cars and how they get that way

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Andrew
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Re: cars and how they get that way

Post by Andrew » 03 Aug 2018, 13:19

Phoenix uses lots of ramp metering. I'm not sure how much it helps.
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Highway
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Re: cars and how they get that way

Post by Highway » 03 Aug 2018, 14:56

Andrew wrote:Phoenix uses lots of ramp metering. I'm not sure how much it helps.
It's been shown to be at least effective at increasing speeds and decreasing travel time, and reducing the amount of perceived congestion. If the highways are empty, it's not going to have much effect, but it will help delay when they get clogged up.
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lunchstealer
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Re: cars and how they get that way

Post by lunchstealer » 03 Aug 2018, 15:19

Denver is also all ate up with congestion-dependent ramp metering.
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tr0g
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Re: cars and how they get that way

Post by tr0g » 03 Aug 2018, 15:44

There's a lot of it in Houston.
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Jennifer
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Re: cars and how they get that way

Post by Jennifer » 04 Aug 2018, 01:04

Ellie wrote:
03 Aug 2018, 10:32
Mo wrote:
03 Aug 2018, 05:10
Jennifer wrote: In Atlanta and its surrounding suburbs, some of the highway on-ramps have actual traffic lights, presumably powered by under-road car-detecting sensors. The lights are not always in use, but when they are, only one car is allowed per green light. I'd never seen that before coming to Atlanta.
California has those. They generally are activated during times of high congestion.
That's so interesting to me -- they're everywhere in the Twin Cities, and it never occurred to me they weren't used everywhere in the country.
The weird thing is that, while Atlanta is certainly far bigger/more densely populated than anyplace I've lived before, I've driven into New York and Boston more times than I can count, and never saw them there either.
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Warren
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Re: cars and how they get that way

Post by Warren » 04 Aug 2018, 14:48

Highway wrote:
03 Aug 2018, 11:41
There is a huge Not-Invented-Here attitude within highway organizations. They almost need to be convinced they came up with an idea on their own. It's almost worse if it's something that is effective other places, because it's like they "lost" or something.
But ramp metering is such a horrible idea that you wouldn't even think of doing it unless you could blame it on someone else.
Highway wrote:
03 Aug 2018, 11:41
Ramp metering is also one of those last resort kind of things when you can't construct your way out of a problem.
This is what I'm sayin.
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Highway
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Re: cars and how they get that way

Post by Highway » 04 Aug 2018, 16:58

I have no idea why you think it's a horrible idea. It's a safety improvement, it's a throughput improvement, it's a congestion improvement. It improves all those things with hardly any operational downside. There are reports of long waits to get on at particular ramps, but newer operations work harder to keep this from happening. For instance, MnDOT targets a wait of no more than 4 minutes to get onto a ramp from a surface street, and the congestion that would occur if the metering wasn't there would usually cause a lot more wasted time. The only thing is that it requires 1) enough storage at the entrance and 2) additional infrastructure and maintenance.
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Kolohe
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Re: cars and how they get that way

Post by Kolohe » 04 Aug 2018, 16:59

I'll take your word for it as a professional. I think they're all kinds of useless if not outright counterproductive.
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Highway
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Re: cars and how they get that way

Post by Highway » 04 Aug 2018, 17:07

Kolohe wrote:
04 Aug 2018, 16:59
I'll take your word for it as a professional. I think they're all kinds of useless if not outright counterproductive.
The thing is, you can't really see the effect. It's one of those "can you prove a negative" things. If it's delaying the onset of significant congestion by 15 minutes on the days when it's really bad, you're not really going to notice that it happens, but it's still providing a significant boost against lost time. If it reduces the number of days that there is a traffic jam from 60 days per year to 40 days per year, then again it's not really something that people are noticing. A frequent question about them is "Why am I being stopped on the ramp when traffic on the freeway is flowing at normal speed?" Because people just don't understand the point of the operation. It really isn't to limit the number of cars on the freeway. It's to address a single problem that most people just don't recognize: the traffic jam that starts at the ramp merge and then propagates away from there.
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lunchstealer
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Re: cars and how they get that way

Post by lunchstealer » 04 Aug 2018, 18:38

I will say that at metered onramps I almost never have to worry about the dumbass in front of me not accelerating enough to merge properly. I almost always have plenty of room to match speed, even at poorly built, too-short onramps. That's just my observation.
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Jadagul
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Re: cars and how they get that way

Post by Jadagul » 04 Aug 2018, 19:57

Traffic flow has these really extreme tipping point effects where a minor disturbance in one place can propagate and jam up large swaths of road. This guy has some really good writing about it. Dense traffic is like a supersaturated solution: it might be stable on its own, but add in a crystallization seed and the whole thing changes phase. (As I understand it---though Highway is the expert---this is also why you basically never see smoothly flowing traffic at 30mph. Once you get below 40-ish, things are too unstable and any super minor disturbance will amplify into a jam).

Metered onramps prevent some of those disturbances. So they have a lot of effects even if you can't see them.

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Andrew
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Re: cars and how they get that way

Post by Andrew » 06 Aug 2018, 20:07

I wish I could do unpleasant things to the team that designed the "safety" features in the Subaru Legacy. It is not possible to drive in traffic without all sorts of warning lights, incessant beeps, and the occasional braking from the car. I was a more dangerous driver than in my regular vehicle since I was regularly distracted and/or shouting at the car.
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lunchstealer
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Re: cars and how they get that way

Post by lunchstealer » 07 Aug 2018, 04:10

Is it just me or is Toyota Flo totally a cylon?
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Warren
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Re: cars and how they get that way

Post by Warren » 07 Aug 2018, 15:57

lunchstealer wrote:
07 Aug 2018, 04:10
Is it just me or is Toyota Flo totally a cylon?
Are you crossing the streams?
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lunchstealer
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Re: cars and how they get that way

Post by lunchstealer » 07 Aug 2018, 16:22

Warren wrote:
07 Aug 2018, 15:57
lunchstealer wrote:
07 Aug 2018, 04:10
Is it just me or is Toyota Flo totally a cylon?
Are you crossing the streams?
I keep getting online Toyota ads, and they've got a ... presenter woman? Not sure what the term is, but basically a Flo From Progressive but for Toyota, and ... maybe it's just me but I'm pretty sure she's a cylon.

It's really just me isn't it.
"The constitution is more of a BDSM agreement with a safe word." - Sandy

"Neoliberalism. Austerity. Booga booga!!!!" - JasonL

"We can't confirm rumors that Lynndie England is in the running to be Gina Haspel's personal aide." - DAR

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Kwix
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Re: cars and how they get that way

Post by Kwix » 07 Aug 2018, 16:25

lunchstealer wrote:
07 Aug 2018, 16:22
Warren wrote:
07 Aug 2018, 15:57
lunchstealer wrote:
07 Aug 2018, 04:10
Is it just me or is Toyota Flo totally a cylon?
Are you crossing the streams?
I keep getting online Toyota ads, and they've got a ... presenter woman? Not sure what the term is, but basically a Flo From Progressive but for Toyota, and ... maybe it's just me but I'm pretty sure she's a cylon.

It's really just me isn't it.
Her name is Jan and yes it's just you.
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