"jariten1781" (jariten1781)
11/25/2015 at 10:30 • Filed to: None
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"jariten1781" (jariten1781)
11/25/2015 at 10:30 • Filed to: None | 3
| 10 |
So, saw this line in the Gizmodo piece about traffic tunnels or whatever (couldn’t finish the article because whenever I see this my vision goes red.)
So, how can something so unintuitive be true? Short answer: it’s not and while the study used those words, it’s with a specific definition of ‘congestion’ they selected. This misinterpretation has been going around since the initial study a number of years ago.
How would you define ‘congestion’?
1) Time spent in traffic at less than the speed limit?
2) Number of cars passing through a choke point?
3) Miles traveled?
If you answered 3, then you already can understand the study’s results so stop reading and go buy a turkey or something.
It’s not how your average shmoe would define congestion, but that’s how the leads chose to define it (and, to their credit, they’re extremely clear about it throughout the paper...the media did not pick up on that though).
Here’s what the study actually found: when roads are widened or new roads were added, traffic became freer flowing and people adjusted and more folks traveled, individuals more often, or people drove further. Perfectly intuitive. Because ‘miles traveled’ increased commiserate with added miles of lanes, by their definition, ‘congestion’ increased. By most other definitions it would be static or have decreased.
It’s also interesting to note that, while Mass Transit zealots have latched onto the misinterpretation, the study is also very clear on another point: Increases in Mass Transit have no significant effect on ‘congestion’ (aka miles traveled in their parlance).
Couple other things to note about the study: It was done by economists so you need to read it through that style of lens, it is only valid for interstate highways (though they assert it might be applicable to other urban roads but they admit they don’t have the data set), and their final conclusion was that the only thing that directly reduced overall miles traveled in urban environments was large tolls.
I haven’t read it since it was first published, but here’s a link if you want to peruse and tell me how badly I misremembered and interpreted it: !!!error: Indecipherable SUB-paragraph formatting!!!
Ash78, voting early and often
> jariten1781
11/25/2015 at 10:35 |
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Interesting! I had always heard (and sometimes repeated) the idea that adding lanes doesn’t reduce traffic...and in many cases, it doesn’t. People tend to travel more when they perceive there to be better infrastructure and less traffic hassle.
IMHO, that’s a win unless you’re a hardcore greenie. But even from that perspective, assuming we all have a destination in mind, it’s much better to have cars traveling freely at 60mph than stop&go at 0-30mph in true “congestion.”
Aaron M - MasoFiST
> jariten1781
11/25/2015 at 10:37 |
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You’re right only if all roads are increased in size proportionally. Otherwise, the increase in flow makes congestion and backup more severe at other points in the roadway where the throughput declines. Generally speaking, large highway construction projects make congestion significantly worse at their exits into smaller streets, and that congestion backs up into the highway making travel no faster than before. Case in point: Boston’s Big Dig project. So yes, highway lane expansions do tend to make traffic worse.
Also, while mass transit has little impact on vehicle miles traveled, it has a significant impact on average commute times. The road improvement that has the biggest impact on both? Bike lanes.
wiffleballtony
> jariten1781
11/25/2015 at 10:48 |
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Whenever I see an Alyssa Walker article shared to Jalopnik, I have a colorful verbal reaction. Honestly, those people see anything that gets in the way of them bicycling on their vintage Schwinn to their local artisanal bakery in their downtown urban bistro district as evil. Neverending the people who have to work at a real job or have an actual family.
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wiffleballtony
> Aaron M - MasoFiST
11/25/2015 at 10:54 |
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I wouldn’t use anything in Boston as an example especially the Big Dig.
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Aaron M - MasoFiST
> wiffleballtony
11/25/2015 at 10:59 |
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Heh, point taken. Still, it’s a clear story: bigger 93 tunnel opens, traffic through tunnel itself quicker initially, more congestion around literally every exit, now it takes 30 minutes to get through a mile-long tunnel. And the reason Boston is a good example for this is that the city is growing at a fairly modest pace, so the degree of congestion can’t be caused by population growth alone.
davedave1111
> jariten1781
11/25/2015 at 11:01 |
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The whole thing’s just a load of nonsense, both the arguments for and against. It’s no more true that mass transit has no effect than that road capacity is irrelevant. People (conveniently) like to forget that we don’t build new transport infrastructure where there is no demand - in fact, we build it specifically to cater to demand - so it’s hardly surprising that new capacity gets used.
Arguably, all any of those studies show is that when we need more transport capacity, we never build enough.
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jariten1781
> Aaron M - MasoFiST
11/25/2015 at 11:10 |
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Wasn’t really attempting to assert anything directly, just giving context to the only study I’ve seen cited (if they bother to cite anything with actual data) when people say ‘congestion is increased by more traffic lanes’.
Boston Big Dig isn’t something I’ve looked into in probably 7 or 8 years but last I saw the state funded study was saying significant savings in time and studies by anti-automobile folks were saying ‘not worse nor better, just a waste of money’. I’m only up there a couple times a year and I cab then walk so I can’t speak intelligently on who’s right.
Anyhow, individual case studies aren’t particularly relevant to making a general assertion.
As to bike lanes, I’m totally ignorant of their effects...never plowed through the data...but I doubt they’d move the needle on these guys study since it only covered interstates, probably have an identical effect to Mass Transit (ie no change) would be my gut feeling. I’ll happily read through some research when I’ve got some free time if you have some good sources. I find the whole mess fascinating.
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jariten1781
> davedave1111
11/25/2015 at 11:18 |
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The whole thing’s just a load of nonsense, both the arguments for and against. It’s no more true that mass transit has no effect than that road capacity is irrelevant.
Yep, totally agree. My intent, I suppose, was to remind that when something seems unintuitive you should really go look at what the actual authors were stating rather than what some blogger/paper is interpreting.
“More lanes make congestion worse” is a crazy statement that’s easily parroted while the actual result of “When traveling is easier more people do it” is kind of ‘duh’.
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davedave1111
> jariten1781
11/25/2015 at 11:37 |
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It’s also a lesson in clearly defining your terms, and looking at the whole picture. A road does not exist in isolation, and treating it as if it does gives entirely opposite results to treating it as the part of a holistic system that it actually is.
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Aaron M - MasoFiST
> jariten1781
11/25/2015 at 12:38 |
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The study here makes more sense as what it is stated in the abstract: a quantitative proof of the Downs-Thomson paradox.
https://en.wikipedia.org/wiki/Downs%E2%…
There’s about forty years of economic study around this idea that traffic increases proportionately to capacity, both in highways and more generally.
https://en.wikipedia.org/wiki/Braess%27…