A Novel Accessibility (Serviceability) Measure using Travel Time and Space Syntax Indices

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A Novel Accessibility (Serviceability) Measure using Travel Time and Space Syntax Indices Lee, Seungjae

Lee , Byoungwook

University Of Seoul

Contents

Introduction1

Definition of Serviceability2

Measuring Serviceability with Space Syntax and Travel Time4

Applying to Kangnam area4

Conclusion

5

Basic Concept3

6

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Environment-friendly Operation & Mgmt. of

transport facility-centric

Public transport-

centric

Car-oriented

Private car-centric

Construction of transport facility -

centric

Development-oriented

People-oriented

Paradigm Shift on Transport Policy

Seoul PublicTransport Reform

Seoul Public Transport Reform Begins from July, 2004

Introduction

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Introduction

Exclusive Median Arterial Bus Lane

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Introduction

Bus speedincrease

Bus speedincrease

Securing punctualitySecuring

punctualityConvenienceimprovement

Convenienceimprovement

Lack of dwelling area due to street facilities

Interruption / outer lane stop

Exclusive lane for bus

Separated dwelling area for bus passengers

Exclusive Median Arterial Bus Lane

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MEDIAN ARTERIAL BUS LANE IN SEOUL

Introduction

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Introduction MEDIAN ARTERIAL BUS LANE IN SEOUL

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Introduction

Accessibility (Serviceability) is being focused more attention by planners recently

Seoul City has redesigned the Bus Network systems to Hierarchical (corridor and feeder) systems

Also implemented the bus network system with “Median bus lane” for improving the bus speed and access

Need to measure the serviceability for evaluating how much the serviceability is improved

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Definition of Serviceability

General meaning of Accessibility Ability to obtain goods, services and activities How fast CBD or Critical Area is approached

Serviceability in this study Ability to approach to bus stops Can represent as a meaning of “Serviceability” General meaning of Serviceability is

“the quality of being able to provide good service by public transport”

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Basic Concept

Previous bus line

Hierarchical line

Feeder Corridor

Travel time

DistanceOrigin

Destination

Transfer

Transfer

Critical Point

Travel time of Feeder line

Travel time of Corridor line

In-vehicle time of Previous line with feeder

In-vehicle time of Hierarchical line with corridor Waiting and transfer time

Feeder

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Measuring Serviceability with Space Syntax and Travel Time

What is Space Syntax?What is Space Syntax?What is Space Syntax?What is Space Syntax?

Space syntax is the technique to analyze the connectivity of urban or architectural spaces.

Has been applied to analyzing movement in indoor spaces or pedestrian paths (not in transport network).

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Space Syntax Representation

The difference of axial lines and transportation networks

A

B

C

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Space syntax Analysis

Seoul network

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• Movement can be described in an abstracted form using its topology.

• Topological description helps focus on the structural relationship among units.– For example, pedestrian movement can be

described using network of simple lines without considering the details such as sizes of forms, number of people and speed of movement.

Hierarchical Network Configuration

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• Topological description of streets network

1

2

3

6

4

5

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• Hierarchical structure of a street– Representing each component with a node

and a turn with a link connecting their respective nodes

1

2 3

4 5

6

step 1

step 2

step 3


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• This relationship is described as a variable called depth.– Depth of one node from another can be

directly measured by counting the number of steps (or turns) between two nodes.


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• Total Depth(TD)

– TD1 = 1 x 2 + 2 x 2 + 3 x 1 = 9

m

ssi NsTD

1

TDi : the total depth of node is : the step from node im : the maximum number of steps extended from node iNs : the number of nodes at step s


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• Mean Depth(MD) = TD / (k-1)

• Normalized Depth(ND)

12

3

4

1

2

3

4

step k -1

1

2 3 4

432

1

step 1

b. completely asymmetrical network

a. completely symmetrical network

※ k : the total number of nodes

21

2/)1(

1

)1(...21 k

k

kk

k

kMD

11

1

k

kMD

21

kMD 1

2

)1(20

k

MD


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Calculation of Space Syntax Integration Value

Representation of axial lines

E

S

3

1

2

4

5

6

79

3

8

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1 9

2 4 5

1 7 9

2 5 6

7 8 9

step 1

step 2

step 3

2

5

4

73 8 9

1

step 1

step 2

step 3

1 7

4

9

step 1

step 2

step 3

8

5

6

6

1

2

5 6

3

7 8 9

4

2 5

3

4 6

1

3 8 3

4 2

8

6

7

3

9

7

1 8

4

2 5 6

3 1 3 9

4 5

8

6 7

2

7

9

1

4

2 5 6

38

Mapping schematic route connectivity onto a graph

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Stop No. TD MD ND ND-1

1 16 2 0.333 3.000

2 17 2.125 0.375 2.667

3 12 1.5 0.167 6.000

4 11 1.375 0.125 8.000

5 17 2 0.375 2.667

6 16 2.125 0.333 3.000

7 17 2 0.375 2.667

8 13 1.625 0.208 4.800

9 17 2.125 0.375 2.667

Computing depth from each road

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Measuring Serviceability with Space Syntax

Computing “Inner Product”Computing “Inner Product”Computing “Inner Product”Computing “Inner Product”

We use the Bus stop as a base. But Base Unit of Space Syntax is “Axial line”

There are some problems to change the results according to the location of turns.

So we use “Inner Product” based “Link”

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Assuming Space Syntax’s axial line is affected by the adjacent lines. (right and left lines crossing Space Syntax Axial.)

We can compute below Point to Point Point to all

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Assuming this network

Each actual line has each Space Syntax value “a0, a1, a2, , a‥‥ k-1, ak”

a0

‥‥‥‥

‥‥‥‥

a1 a2 ak-1 aka3

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Computing as below



0

f

n

1k

2

21

2

1),(

W

IP a

a

aaaa

k

kkkk

)1(1

2

1

1

21

2

na

aa

Wn

k

k

n

k

kk

f

1

1

1

)1,(

0

n

aaIPa

n

k

kkWhere,

1i,IP iaa

fW

n

ia

: Inner product between i & i+1

: Value of axial line i

: weighting factor

: Number of total crossing line

,

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Assuming simple network


7299.0381175

811117752222

222222

Wf

59.697299.081175

752222

22

75

IP

Example of Computing “Inner Product”Example of Computing “Inner Product”Example of Computing “Inner Product”Example of Computing “Inner Product”

9

5 7 11 8Value of space syntax

IP5-7

99.997299.081175

1172222

22

117

IP

42.1097299.081175

8112222

22

811

IP

IP7-11 IP11-8

93

42.1099.959.6

1

1

1

)1,(

0

n

aaIPa

n

k

kk

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Computing as below

Where,

Sbi,j = serviceability from i to j

IPi,j = Space Syntax value using Inner Product from i to j

TTi,j = Travel Time from i to j

α and β can be estimated for weighting the Sb function or a bi-criteria method can be used to calculate the Sb function in a general purpose


Computing serviceabilityComputing serviceabilityComputing serviceabilityComputing serviceability

)()( ,,, jijiji TTIPSb

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Judgment of Serviceability

Travel time with Transfer

Computing Inner Product

Bus Line’s Space Syntax

Measuring Order Measuring Order Measuring Order Measuring Order

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1

6

7

9

8

5

4324KM 6KM 4KM 5KM 3KM

2KM

5KM

4KM

5KM

Example of Proto-type NetworksExample of Proto-type NetworksExample of Proto-type NetworksExample of Proto-type Networks

Speed : 20km/h

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Measuring Serviceability with Space Syntax and Travel TimeResults of Proto-type NetworksResults of Proto-type NetworksResults of Proto-type NetworksResults of Proto-type Networks

9

9

9

11

8 8 8

9 9

9 9

9 9

11

8.66

8.66

8.66 8.66

8.668.66

9.679.67

1

6

7

9

8

5

432

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Results with Travel Time of Proto-type NetworksResults with Travel Time of Proto-type NetworksResults with Travel Time of Proto-type NetworksResults with Travel Time of Proto-type Networks

Point to others Inner Product Travel time

Stop.1 22.23 46.16

Stop.2 15.23 33.50

Stop.3 14.23 37.72

Stop.4 17.23 37.94

Stop.5 18.01 43.50

Stop.6 20.88 52.66

Stop.7 20.04 41.83

Stop.8 21.99 49.94

Stop.9 26.34 61.83

* *

* Average value

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0

10

20

30

40

50

60

70

0 5 10 15 20 25 30Inner Product

Travel Time

Stop.2Stop.3Stop.4Stop.5Stop.6Stop.7Stop.8Stop.9Stop.1

Results with Travel Time of Proto-Type NetworksResults with Travel Time of Proto-Type NetworksResults with Travel Time of Proto-Type NetworksResults with Travel Time of Proto-Type Networks

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Applying to Seoul

Comparing Bus line accessibility between before and afterComparing Bus line accessibility between before and afterComparing Bus line accessibility between before and afterComparing Bus line accessibility between before and after

Comparing between before and after

Using Seoul city’s speed date and real distance from a bus stop to a bus stop*

20km/h with Median bus lane, others 15km/h which are the mean speeds of Seoul’s networks

Measuring how the Serviceability is improved

* www.bus.go.kr

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Applying to Seoul(Kangnam)

Before

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After

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Jamsil

N a m b u Bus TerminalKangnam St.

Apgujeong

National Univ. of Education

15.7435.71 16.9337.48

Travel TimeInner Product

26.9796.78 24.6588.97

TravelTimeInner Product

100.87 25.2226.5110.12

TravelTimeInner Product23.4277.22 29.43117.81

Travel TimeInner Product

AfterAfter BeforeBefore

Travel Time(min)Inner Product

index

Express Bus Terminal

22.7176.98 30.8392.35

TravelTimeInner Product

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Conclusion

Developed the methodology of measuring serviceability using Space Syntax and travel time measures

We compared with Before and After bus network system to use some of selected bus lines in Kangnam area

This method has a limitation due to its complexity If IP(Inner product) and Travel Time are small, that it

means serviceability is good.Hierarchical bus network system is more accessible

than the previous bus network system

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Documents

A Novel Accessibility (Serviceability) Measure using Travel Time and Space Syntax Indices