose between several different routes and these are dynamic systems (the textbook also discusses 'the difficulty in thinking through many steps of reasoning involved in some complicated processes' from page 611). People probably resort to quick heuristics and end up broadly choosing the same routes. This, I think, is the Braess Paradox:
"For each point of a road network, let there be given the number of cars starting from it, and the destination of the cars. Under these conditions one wishes to estimate the distribution of traffic flow. Whether one street is preferable to another depends not only on the quality of the road, but also on the density of the flow. If every driver takes the path that looks most favourable to him, the resultant running times need not be minimal. Furthermore, it is indicated by an example that an extension of the road network may cause a redistribution of the traffic that results in longer individual running times."The suggestion, in some sense (and I am sure I read something like this recently but I cannot find it), is that when it comes to roads, the situation is more that people don't make the optimal choices rather than they shut down when confronted by too many choices. This is good news because it suggests that adding more choices could be useful provided that they are the kinds of choice that can be optimally evaluated. However, in trying to re-discover the Braess Paradox, I also encountered this:
You might think that increasing investment in public transit could ease this mess. Many railway and bus projects are sold on this basis, with politicians promising that traffic will decrease once ridership grows. But the data showed that even in cities that expanded public transit, road congestion stayed exactly the same. Add a new subway line and some drivers will switch to transit. But new drivers replace them. It’s the same effect as adding a new lane to the highway: congestion remains constant. (That’s not to say that public transit doesn’t do good, it also allows more people to move around. These projects just shouldn’t be hyped up as traffic decongestants, say Turner and Duranton.)Basically that article had earlier suggested that adding lanes initially results in a decrease in travel time, so more people join in (whether by switching away from public transport, moving further away, making more trips than before) and thus after some time you return to where you were before. Taking away roads, though, causes behaviour to change differently with people switching to public transport. In this sense, for public transport to work as a solution to congestion, it must be within the context of using it to increase capacity and then closing the roads so that people have something to switch to. In Auckland, peak trains can often be extremely full at the moment and one of the issues that people identify as motivating the CRL and Light Rail is capacity (limits being reached, immediately and soon respectively). Also, if public transport improvement allows congestion to remain constant, could it be the case that congestion can be preserved even under population growth through public transport increases?
That article also mentions congestion and parking price changes. These are good ideas in a simple sense. After all, we shouldn't have people on the roads if the trip they are making could be done some other way. This is another choice problem: internalisation of external costs (above identified as the issue in the Braess Paradox). I won't explain how the charges work or their principles because they're at the end of the Wired article but I should note that this is where caution needs to be exercised to avoid creating equity issues. For a city like Auckland that is really several suburban centres like Otahuhu, Papakura, Parnell, Grey Lynn or wherever so there is an opportunity to recognise that what is appropriate in some areas isn't elsewhere... congestion pricing and parking are, thankfully, only really proposed for the CBD, which I don't think I am atypical among South Aucklander's in having only visited rarely outside of uni associated trips. The point is congestion hurts everyone but pricing it involves flat rates which are much more affordable for some than others. For more centralised cities this presents a problem but one would hope that public transport would be more affordable than is the case in Auckland. Ultimately, I would like to see two things. Firstly, that HOP cards be able to be used for parking. Secondly, that accompanying measures like congestion pricing and increased parking costs a community services concession be added to the likes of HOP (although this may not help the working poor). But the specific point is that such internalising measures removes arbitrary subsidies and create real choices.
Transport's a critically important part of not just urban life but rural life too. It is also one of those areas of life that I firmly believe benefits from a greater variety of choice. However, that doesn't mean (as we have seen) there are no complexities. In transport, the choices that matter are about frequency, reliability and mode. I could have talked about Marketing Myopia here (indeed, Levitt discussed trains... freight as far as I recalled) in his seminal article, because it's basically the same idea in reverse and thus continued my defence of the validity of Business 101. The trouble is that we're myopic in general... as Transportblog noted, for some reason the importance of personal choice in their arguments for transit is ignored in order to hammer home bloody-minded and misplaced anti-leftist condemnations of anything that doesn't involve 1.2 humans and several tonnes of car. I believe the final word on the matter comes from Over the Hedge:
That's an SUV.
It's so big... how many humans fit in it?
Usually? ... One.