Building more roads

I've recently read several posts like, http://www.politics.co.uk/blogs/2014/12/01/george-osborne-s-15-billion-road-to-nowhere, which say "if there's congestion, building more roads will cause more car travel and more congenstion and won't really help".

I was inclined to agree with the general conclusion, but I didn't actually understanding the reasoning.

Eventually I read the 1994 DFT report http://persona.uk.com/A21Ton/Core_dox/P/P14.pdf, which was a bit of a slog, but made it a bit more clear to me.

The report itself

One thing that struck me, is how rarely I read reports like that, and how competent it was: clear what it was saying, what it was based on, who endorsed it, and what they thought DFT should do. I realised how much government process goes on in reports like this that I know NOTHING about, and I wish evidence-based policy making was a lot lot lot more high profile!

More roads

The gist of the report is, DFT evaluation of the benefits of new road schemes usually rest on the assumption of, "assuming the same volume of traffic, how much benefit will there be to this extra road building". And extra traffic was assumed to be a small effect that was usually not significant. But the report says that's not true: demand is elastic, so better transport means extra traffic (both from short term effects like people choosing to drive, and long term effects like people building new companies in places with good transport links)

I think what I'd not understood was why that mattered. I'd unconsciously assumed that more cars had an inverse relationship to travel time, so more roads would translate into better travel -- either quicker journeys for existing travellers, or making possible journeys for people who previously couldn't travel or travelled a different way. But I couldn't see why it mattered which.

However, I think what the report is trying to say -- which if I'm right, I'm puzzled wasn't explained more clearly in a summary at the start -- is that my unconscious assumption was wrong. It's more like, up to a certain point, more cars don't really slow anyone down at all (a motorway can handle two cars travelling at 70 just as easily as one). But past the point where you start to get congestion, it slows down LOTS for EVERYONE. So congestion doesn't just mean "too many cars", it actually makes the travel time WORSE.

Even, maybe, something like "if everyone tries to travel at once, it takes four hours for everyone, but if half the travellers set off immediately and half in two hours, it would take two hours for everyone". I'm not sure if that's true, but it seems what is trying to be said. But I'm not at all sure I'm understanding this right -- is that actually right?

If so, "more roads means more cars means more congestion" specifically makes sense: roads reach a level of congestion people stop travelling on them at, and if you build more roads, you get more people, but everyone's journey still takes twice as long as it would on empty roads. (Until you reach the point of enough roads for everyone in the area who wants to commute at once, which is what new road building schemes imagine, but the report says is basically impossible.) And the report says, if DFT new-road evaluations allowed for that, a lot fewer of them would be evaluated as worth the cost.

Is that actually right?

Disclaimer

I would prefer it, both for myself and the country as a whole, if public transport were so convenient that everyone preferred to use it all the time, not relegated to second-class-status. But I want to actually understand the evidence for things, not just assume the evidence that gives the conclusion I hoped for is always right.

Where do I stand religiously? Is there any particular religion I'm not.

Where do I stand religiously? Still atheist, about like you'd probably expect. Although more thoughts in a follow-up post.

Is there any particular religion I'm not? I think that's a question which is interesting in potentially several different ways.

I generally expect a religion to be something like "some combination of a culture, a belief system about the supernatural, and a moral framework".

Culture-wise, I'm very much english and vaguely CoE. I do Christmas, and Easter, and other english religious-instigated festivals, and I'd happily do other ones instead if I lived in a culture where that was normal, but it would feel very strange not to do ANYTHING for Xmas. I went to CoE things with school sometimes, and learned hymns and so on, and I hadn't realised how much I'd subconsciously absorbed how I expected religious services to work until I actively compared notes with people who had absorbed _different_ expectations: not just the obvious things, as the things I didn't even think to question (of course you bury people in the churchyard, right?)

And I'm also sopping up a steady trickle of Jewish culture from Rachel and Rachel's friends, and I really value having the experience of another culture, although I doubt I'd get to the point where it would displace my background as my primary religious-derived culture (unless I specifically made an effort to do so).

So in one sense, you might say my atheism is "CoE with the God taken out", although that's not really fair to CoE, nor to people who don't believe in God but come from different cultural traditions.

The other way of posing the question is, what, specifically, don't I believe? Well, basically, "anything supernatural" (where supernatural means something roughly like "outside how we expect physics to work",but you probably know what I mean better than I can describe). Which was always presented to me as a defining feature of religion. With emphasis on "and therefore you should obey this set of rules even if they seem horrible". That's what I'm atheist against, that's what I'm not. Although, my terminology may not be right, because that's the background I'm coming from, but I encounter more religious people for whom that is a small or non-existent part of their religion.