英語語言學(xué)習(xí)：人們選擇的交通方式

Hello Antony Funnell here, and welcome to Future Tense. Like many people I know, I catch the bus to work.

And this is my stop, one sec...

Thank-you!

Okay, come this way while I talk.

Travelling on the bus is pretty straightforward. But getting from this stop to my work, which is only a few minutes away, is far from direct. For a start, the stop is really on the wrong side of the road and so I have to use an overpass which mean going up two sets of stairs, turning hard left, then going down another set of stairs, veering left again and then two more stairs, before I turn hard right down to the next set of stairs, then hard left, 50 metres walk and then hard right again, another 50 metres or so, and then I'm there. And at the end of the day, going back to the bus stop, I have to use a tunnel.

It's all good exercise, of course, but it's poorly planned, because the bus station, the roads, the buildings, everything in this area of my city has been developed in an ad-hoc manner. And so navigating the short distance from the bus stop to my work is more like managing an obstacle-path rather than a streamlined thoroughfare. So why does it have to be so difficult?

Left to our own devices we don't usually walk in rigid straight lines or make 90-degree turns, so why do so many architects and urban planners still favour grids and sharp angles?

In today's program we'll meet several people involved in seeking a better understanding of the way humans move, both on foot and in cars. We'll find out about 'spatial economics', and the importance of 'time-to-collision', and we'll meet the US physicist who came up with an optimal method for boarding an aircraft.

Jason Steffen: My name is Jason Steffen, I am the Lindheimer Fellow at Northwestern University in astrophysics. What this process basically does is it turns a serial process where one person at a time sits down in the aeroplane, to a parallel process where several people sit down at the same time. The typical cost per minute for an aeroplane sitting at the gate is about $30, between $30 and upwards of a few hundred dollars or even $1,000, depending upon the airport. And so every minute that it's sitting there, it is not making money. When you take into account the number of flights a day and the number of aeroplanes that you have in your fleet, it could be tens or hundreds of millions of dollars a year.

Antony Funnell: That's not to be sneezed at.

Jason developed his optimal method for boarding back in around 2008, and later in the program we'll find out what sort of difference his findings have made to the airline industry.

But let's head back to the mean streets and pavements of the city and to Martin Butterworth from the organisation Space Syntax Australia, and the notion of spatial economics. Martin argues what's most important in designing urban areas is not to prescribe the way in which people and traffic should flow, but to actually look at natural patterns of movement and to mimic or enhance them. And the reason why is very simple.

Martin Butterworth: Because if it's easy to get to and around, people will use it. So when we look at places like Trafalgar Square in London, for 160 years lots of tourists came to Trafalgar Square, but Londoners weren't using it up until about 2003. So what we did was analyse the space, find out what people were actually doing, use our spatial modelling, correlate the empirical data of what people were doing with the model, and then forecasting a 1,300% increase if we put a new staircase in. So on day one, it worked. Not like, say, Darling Harbour in Sydney, a major project that's meant to deal with people, and for 25 years now it is still promising economic performance and social cohesion, and it's not delivering.

Antony Funnell: Now, that doesn't sound like brain surgery. Why is it so difficult for our urban planners to make these simple changes, to see what is, in a sense, obvious or should be obvious?

Martin Butterworth: The problem that occurs in urban design, as with a lot of design of cities, whether it's transport urban design, architectural planning, is that we've got this notion that has become ideologically bound and we can't really discuss it very creatively and interestingly, and that is if you have a building and another building, we want to know how people move between the two attractions.

What we show in cities is that it's not one or two buildings or attractions, it's the myriad of them, the multitudinousness of them. And so the way in which you get to them all is the street system, and if you will make the street system simple and easy and accessible for people to move, whether they are in vehicles or on buses or in delivery vehicles or on foot, then you are starting to get an understanding of how systems trade.

And it's the trading and economic performance that is also social cohesion of the same time, because if you have a number of people in a street and it's trading well, then people will bump into each other and they make it a cohesive local community. So what's happening is the big areas of transport on one hand, and planning, which includes design on the other, both of them are missing the point because they are looking at only one part of the system, simple attraction of the objects. So we are making places that are pretty and expensive and they don't work.

Antony Funnell: So the spatial economics/spatial syntax idea is that city design and functionality works best when it follows natural pedestrian flows, but that's not the way most of our urban spaces are designed.

In most of our cities developers are allowed to build siloes, be they for work or shopping or residential living or even for outdoor activity. And then transport authorities are engaged to build connections between them. And so as the number of independent siloes increase in an urban area along with the population, well, then you get gridlock.

Here's another way to visualise it. Think of the number of parks you've been to where people simply ignore the concrete or bitumen pathways that city authorities and architects have designed, and choose instead to make their own more human, more natural paths across the park.

Martin Butterworth: We look at cities across the planet in all cultures. And you'll get different ones in Europe and Asia and South America and the Middle East. The spatial layout is never a perfect grid in any circumstance that we've found anywhere on the planet, and we've been doing this for 25 years, so we are reasonably sure of our accuracy of the empirical data.

But in the city of London or in other cities that are in a different arrangement where we call them deformed grids, if you like, there there are other rules occurring which allows people to get through the space. So in the city of London itself it's something like a spoke with wheels, with a wheel around it. So these spokes are the major routes, and in between are all these little laneways. But if you go from one spoke to the next spoke, it's only three changes of direction. So if you know that you can finally understand the system.

So what we need to look at in cities is a multitudinous way of having spatial signatures that do naturally occur in various cities and then try to actually understand how we can measure them and then make forecasts that are real.

Antony Funnell: So understanding the natural flow of people within an environment is important in trying to make our urban spaces more fluid and connective. But it also helps, according to Minnesota-based Stephen Guy, to understand the instinctive way in which people move within a crowd.

Stephen Guy: The whole idea that you could simulate crowds is a new, exciting thing that took a while to gain hold. So the very first simulations were very simple. The original idea was let's just take the way people simulate particles or simulate planets and let's try that with crowds. We are going to adopt the forces, we are going to try to treat the forces a little bit to be more like people than like particles or like planets, but the fundamental interaction mechanism was borrowed directly from other physical systems.

And anybody who is a human being knows that there are really important differences between people and particles or people and planets. One of the most important things is that we can anticipate the future. I have a brain, you have a brain. When we see each other coming, we know what's going to happen in the near future and you can use that to anticipate and overcome and avoid each other well before the actual physical…we get close to each other. And that's the thing that excited us about this project, just trying to understand and really capture what way that human-human interaction is different from anything else in the physics, how that particular effect of our brain can be captured mathematically.

Antony Funnell: Now, I should mention that Dr Guy is an Assistant Professor in the Department of Computer Science and Engineering at the University of Minnesota. And the actual research he and his colleagues have conducted into the way in which pedestrians move in a crowded environment without bumping into each other, has led to their theorising a universal mathematical law, which they call 'time-to-collision'

Stephen Guy: Yes, so the big thing that we wanted to do was really put aside a lot of the earlier hypotheses about what humans may or may not do and really focus on what's in the data. And something that's nice about living in the 21st century is there's lots of data. There is lots of advances; thanks to surveillance cameras, thanks to advances in computer vision we can get hundreds and hundreds of trajectories of people walking in different kinds of environments.

So we had data from previous researchers who studied people in the bottlenecks, people on college campuses, people just outside of shopping walls, and what we can see is we have lots of trajectories, lots of paths that these people are taking, and we took for patterns in these paths, patterns in the trajectories.

Let me go back again to planets. If you think about when two planets interact, what Newton tells us is that the force between the two planets is related to their distance. If they are very close they feel a strong gravitational force, and if they follow it far away they feel less gravitational force. With humans, rather than distance affecting our forces, what we found is that it's time-to-collision. If two people are going to collide very imminently, if they are going to run into each other within the next half a second, within the next one second, you feel really strong discomfort from that interaction, whereas if they are not going to interact with you at all, if they are walking close to you but in the opposite direction, there's almost no effect of them on your path. If we look at the data we can see that really people ignore the distances and react almost subconsciously to how imminent collisions are. So that's what time-to-collision is, it's if I look at somebody, if I estimate where I'm going right now and where they are going right now, how long until I interact with them.

Antony Funnell: So, just to be clear, as I'm walking along a road or I'm walking, say, through a pedestrian mall, there are people coming towards me, my brain is subconsciously making decisions all of the time about how far away people are from me and whether we are going to collide, and that anti-collision mechanism within my brain only kicks in when the chance of collision is less than I think you say three seconds. Is that correct?

Stephen Guy: Correct, yes, only if you think that somebody is going to be colliding with you within the next two or three seconds do you really do anything about it, otherwise you kind of filter everybody out who is not really in your way.

Antony Funnell: So our brains at any one time as we are walking along, as we are navigating, our brains are making multiple calculations about collision.

Stephen Guy: Exactly right. So if you think…what's kind of interesting is the ability to think about collisions is actually found all the way down at the insect level, evidence that there is some neurological mechanisms built into insects already that start to reason about time-to-collision. If you think about flying moths, you really need to be looking ahead, thinking ahead about what's going to happen several seconds into the future.

And it is all the more sophisticated when you have humans interacting with humans. And to me it's really interesting that I don't have to think about this consciously, it's not something that I'm actively making time-to-collision calculations, I don't break out my slide rule and try to figure out how long until I collide with something. It feels built-in, it is something that happens just as people are walking along, without having to make any sort of active thought about it.

Antony Funnell: And that's the basic theory. We've linked to supporting material on the Future Tense website.

So, 'time-to-collision' is interesting in helping us understand the dynamics of crowd movement, but how does it help us at a practical design level?

Stephen Guy: There are lots of models of crowd simulation, it's a field that goes back almost 20 years at this point. And what we want is not just models that feel good or models that look good, we want models that accurately reflect human emotion. And because this law is so consistent, because we've seen this law now in so many different datasets and so many different conditions, we can take existing simulation models and understand how well they are by seeing how accurately they reproduce this law. Do they really show the same dependency on time-to-collision that humans do? So that's probably one of the most important things, is that it allows us to evaluate existing methods and see which are better than others or which are worse than others.

Also because it's a nice, simple law, it automatically suggests a new way to simulate crowds, and that's something we discussed in our paper, is how to turn this law directly into simulation. And when you have more accurate simulations you are able to much better utilise your space, you are able to make buildings that have more effective hallways and more effective layouts of how people will flow, you're able to understand the kinds of safety and evacuation times in a better fashion, other than make general, overly conservative heuristics. So that's really where myself and I think a lot of researchers in the area are excited to go, is in a direction of making much better utilisation of our space. As we have more people sharing less space, understanding these movements better is going to allow us to have more efficient utilisation.

Antony Funnell: And I presume you would say that your time-to-collision law could at least help convince some of those governments, some of those civic authorities that there are better ways to plan, that there is a need to look more at the natural patterns of pedestrian movement within a city, take those into account.

Stephen Guy: That's definitely one of the most important things. If you can understand how people move better you can take this into account, and the more evidence you have the better job you can do of convincing the people who make the ultimate decision.

Antony Funnell: It's one thing to acknowledge that urban spaces don't always allow for the fluid movement of people, both pedestrians and drivers. The underlying premise of this program is that there's much that doesn't work.

But it's important to also recognise that there are many technological systems already being deployed to try and make the best of the heritage infrastructure we have—the highways and main roads, for example—that are not going to disappear anytime soon. And that's where Susan Harris comes in.

Susan is the CEO of a not-for-profit organisation called ITS Australia, ITS standing for Intelligent Transport Systems. ITS members include government agencies, transport businesses and academic institutions and their aim is to find and promote new technologies and approaches that can help streamline our traffic.

Susan Harris: The managed motorways are a newer option in Victoria and across Australia whereby we really aim to make sure that the traffic on the motorway is moving as efficiently as it can all the time. For example, there have been studies done and they have identified that the optimal speed at which you can get the most vehicles per hour through a certain length of motorway is around 80 kilometres an hour, that's when the traffic is congested. So if you are going faster than that you get a bigger gap between vehicles and you get less cars through per hour. If you are starting to get slower than that, well, you are just not getting the throughput through. So what we have in a number of our motorways now is drip-feeding of vehicles onto the motorway so that the motorway can stay at that optimal speed of 75 or 80 kilometres per hour, and that has been shown that that can improve the throughput on the motorway by something like 25%. So that's kind of the equivalent of an extra lane on your motorway.

Antony Funnell: And that drip-feeding is done by a coordinated lighting system, isn't it.

Susan Harris: Yes, so a lot of people just think that there is kind of a random number and it just lets you on slowly, but there is an amazing amount of algorithms and maths behind that, and it's managing the flow of traffic, not just at one point in the motorway but at various points right along the chain. So it looks at the motorway as a pipe and managing the traffic onto that motorway at the various points along the line. So it is looking at each car entering the motorway, what's the density of traffic at that point, and also correlating that with other activity at the other ramps, both further down and earlier on in the motorway.

So in Melbourne and across Australia we've managed to get some benefits from ramp metering that are unheard-of elsewhere in the world because of the complexity of these algorithms and the depth of analysis that goes into managing this flow of traffic onto the motorways.

Antony Funnell: We know that there's a lot of modelling that goes on with regard to traffic flow, but from what you are saying there, what's also important isn't just the modelling, it's also the monitoring that's going on of the traffic and adjusting towards that real-time data that's coming in.

Susan Harris: Yes, so that live management of the data, there are sensors in the roads that assess what the traffic density is and then it feeds it back into the algorithms and adjusts the flow of traffic accordingly. So it really is live management of the traffic to respond to the current needs.

Antony Funnell: And who's doing all of that controlling of these systems? Is it done by algorithms these days, or are there people almost like an air traffic controlling system?

Susan Harris: Yes, it's a combination, so it's a balance of automated solutions, people keeping a watchful eye, picking up anomalies, and we've got public road agencies managing roads, we've got private road owners managing roads. So there's a combination of activity to manage this behind the scenes.

Antony Funnell: So we've got these sorts of systems operating in many of our cities, obviously not all of our towns and cities, but where are we at in terms of the potential of management for our traffic flows?

Susan Harris: We've had some significant achievements in terms of our motorways. And then we look at our traffic light systems and where we are at in terms of that. Again, we've got some incredible systems in Australia with a technology developed in New South Wales that has been rolled out to traffic light systems around the globe where we are able to manage traffic on a network basis. So we don't have traffic lights just operating on their own or operating in a corridor, but they operate in an entire network.

We are the envy of many cities in the US, for example, where they have more managed on a particular corridor or a main arterial which doesn't take into account the feeder roads. And particularly when you look at our large cities, you need to manage the whole grid, and some of our systems are quite sophisticated in the way they manage that.

Antony Funnell: And how do they do that on that sort of level, when you are not just talking about a corridor but you're talking about a whole area, a whole region of a city?

Susan Harris: Again, it's quite interactive. Some of the systems that we have in place have traditionally been more a let's look at the cycle and let's establish it and then we'll have to come back and review it in a few more years. But we are on the verge again of a new wave of technology with cars able to talk to cars, so vehicle to vehicle communication, and vehicle to infrastructure communication. So if you can imagine a wireless device within your car that gives us awareness of…first of all it's broadcasting a message, it says this is where I'm headed, this is the speed I'm going, this is my projected path. It gives out like a heartbeat every 10 seconds. In between those heartbeats when it is sending out this message…sorry, 10 times a second, not every 10 seconds. It's receiving information from all the surrounding cars and potentially from traffic lights, that this is my phase and timing and I'm about to turn red or this is what's going on. So it gives the cars much greater opportunity to avoid accidents but also to potentially move in a much more coordinated fashion throughout the city than the loop-based system that we have for our traffic lights at the moment.

Antony Funnell: And again, we're talking about not just huge amounts of data, but we're talking about systems being put in place that will crunch that data and in real time.

Susan Harris: Yes, like big data is all the talk. No matter what industry you are in at the moment, everyone is talking big data. And we've got all this information now, so what do we do with it and how do we leverage it. So the simplest thing, I was thinking on my way in here this morning, I'm sitting at the traffic lights, I was waiting for the green light to go ahead, and there was a green arrow ahead of me and I could have easily taken the green arrow but I was in the wrong lane. Imagine if that traffic light had been able to notify my navigation system in advance, that the green arrow was going to go first and hence that was going to be the quicker route, that would enable me to move through the city in a more efficient manner.

Antony Funnell: We did a program on Future Tense not so long ago looking at the idea of the fully autonomous car. One of the messages that came out in that program was that…that was really a kind of an end dream, that in the meantime there would be lots of technologies developed that would help our systems as we move towards this ideal of a city of autonomous cars. From what you're saying that is what's happening, that is the approach that is going to be taken within our cities with regard to the use of technologies or the development of new technologies.

Susan Harris: The autonomous car is really exciting. So what we are seeing is the manufacturers are working quite aggressively towards that end game. They are very much embedding it in their safety technology in these days. So Volvo have come out with a vision that by 2020 no one will die in a Volvo car. If we have automated vehicles that can communicate with one another, so they are wirelessly connected, they can see not just the car in front but the car ahead and around the corner or over the crest. The research there is telling us that we can get up to 270% improvement in our traffic throughput on a given stretch of road. So what we are saying is we don't just want these automated robots driving around, but we want robots that can be connected and can move in a coordinated fashion to really leverage technology to get that benefit for our cities.

Antony Funnell: Susan Harris from ITS Australia. And incidentally, they're part of a much wider network, and next year Melbourne has been chosen to host the 23rd Intelligent Transport Systems World Congress.

Excerpt from Mythbusters: It's a frustrating constant of commercial airline travel: boarding the plane always seems to take longer than it should…

Antony Funnell: It's probably one of the worst ways to move passengers onto an aeroplane; you board them in blocks of seats starting at the very back of the plane and moving forward. We know it's one of the worst ways to board, because we've all experienced the frustrations involved when they do it; people caught in the aisle, stumbling over each other. And yet this is exactly how most major airlines around the world have traditionally moved their passengers onto their craft.

Astrophysicist Jason Steffen got so frustrated that a few years ago he set out to design a better system, an optimal method for moving people onto planes. And after quite a bit of modelling that's exactly what he achieved. It's now called the Steffen Method.

What the Steffen Method involves is actually quite simple, you basically stagger the boarding of passengers onto a plane using a seat numbering sequence that alternates between rows, and that ensures that people aren't bumping into each other in the aisle or caught having to wait for the person in front of them to hoist their luggage into the overhead locker.

Jason Steffen: What this process basically does is it turns a serial process where one person at a time sits down in the aeroplane, to a parallel process where several people sit down at the same time. The typical cost per minute for an aeroplane sitting at the gate is about $30, between $30 and upwards of a few hundred dollars or even $1,000, depending upon the airport. And so every minute that it's sitting there, it's not making money. When you take into account the number of flights a day and the number of aeroplanes that you have in your fleet, it could be tens or hundreds of millions of dollars a year. And my method was about twice as fast as the traditional back to front method.

Antony Funnell: So there are big potential savings for the airlines in using the Steffen Method, as well as a reduction in frustration for passengers. If you're still a little confused, go to the Future Tense website and you'll find a link to a demonstration video.

Jason published details of his optimal method in both the US Journal of Air Transport Management and the American Journal of Physics. And back in 2008 and again in 2011 it got quite a bit of international media coverage.

So the question of course is, given the virtues of his people-moving approach and given that the airline industry is a sector always in the hunt to find savings, the question is how many airlines have now adopted his method?

Jason Steffen: There hasn't been a whole lot of interest in the airline industry, at least directed towards me. I was contacted by Virgin America to briefly look into it, but that ultimately wasn't able to go anywhere. I think the main value that my study provides is knowing where the floor is. If we did everything as best as we could, how much time is there to be saved and how could we recuperate that?

Then the airline…an executive can say, well, here's how long it takes for us to board, if we can cut that in half it might cost us one bazillion dollars to make that change, which is too much. However, we could make a smaller change that captures some of the benefit and it would only cost half a bazillion dollars. And so I think it's most useful as a way to gauge how much room there is for improvement in someone's process.

Antony Funnell: Were you surprised though that you didn't have more interest from the airline industry?

Jason Steffen: I admit I was a bit surprised that I hadn't been contacted by anyone for several years. So I was a bit surprised but the airline industry and I don't always run in the same circles. So I know that they probably had some of their own people looking at my research and giving their own comments on it about what might be done or why it is right or why it's wrong, something like that. It turns out that it wasn't wrong though.

Antony Funnell: Astrophysicist Jason Steffen, with the somewhat deflating though probably necessary reminder that even the very best of forward-looking ideas sometimes fail to get lift. Think fondly of Jason the next time you're forced to elbow for space in the aisle.

Our other guests on Future Tense today were Susan Harris from ITS Australia, computer scientist Dr Stephen Guy, and Martin Butterworth from Space Syntax Australia.

Karin Zsivanovits was my co-producer. The sound engineer was Peter McMurray. I'm Antony Funnell, cheers!