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Speaker 1: Gold. It's Jonesy Demanda driving you home. Friday is a

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Speaker 1: great day for science information. For those that don't know,

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Speaker 1: Amanda used to helm a science shell. I guess you

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Speaker 1: didn't really helmet. You were there with a bunch of

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Speaker 1: other people wearing matching knits and had reasonable haircuts.

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Speaker 2: Now we had knits in our hair, but you know

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Speaker 2: how we have tint Tuesday. Maybe we should do strap

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Speaker 2: on your shoulder pads for a science watch Friday.

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Speaker 1: Okay, why don't we do?

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Speaker 3: That's science?

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Speaker 1: I can do more if you like what have we

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Speaker 1: got today?

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Speaker 2: Let me tell you this. I'm a big fan of

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Speaker 2: a woman called Hannah Fry. She's on an English or

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Speaker 2: she's on a podcast called The Rest is Science, and

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Speaker 2: she has just described something called a phantom jam.

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Speaker 3: You know, when you're in.

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Speaker 2: Traffic and suddenly you come up and think, oh god,

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Speaker 2: the traffics that are standstill. There must be a big

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Speaker 2: accident up to front. And then you finally crawl along

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Speaker 2: and you get to a point where all the traffic

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Speaker 2: is flowing freely, but there's been no accident. Why did

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Speaker 2: we all stop? What happened there? It's called a phantom jam,

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Speaker 2: and this is what's happening, Because when a motorway gets

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Speaker 2: too crowded, people apparently stop behaving like individual cars, and

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Speaker 2: the entire motorway behaves according to the rules of fluid dynamics.

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Speaker 2: Here's what happens. When the traffic is dense. The cars

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Speaker 2: are driving quite close to each other, and maybe at

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Speaker 2: some point somebody changes lanes or taps their brakes a

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Speaker 2: little bit too hard, but that makes the person behind

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Speaker 2: them have to break, and that means a person behind

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Speaker 2: them has to break, and so on. And because of

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Speaker 2: human reaction times in different times that we all react,

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Speaker 2: the amount of breaking increases as you go further back,

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Speaker 2: until about twenty cars or so back, the amplification is

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Speaker 2: so big that the traffic comes to a standstill. Yeah,

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Speaker 2: so you have set off an unstoppable force. And this

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Speaker 2: is known as a phantom jam. So you're not driving

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Speaker 2: towards a phantom jam. The traffic jam is a wave,

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Speaker 2: and it's come through you and goes past you right

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Speaker 2: like a Mexican wave, like a Mexican wave, And so

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Speaker 2: there's no point in getting anxious about it. This is

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Speaker 2: what Hannah says. There's only two things we can do,

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Speaker 2: and one of these isn't likely. One is that we

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Speaker 2: all get driverless cars because the better reaction times would

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Speaker 2: stop this kind of phantom wave occurring. Or this is interesting,

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Speaker 2: stop tailgating because that's what makes people tap their brakes

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Speaker 2: or instantly have to change lanes at the last minute.

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Speaker 2: That's what creates the beginning of the chaos. And once

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Speaker 2: that happens, as we know now, that phantom wave is

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Speaker 2: going to come through, a ghost wave roll over you

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Speaker 2: and there's nothing you can do. So if you're in

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Speaker 2: traffic and you can't see any sign of accent, head

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Speaker 2: and don't get cranky, let it roll through, take a

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Speaker 2: deep breath and you'll be on your way before too.

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Speaker 1: Or option three by a motorcycle and you look cool too.

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Speaker 3: There's always that this is being I may have we

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Speaker 3: sitting any want to speed records, certainly having fun. Once

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Speaker 3: science rapping sig