The general idea is that congestion dissuades some amount of commuters from using the road at congested times. When additional road capacity is added, those people will shift their commute time, or commute mode, or commute route to re-congest the road. (Time, mode or route is the "Triple Convergence" or latent/induced demand.) But in certain contexts like LA or London it's not possible to build enough road capacity to eliminate congestion. So building additional road capacity has the effect of (a) not reducing congestion and (b) reducing usage of public transportation. And (b) causes additional problems for the efficiency that public transportation.
The counter-intuitiveness is why it's a paradox. And the context probably matters for when this theory applies. But supposedly it happens to lots of developed cities. The original study on London was looking at when ~80% of commutes happened by transit. But LA is trying to improve its transit infrastructure because partly because this problem.
After reading the article I have to point out, from the "Restrictions on validity" section, that it "only applies to regions in which the vast majority of peak-hour commuting is done on rapid transit systems with separate rights of way".
So for most cities outside of NYC, this paradox supposedly does not apply (even though I feel it has some bearing).
Regardless, the general principle behind the paradox is induced demand (http://en.wikipedia.org/wiki/Induced_demand) - which, regardless of the share of transit users, will always apply to highway projects.
In other words, I believe that to the extent new lane capacity is filled as soon as the construction workers pick up their cones, it is because economically and/or socially useful things are happening. Otherwise, why would any of us drive anywhere at all?
Third, economic arguments are a little dicey for driving because driving is filled with externalized costs, subsidies, overoptimistic assumptions, and dependent utility. Driving creates noise and pollution (and it appears that the pollution is more deadly than crashes) but drivers don't pay that cost. There's personal crash risk, but people tend to assume that they are careful drivers and hence less likely to crash than the norm. The cost of the roads themselves is currently subsidized from the general fund; it's not a huge external cost, but it's a cost. Driving also creates (perceived) danger to people biking and walking; that tends to encourage them to also drive for their own (perceived) safety, even when they otherwise would not, and the congestion costs of driving also delay bus transit, making it less useful (it's already slower because of all the stops; traffic jams make it slower yet).
Instead, because the city is optimized for cycling and public transport, I live in a culture where taking even public transport is frowned upon if the bicycle commute is < 30 mins (and even an hour, perhaps).
I think this argument applies to many things. In the city where I live, Amsterdam, there's (almost) always a supermarket at walking distance (or a 5-10 min. bike ride). In fact, this is true for the whole country, as far as I know. 'Hypermarkets' like wal-mart or Carrefoure never really took off. The reason for this is partly culture, but largely it's because of regulation that protects smaller shops.
Most people consider it a very good thing that we can walk to the supermarket and that we are, in effect, 'forced' to have a healthy lifestyle and culture.
Anyways, I just wanted to share how the fact that streets will fill up and hypermarkets will most likely be successful doesn't mean that this is a good thing, or that it's in our best interest.
Moreover, road safety is not fixed but rather dependent on the speed at which drivers drive on the road. Thus, if a roadway design causes drivers to drive slower on road B as opposed to road A, road B may be safer even if it would be less safe than road A if people drove the same speeds on both roadways. There is nothing particularly counter intuitive about this type of theory at all.
Also perceived danger to oneself doesn't take into account the risk one poses to others. This issue of externalities is what makes these 12 foot lanes so dangerous. As noted in the article, if drivers are driving slower, they are far less likely to kill or seriously injure pedestrians. And since F = (.5)mv^2 this is exactly what we'd hypothesize. Pedestrians are a non-issue on the rural highways that the 12 foot lane and other state road design measures are based on. But in the middle of a dense city, higher speeds, even if they aren't any less safe for the drivers, are far less safe for pedestrians and cyclists, not to mention far more unpleasant to be around. It is this concept, more than anything else, that traffic engineers are so often obtuse to.
And driver-less cars will have to be able to navigate the existing 10-foot lane roads anyways to be commercially viable, so I don't see how that is an issue.
Without the expectation that people will compensate for it, making the lanes narrower does make it actually more dangerous. There will be less space between each vehicle and less space between the vehicle and pedestrians on the side of the road, which reduces the amount of space available to avoid an obstruction, the amount of reaction time available to avoid a collision, etc.
> Also perceived danger to oneself doesn't take into account the risk one poses to others.
That is a counterargument to your position. If drivers aren't bearing the full risk then an increase in risk should cause them to undercompensate, not overcompensate.
> And driver-less cars will have to be able to navigate the existing 10-foot lane roads anyways to be commercially viable, so I don't see how that is an issue.
It is possible to be less safe without being negligent and that difference is still measured in human lives.
I think you're being downvoted in part because the linked article refutes your viewpoint. There's even a pullquote saying "States and counties believe that wider lanes are safer. And in this belief, they are dead wrong." Followed up in the text by "Or, to be more accurate, they are wrong, and thousands of Americans are dead."
And "The lane widths in the analyses conducted were generally either not statistically significant or indicated that narrower lanes were associated with lower rather than higher crash frequencies."
> This research investigated the relationship between lane width and safety for roadway segments and intersection approaches on urban and suburban arterials. The research found no general indication that the use of lanes narrower than 3.6 m (12 ft) on urban and suburban arterials increases crash frequencies. This finding suggests that geometric design policies should provide substantial flexibility for use of lane widths narrower than 3.6 m (12 ft). The inconsistent results suggested increased crash frequencies with narrower lanes in three specific design situations. Narrower lanes should be used cautiously in these three situations unless local experience indicates otherwise.
It it turn builds on, for example, results by Hauer, et al, Strathman et al. which appear.
You then raised another objection, which is, I believe, that a 10' lane causes people to use alternate routes because of decreased capacity on those lanes, so there are simply fewer people on the 10' lane roads to cause accidents.
This may well be. It's a subtle network effect that is hard to analyze, and not covered in this article. (The article does comment that capacity is unchanged, but I think its literature citations are weak. It quotes Petritsch who in turn quotes a summary of an unpublished literature search.)
However, your objection is not what was refutated. AnthonyMouse proposes that narrowing lanes lead to a higher accident rate since it "reduces the amount of space available to avoid an obstruction, the amount of reaction time available to avoid a collision, etc." While true for country roads, those above papers show that the same correlation can not be identified on city roads.
Now, what I know is only from this article, and it may be that the author cherry-picked the few papers which show that the 'reaction time' hypothesis is unsupported by the evidence. But "refute" means "to deny the accuracy or truth of", and certainly the article refuted that hypothesis.
And this is the problem. "Not statistically significant" means that the effect is very small. This is what you would expect if narrower lanes make driving more dangerous but then drivers compensate by being more careful; they approximately cancel each other out. The author is making much hay out of the possibility that drivers might be not only compensating but overcompensating for the reduction in safety, theoretically causing a (small) net increase in safety.
The fallacy of this is that intentional danger is not the only possible way to increase driver vigilance. As one example, we could promote self-driving cars. That allows us to capture a much larger safety increase because the increase doesn't have to be weighed down by the counterbalancing cost of having narrower lanes and less room to maneuver.
You use the phrase "intentional danger". The flip side is that "illusory safety." A 12' lane may feel safer even though it actually isn't. But it feels like you stress the "intentional danger" part when the label is irrelevant - the questions are the number and severity of crashes, of human injury, of overall traffic capacity, etc. How one labels the emotional aspect of the driver's internal state isn't relevant to the outcomes.
Also, as secabeen pointed out, driver vigilance isn't the only concern. To add another one 12' of road surface is simply more expensive to repair, clean, and replace than 10' of surface.
Regarding self-driving cars - sure, but how does that change anything in the next 10-20 years of road design? The underlying factors won't change unless a large percentage of vehicles are self-driving. You might as well argue that enforcing a 10mph speed limit would be safer as well, as another example of a solution which, even though correct should it occur, won't affect anyone's planning now.
(You can also see something similar with internet bandwidth. Same principle, I think.)
There's a Wikipedia article about the theory that narrower, signage-free roads are safer on aggregate: http://en.wikipedia.org/wiki/Shared_space
(I don't know/care if these are useful to you - simply a brain dump, as you asked)
So you buy another server. Now you have 2000 users, but once again it is starting to run slowly.
You decide to stop there. Clearly, more servers wont help. You'd just get more and more users.
You buy a second server. Now, your server still is overloaded between 08:00 and 9:00 but fewer people use it between 07:00 and 08:00 and 09:00 and 10:00.
There are plenty of people avoiding the main traffic times for whom the annoyance of congestion is just a tiny bit larger than the annoyance of leaving home an hour earlier. Take away a bit of congestion and they move their schedule.
Your analogy is broken because building more servers doesn't "get more users". You have to service a fixed number of users in the most efficient manner possible. Providing a car lane for each of them is not efficient.
So I open another stall next to it but the lines don't seem to get much shorter even though I'm making twice as much coffee.
Notice that nowhere in there was a requirement that said infrastructure pays for itself. More often than not, and especially in small towns, it doesn't.
But don't believe me, take it from a civil engineer and urban planner who has done a lot of real research into this phenomenon: https://www.youtube.com/watch?v=tn7aJ_Ti-co
You're assuming that having more roads makes it more efficient, but that's not necessarily true. If having less urban roads convinces more people to use mass transit, for example, it might be more efficient.
Article provides very little useful information. Again, it's obvious that if you expand one road in a congested city then it will get full of cars again, because it takes the overflow from all of the other congested roads. And if you reduce congestion in general then people might choose to drive more often.
But this does not persist as a 1:1 relationship. China has proved as much by building a bunch of empty highways and cities, as is also demonstrated by urban highways carrying more traffic than rural highways with the same number of lanes. The "problem" is that if you have a lot of congested highways then you need to add a lot of lanes before you'll hit saturation, but that hardly proves that it can't be done. The observed 1:1 relationship in some locations is easily explained as a result of widespread insufficient infrastructure investment, resulting in roads with insufficient capacity even after the expansion.
He was drawing an analogy to the 'swing-top' bin - how you always try to fit more in and never empty it. "What would be the state of affairs a week from now if I gave you all a brand new swing-top bin to put next to your current one?"
http://i.imgur.com/DKRsGZ4.png
It was on an episode of Top Gear. It's typically empty, and in the above image you have government officials going to work.
How to Live Dangerously by Warwick Cairns is a great book on the topic as well.
I'm not disputing the idea that people might respond to perceived safety by taking more risks or vice versa. It's almost a corollary to the efficient market hypothesis. However, that doesn't tell you anything about whether they will overcompensate or undercompensate in any given context.
And what I'm really objecting to is the idea that we should make people "feel" less safe by doing things that actually make them less safe if not for people [over]compensating for them. Because that's a very dangerous game if you're wrong and it's completely ignoring the possibility of solving the problem in other ways, which should on balance be more effective because you aren't running the wrong way with the ball.
A quick glance at Wikipedia found this reference: http://link.springer.com/article/10.1007%2FBF00166218 which appears to be a decent summary.
Let's see a cite to that data, because it seems ridiculous. Obviously if you make a road less congested people may start preferring it to other, more congested roads, but that just means the reduction in congestion is distributed rather than concentrated, and how is that a bad thing?
The entire premise of this article is questionable. The theory is that people will drive more carefully when the roads are more dangerous. From this the argument is that we should make the roads more dangerous in order to make them safer. This is obviously completely counterintuitive so they point to some evidence that it could be true (which itself seems to imply that its veracity lies near the statistical margin of error). The real problem is that it's a false dichotomy. Making the roads more dangerous is not the only way to make people drive more carefully. And alternative ways of encouraging people to drive more carefully are obviously preferable to a method that, at a given speed and level of care, is more dangerous according to the laws of physics.
More than that, this “make the roads dangerous to make them safe” is completely backwards when we're on the verge of commercially available self-driving cars. A self-driving car is obviously not bound by human psychology, so for all of those vehicles, making the roads more dangerous will only make the roads more dangerous.