> as state DOTs widen highways to reduce congestion, in complete ignorance of all the data proving that new lanes will be clogged by the new drivers that they invite.
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.
The phenomenon of adding lanes not reducing congestion is generally a reference to the "Downs-Thomson Paradox"(http://en.wikipedia.org/wiki/Downs–Thomson_paradox) or "Triple Convergence" related research.
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.
The Downs-Thomson Paradox makes reasonable sense, but it doesn't prove the claim from the article. It explains how adding road capacity could make traffic congestion worse (if it causes the preexisting level of mass transit availability to become unsustainable), but not why it inevitably must. For example, if mass transit in a particular city is already useless and disused then that can't happen. It also points to a way out of the paradox: Expand road capacity and subsidize mass transit availability at the same time.
That isn't a reality due to the massive cost of either options (basically, pick one). Successful mass transit using the roads (eg bus rapid transit) require taking capacity out of the highways and therefore aren't mutually compatible.
I had not heard of the Downs-Thomson Paradox, thank you very much for sharing it.
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.
Downs-Thomson contains its own ad-absurdum refutation. If adding capacity makes congestion worse, then why can't we make congestion better by reducing capacity? Clearly this is wrong in the general case.
It does not state that it makes it worse, it states that it does not improve it. i.e. that there is an approximate equilibrium that is reached regardless of road capacity in an environment where there is more potential traffic capacity for congested times than the roads could realistically be made to accommodate.
What such simplistic studies miss, though, is the reason why those drivers are out there in the first place. They are going to and from different places, doing different things at different times. By treating traffic as a variable to be optimized in a vacuum, the academic and professional urban planners tend to miss the forest for the trees.
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?
I think it's a three-part problem. One, it is a flow problem, and by removing congestion at one bottleneck you mostly deliver traffic more efficiently to the next bottleneck. Actually increasing traffic flow is much more expensive than the cost of any single project. Second, over time, you end up with induced demand -- if you actually do get rid of all the congestion, longer commutes will become more practical, and traffic will increase until the marginal-next-commuter is discouraged from adding his car to the scrum.
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).
One explanation could be that people are lazy and will generally opt for the conveniences a car if the perceived disadvantages are relatively small. I and many people I know probably would consider a car if we lived in a city optimized for that.
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.
The theory is that people will drive more carefully if they perceive the roadway to be more dangerous. That is not the same as it actually being more dangerous.
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.
> The theory is that people will drive more carefully if they perceive the roadway to be more dangerous. That is not the same as it actually being more dangerous.
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.
> making the lanes narrower does make it actually more dangerous.
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."
That's not a refutation, it's a contradiction. The evidence offered is not sufficient to actually prove the assertions. In particular, those crash frequencies need to be normalized against the reduced capacity in order to be a meaningful comparison. If narrowing the road decreases crashes because fewer people are using the road, you don't have a safer road, just less road, and you may have merely shifted the crashes to alternative routes. On the other hand, if narrowing the lanes makes people drive more carefully without significantly constricting flow, that's a real result that deserves to be stated clearly.
I chose my words carefully. The quote in the article is in turn a quote from http://trb.metapress.com/content/x7854w1160551331/ . The article links to that publication. The abstract of that publication says:
> 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 "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."
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.
As a quibble, "not statistically significant" means "cannot tell if there was an effect, either positive or negative, because it's smaller than the noise." The only difference is that one can't use it to argue that it 'theoretically [caused] a (small) net increase in safety'.
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.
Right, but you're missing the author's point. Smaller lanes make the space feel more human-scale and friendly to pedestrians and bikers. Traffic engineers argue that larger lanes are safer. These studies show there is no evidence of that. Given that smaller lanes are more appealing, and have no measurable impact on safety, the trend towards larger lanes should be reversed, and smaller lanes implemented on new roads.
Imagine if you have an IT company with a server. Your server can handle 1000 concurrent users. It is running slowly because a lot of people try to access it.
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 have 1000 users and a server that can easily do the work 20000 users want it to do each day. Yet, every weekday between 08:00 and 9:00, your server is overloaded.
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.
Cities have relatively fixed populations. The problem is not allowing everyone to drive their own car: that's stupid. The problem is how to persuade more people to catch the bus/train. Building roads doesn't make anyone's life any easier or better because it just persuades people to drive instead of catching public transport. Less roads actually helps because public transport gets better.
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.
We all know that roads aren't free. If they weren't worth building in terms of increased economic output, however, then city planners would stop building them.
That seems reasonable on its face. The reality is that state and federal funding hinges on city planners padding budgets and increasing capacity to meet future growth. Meanwhile, cities and towns put themselves in hock to meet the servicing demands of their infrastructure, requiring more state and federal funding, requiring new projects with padded budgets and increased capacity.
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.
You say that as though you think there isn't a significant economic benefit to having a more efficient transportation network. Having higher-capacity roads is beneficial even if they aren't toll roads.
You say that as though you think there isn't a significant economic benefit to having a more efficient transportation network
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.
> There was an article about people's tendency to soak up additional road space posted on HN fairly recently
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.
I had a recording of Ben Elton's standup in the mid-1980s in the UK, and he raised the issue of adding lanes to clogged roads just inviting more traffic, leaving the road just as clogged as before.
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?"
> There's actually a ton of data to support the idea that making activities feel more dangerous makes them safer.
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.
I had the impression (from talking to traffic engineers) that it was pretty much common knowledge in the field that newly constructed highways only alleviate congestion for a very short time (a year or two), after which it returns to previous levels on both the old and new routes.
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.