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SPACESYNTAX  November 2009

SPACESYNTAX November 2009

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Subject:

Re: Svar: [SPACESYNTAX] predicting traffic flow

From:

Urban Lists Sust Urb <[log in to unmask]>

Reply-To:

[log in to unmask]

Date:

Wed, 18 Nov 2009 18:51:08 +1100

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (137 lines)

Dear Bin,

Thank you for your response. I think that I was not clear in what I  
was trying to convey. I was discussing a broad urban scale, seeing as  
your paper was examining the city of Gävle, at the larger scale.

If you take each person, or household, they have an activity sphere,  
which at X% confidence, they occupy. They move about this sphere from  
Core Origins to multiple destinations by a variety of modes of  
transport, walking being only one. If we take travel statistics as a  
guide, then walking will be a minority mode of choice. What we know  
from studies of cities across Europe, is that there is a pattern to  
these activities, which could most likely be reduced to an algorithm.  
The core origins are informed by human choices - living and working.  
Activitiy destinations outside of these are formed by our multiple  
life networks. Moving between these is defined by the available modal  
choices that that particular city offers as well as individual  
preferences for modal choice, as well as the network of the city.

While underlying street pattern may influence choice of route, origins  
and destinations are informed by outside choice aspects, which,  
subsequently the networks influence. This is what I was meaning by  
purposeful behavior. I apologise for my lack of clarity.

Kind regards
Peter


On 18/11/2009, at 5:13 AM, Bin Jiang wrote:

> Dear Peter,
>
> Thanks for your comments. My feedback to your questions is as follows:
>
> Urban Lists Sust Urb wrote:
>> I see what you say below in your response to Hans, but how do we  
>> translate the random generation to the purposeful use of a "world"  
>> network with destinations, where we are trying to understand the  
>> average overall purposeful behavior, as against average random  
>> behavior?
> Sorry I am not sure if I capture your point. I was saying mobility  
> patterns formed by purposive walkers and random walkers are the  
> same, because they both are shaped by the underlying street structure.
>>
>> Maybe. if there is a misunderstanding, it is because I am not an  
>> ABM modeler?
>>
>> Kind regards
>> Peter
>>
>> On 17/11/2009, at 9:13 PM, Bin Jiang wrote:
>>
>>> Many thanks Hans for the detailed comments, my feedback to which  
>>> is as follows:
>>> Skov-Petersen wrote:
>>>> Hi Bin,
>>>> A few comments/questions:
>>>> 1) Apparently you are using two sw products: ArcGIS (for G�vle)  
>>>> and NetLogo (for London). Ir is not clear to me how the two were  
>>>> applied. I would assume that NetLogo was used for the agent  
>>>> simulation while ArcGIS was used for network analysis (metrics),  
>>>> but as it reads boh programmes were used for both purposes (but  
>>>> in different regions). Can you clear me up?
>>> In the paper we just say a few words of the difference between the  
>>> two platforms. At the beginning, we put Gävle data in ArcGIS,  
>>> while London data in NetLogo. However, this is NOT essential. In  
>>> other words, to get the statistics there is no difference between  
>>> the two, but they do differ if visualization is concerned.  
>>> Obviously in this connection, NetLogo outperforms.
>>>> 2) Is the NetLogo model-code you used for agents interaction with  
>>>> the network publicly available?
>>> Yes.
>>>> 3) are your purposely agents (II) applying a 'shortest path'  
>>>> search towards their target?
>>> Yes, but shortest path can be computed in real time. It would  
>>> reduce the simulation speed significantly.
>>>> 4) Wouldn't you assume that the purposely agents (II) could be  
>>>> further 'improved' by taking the probability (i.e. the number of  
>>>> potential facilities) into account when selecting targets/ 
>>>> destinations as a probability weight 't application of a temporal  
>>>> dimension be considered. As it is, the simulation mimics the  
>>>> behaviour of taxies quite well (roaming short distance, any  
>>>> where, all during the day), but not the way e.g. home-work  
>>>> journeys will take place.
>>> Of course as long as one has all these locations of potential  
>>> facilities. In our experiments, the destinations are randomly  
>>> generated, and they are randomly distributed.
>>>> 5) One main finding - as I read it - is that ABM's are not  
>>>> required to simulate traffic flows (which is quite disappointing  
>>>> for an abm-modeler :-)).
>>> What do you mean by this point? We relied on ABM for simulating  
>>> traffic flows as you can see.
>>>> Nevertheless, your conclude that abm's provide us with new ways  
>>>> to study the rational behind human (spatial) behaviour, but do  
>>>> not further elaborate on this.
>>> My point here is that drawn from our experiments ABMs provide a  
>>> means to study human spatial behavior instead of observing from  
>>> the real world.
>>>> To me - and that is probably what you are saying - the thing is  
>>>> that the network (obviously) is the mandatory, bounding condition  
>>>> for transport behaviour. It is interesting (and efficient) to  
>>>> come up with indicators (metrics) that can predict human  
>>>> behaviour patterns (at a gross level), but that we need the agent- 
>>>> based approach to further enhance our behavioural understanding,  
>>>> especially when considering behaviour beyond the 'average being'.  
>>>> Right?
>>> No, this is not what I intended to say. Also see above point. My  
>>> focus is understand average being rather than individual being.
>>>
>>> Cheers.
>>>
>>> Bin
>>>> Hans
>>>>
>>>>
>>>> >>> Bin Jiang <[log in to unmask]> 11-06-2008 17:00 >>>
>>>> Hi, this paper might be of interest to space syntax researchers
>>>> http://arxiv.org/ftp/arxiv/papers/0804/0804.1630.pdf
>>>> any comments are very welcome.
>>>>
>>>> Cheers.
>>>>
>>>> Bin
> -- 
> --------------------------------------------------------
> Bin Jiang
> Division of Geomatics, KTH Research School
> Department of Technology and Built Environment
> University of Gävle, SE-801 76 Gävle, Sweden
> Phone: +46-26-64 8901    Fax: +46-26-64 8828
> Email: [log in to unmask]  Web: http://fromto.hig.se/~bjg/
> --------------------------------------------------------
> European Associate Editor
> Computers, Environment and Urban Systems: An International Journal
>
> NordGISci: http://fromto.hig.se/~bjg/NordGISci/
> ICA Commission: http://fromto.hig.se/~bjg/ica/

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