Dear Chengke,
To add to Alan comments:
a/ What kind of road counts do you use? Are they mainly expressways, trunks road, main roads? If so try global measure. Traffic flow level is also dependant on capacity (useable width or lane number) so this may impact on your analysis.
b/ if there are global movement roads it might be that your model coverage is too small. Large scale movement require a regional model size.
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Alain Chiaradia
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-----Original Message-----
From: Chengke LIU
Sent: 21 January 2007 10:18
To:
Subject: Poor correlation between local integration and traffic flow in Kowloon, Hong Kong
Deal all,
I have finished drawing axial lines of one district of Hong Kong - Kowloon,
totally 3004 axial lines. Also I pin-pointed all the counting stations on
those axial lines. I calculated local integration of axial lines and
compared it with the natural logarithm of the average traffic flow of that
corresponding axial line. To my disappointment, the correlation is quite
poor, r square value is only 0.10. I am not sure why the correlation is so
poor, the possible reasons are listed as follows:
1.The street network in Hong Kong is very complex, I digitized some road
lines with only one axial lines, since they represents different lanes for
different traffic direction. And even, somewhere a cluster of roads are
represented for only one axial line for simplification.
2.Due to lacking of time and manpower, I did not take those overpass and
underpass roads into consideration when I calculated the connectivity value
of axial lines. When I digitized the axial map, I only referred to the
digital street and building maps of Hong Kong at hand. Some lines are
apparently intersected on digital map, but actually they are not, since one
of them is overpass or underpass road.
3.When I assigned the traffic flow the axial lines, I first pin-pointed
counting stations on roads to corresponding axial line, and then averaged
the traffic flow.
4.The spatial configuration (space syntax) is not suitable in Hong Kong to
predict traffic flow.
The above factors are responsible for the poor correlation from my point of
view. What do you think about this problem? Since Kowloon is only one
district of Hong Kong, I need to continue with the whole Hong Kong
territory. If something wrong in above 4 factors, please point it out, so I
can correct it early. Your comments are highly appreciated!
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