models and methods for the optimal location of traffic sensors and vmss a. sforza

80
MODELS AND METHODS FOR THE OPTIMAL LOCATION OF TRAFFIC SENSORS AND VMSs A. Sforza DIS - Università di Napoli “Federico II “ Corso di Ottimizzazione su Rete A.A. 2010/11

Upload: paniz

Post on 18-Jan-2016

29 views

Category:

Documents


0 download

DESCRIPTION

MODELS AND METHODS FOR THE OPTIMAL LOCATION OF TRAFFIC SENSORS AND VMSs A. Sforza DIS - Università di Napoli “Federico II “ Corso di Ottimizzazione su Rete A.A. 2010/11. Outline of presentation. Context Flow intercepting facility location problems - PowerPoint PPT Presentation

TRANSCRIPT

Page 1: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

MODELS AND METHODS FOR THE OPTIMAL LOCATION OF

TRAFFIC SENSORS AND VMSs

A. SforzaDIS - Università di Napoli “Federico II “

Corso di Ottimizzazione su Rete

A.A. 2010/11

Page 2: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Outline of presentation

• Context– Flow intercepting facility location problems

• Applications in Traffic Management and Control

• Optimization models proposed in literature– Computational experience

– Proposals of new constraints

• A simple heuristic and some improving modifications

• Application to Traffic Network in Naples

Page 3: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Facility Location Problems

 

- Flow generating and/or attracting facilities

vertex – point – path

- Flow intercepting facilities

in vertices – on links

Page 4: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Flow generating and/or attracting facilitiesvertex location

Page 5: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Flow generating facilitiesService reaches the clients or vice-versa

Page 6: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Flow intercepting facilities

Page 7: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Flow intercepting facilities

Page 8: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Flow intercepting facilitiesO-D demand flows

Page 9: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Flow intercepting facilities in the vertices (two facilities)

Page 10: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Flow intercepting facilitieson the links (three facilities)

Page 11: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

The flow intercepting facility

location problem

is a problem of path covering

Page 12: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Applications in Traffic Management and Control

• Location of:

– Traffic counting sensors (for o-d matrix estimation)• To know a set of link flows or all the link flows

– Variable message systems• Fixed• Mobile

– Traffic checkpoints

Page 13: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Applications – Service Facilities A classification scheme

• Voluntary service facilities– Car service stations, automatic teller machine

• Unconscious service facilities– Traffic counting sensors

• Unvoluntary service facilities– Variable message signs

• Compulsory service facilities– Traffic check points– Inspection Stations

Page 14: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Traffic Management and Control Applications

Traffic counting sensors

No need of double counting

Variable message systems

There could be the need of

double (or more) intercepting

Page 15: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

m = 2 facilities

No double counting Double counting for path p2

p1 p2 p3 p1 p2 p3

Page 16: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Available information

- Information on path flows

- Information on link flows

- AssumptionThe flow pattern is not modified by facility location

This is surely true for traffic sensors

It could be not true for VMS

Page 17: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Information on path flows- Problem variablesInformation on path flows- Problem variables

  j N

yj =10

if there is a facility located at node jotherwise,

 

 

p P

xp=if at least one of the facilities is located on path potherwise,

10

G = (N, A)

N, set of vertices; A, set of links p path, P set of paths

Page 18: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

  

  

Max fp xp p P

n

s.t. yj = m j=1

yj xp pP j p

yj = 0, 1 xp = 0, 1

Model P1: Maximization of the intercepted flow with a fixed number of facilities

Page 19: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

  

  

n

Min yj

j=1

s.t. yj xp pP (1)jp

fp xp C*.

(2)

pP

yj = 0, 1 jN

xp= 0, 1 pP

Model P2: Minimization of the facility number

to intercept a fixed % of the total demand

Page 20: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Intercepting all the demanded flows

pP fpxp C*

If we want to intercept all the demanded flows

that is if C* = pP fp

pP fpxp pP fp xp = 1 pP

The second constraint disappearsThe first set of constraints becames

j p yj 1

Page 21: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

  

  

n

Min yj

j=1

s.t. yj 1 pP j p

yj = 0, 1 jN

Model P3: Minimization of the facility number to intercept the total demand

(i.e. to cover all the paths)

Page 22: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Model Output

Solving the model P1 produces the location of the m facilities giving the maximization of the intecepted flows, but it does not always give the exact values of the yp variables

Solving the model P2 produces the number and the location of the facilities needed to intercept a fixed percent of the total demand

and the list of the covered paths (i.e. exact values of yp variables)

Solving the model P3 produces the number and the location of the facilities needed to intercept the total demand (i.e. all the paths)

Page 23: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Location in vertices Location on links

Location in vertices is powerful for sensor location

to counting the flows of all the junction movement

It is possible from the technological viewpoint

using cameras and virtual sensors for each lane

and so for each movement in the junction.

Unfortunatly its result can be affected by errors,

sometimes relevant as we will see after.

For VMS location vertex location is not practicable,

because users have to be informed in the middle of the link

Page 24: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Transform a vertex model in a link modelthrough a dummy vertex

In any case a vertex model is much more manageable, because the number of variables is more tractable with respect to the number of variables of a link model.

Really it is possible to adopt a vertex model as a link model using a dummy vertex for each link

– For a single direction

– For both directions

Page 25: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Computational tests problem P1Nnodes_o/dpairs_pathsforodpairs_nodesforpaths

Network #nodes #plants Sol. value Gap% Time (secs)

N100_5_3_5 100 5 91 0.00 0.06

N200_10_3_10 200 10 183 0.00 0.05

N300_30_4_15 300 15 777 0.00 321.95

N500_50_5_20 500 25 1620 1.73 1h

N1000_100_5_25 1000 50 3020 5.40 1h

Page 26: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Computational tests problem P2 (60%)Nnodes_o/dpairs_pathsforodpairs_nodesforpaths

Network #nodes #plants Gap% Time (secs)

N100_5_3_5 100 2 0.00 0.02

N200_10_3_10 200 3 0.00 0.03

N300_30_4_15 300 7 0.00 0.78

N500_50_5_20 500 9 0.00 4.45

N1000_100_5_25 1000 16 0.00 593.22

Page 27: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Computational tests problem P3Nnodes_o/dpairs_pathsforodpairs_nodesforpaths

Network #nodes #plants Gap% Time (secs)

N100_5_3_5 100 3 0.00 0.02

N200_10_3_10 200 8 0.00 0.02

N300_30_4_15 300 17 0.00 134.56

N500_50_5_20 500 23 1.68 1h

N1000_100_5_25 1000 47 9.86 1h

Page 28: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Modification 1 of P2 model for traffic sensors location

The constraint (2) can be referred to a single o/d pair:

pPod fpxp C*

for each o/d pair of a given set of o/d pair

where Pod is the set of paths used to serve this o/d pair

Page 29: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Modification 2 of P2 model for traffic sensors and VMS location

To ensure that at least k paths of an od pair are intercepted the model can be integrated with the constraint:

pPod xp K

for each o/d pair of a given set of o/d pairwhere Pod is the set of paths used to serve this o/d pair

Page 30: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Modification 3 of P2 or P3 modelsfor VMS Location

To ensure that at least h plants intercept a path p

the model can be integrated with the constraint:

jp yj hfor each path p of a given set of relevant paths

Page 31: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Computational Times (sec)

Network: Modello P1 Modello P2(C) Modello P3

(C0) Number of nodes 60% 70% 80%

m t m t m t m t m t N100 5 0.23-1.92 3 1.70-0.81 4 2.59 (2) 5 2.43-3.63 8 0.89 N200 10 414.4-340.10 6 60.70-91.78 7 235.83-155.53 7-9 234.02-352.14 19 16.28 N300 8 20708.31 28 242.70 N500 38 1485.32 N700 49 2807.32

N1000 59 7916.89

Page 32: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

CT Modification 1 of P2 Model

Network: Modello P2(C,k) Number of nodes 60% 70% 80%

m t m t m t N100 7 4.62 7 5.57 7 12.02 N200 16 1226.90 16 1546.22 16 5519.96 N300 N500 N700

N1000

Page 33: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

CT Modification 2 of P2 Model

Network: Modello P2(C,P’) Number of nodes 60% 70% 80%

m t m t m t N100 18 329.51 18 312.38 * * N200

N300 N500 N700

N1000

Page 34: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Need of heuristic

For real networks with medium-large size

an heuristic approach seems unavoidable

Page 35: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

A small network

1

2

765

4 3

Path 1: 1- 2 - 5 Path 2: 1 - 2 – 4 Path 3: 1 – 3 – 4 Path 4: 1 – 3 – 7

Path 5: 2 - 5 Path 6: 2 – 4 - 6 Path 7: 3 – 4 - 6 Path 8: 3 – 7

Page 36: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

O/D paths

1

2

765

4 3

Path 1: 1- 2 – 5 (1) Path 2: 1 - 2 – 4 (2) Path 3: 1 – 3 – 4 (2) Path 4: 1 – 3 – 7(1)

Path 5: 2 – 5 (1) Path 6: 2 – 4 - 6 (1) Path 7: 3 – 4 – 6 (1) Path 8: 3 – 7 (1)

Page 37: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

A greedy heuristic[Berman et al. (1992), Yang and Zhou (1998)]

Coverage matrix B (path/link incidence matrix)

The rows correspond to the paths p p P

The columns correspond to the links a a A

Each element bpa = 1 if link a belongs to the path p= 0 otherwise

The coverage matrix can be obtainedwith an assignment model

Page 38: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

The coverage matrix B

Link

Path(flow) 1-2 1-3 2-4 3-4 2-5 4-6 3-7

p1(1) 1 0 0 0 1 0 0p2(2) 1 0 1 0 0 0 0p3(2) 0 1 0 1 0 0 0p4(1) 0 1 0 0 0 0 1p5(1) 0 0 0 0 1 0 0p6(1) 0 0 1 0 0 1 0p7(1) 0 0 0 1 0 1 0p8(1) 0 0 0 0 0 0 1

Page 39: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

A greedy heuristic[Berman et al. (1992), Yang and Zhou (1998)]

Scheme of the heuristicStep 0: set k=0. Let B(k) be the coverage matrix

Step 1: Compute fa(k)= f a

(k) , a A

Step 2: Find aj: fJ (k)= max a A{ fa

(k) } and locate a facility in link aj

(if more than one choose the link with lowest index,or better,

choose the link belonging to the greatest number of paths)

Step 3: Update the coverage matrix and generate B(k+1)

deleting the column corresponding to link aj

(bpj(k+1)=0 p P)

deleting the rows corresponding to the paths intercepted from a j)

(bpa(k+1)=0 a A, for each p such that bpj

(k)=1

Step 4: if bpa=0 p P, a A , then STOP.

otherwise, set k=k+1 and return to step 1

Page 40: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

First step of the heuristic

Link

Path(flow) 1-2 (3)

1-3 (3)

2-4 (3)

3-4 (3)

2-5 (2)

4-6 (2)

3-7 (2)

p1(1) 1 0 0 0 1 0 0p2(2) 1 0 1 0 0 0 0p3(2) 0 1 0 1 0 0 0p4(1) 0 1 0 0 0 0 1p5(1) 0 0 0 0 1 0 0p6(1) 0 0 1 0 0 1 0p7(1) 0 0 0 1 0 1 0p8(1) 0 0 0 0 0 0 1

Page 41: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Second step

Link

Path(flow) 1-2 (3)

1-3 (3)

2-4 (1)

3-4 (3)

2-5 (1)

4-6 (2)

3-7 (2)

p1(1) 1 0 0 0 1 0 0p2(2) 1 0 1 0 0 0 0p3(2) 0 1 0 1 0 0 0p4(1) 0 1 0 0 0 0 1p5(1) 0 0 0 0 1 0 0p6(1) 0 0 1 0 0 1 0p7(1) 0 0 0 1 0 1 0p8(1) 0 0 0 0 0 0 1

Page 42: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Third step

Link

Path(flow) 1-2 (3)

1-3 (3)

2-4 (1)

3-4 (1)

2-5 (1)

4-6 (2)

3-7 (1)

p1(1) 1 0 0 0 1 0 0p2(2) 1 0 1 0 0 0 0p3(2) 0 1 0 1 0 0 0p4(1) 0 1 0 0 0 0 1p5(1) 0 0 0 0 1 0 0p6(1) 0 0 1 0 0 1 0p7(1) 0 0 0 1 0 1 0p8(1) 0 0 0 0 0 0 1

Page 43: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Forth step

Link

Path(flow) 1-2 (3)

1-3 (3)

2-4 (0)

3-4 (0)

2-5 (1)

4-6 (2)

3-7 (1)

p1(1) 1 0 0 0 1 0 0p2(2) 1 0 1 0 0 0 0p3(2) 0 1 0 1 0 0 0p4(1) 0 1 0 0 0 0 1p5(1) 0 0 0 0 1 0 0p6(1) 0 0 1 0 0 1 0p7(1) 0 0 0 1 0 1 0p8(1) 0 0 0 0 0 0 1

Page 44: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Fifth and last step

Link

Path(flow) 1-2 (3)

1-3 (3)

2-4 (0)

3-4 (0)

2-5 (1)

4-6 (2)

3-7 (1)

p1(1) 1 0 0 0 1 0 0p2(2) 1 0 1 0 0 0 0p3(2) 0 1 0 1 0 0 0p4(1) 0 1 0 0 0 0 1p5(1) 0 0 0 0 1 0 0p6(1) 0 0 1 0 0 1 0p7(1) 0 0 0 1 0 1 0p8(1) 0 0 0 0 0 0 1

Page 45: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Comparison between heuristic and exact approach

This heuristic produces very fast solution,

but the result can be much far from the exact solution

Page 46: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Model P3 exact solution

4 facilities on links 2-4, 3-4, 2-5, 3-7

1

2

765

4 3

Path 1: 1- 2 – 5 (1) Path 2: 1 - 2 – 4 (2) Path 3: 1 – 3 – 4 (2) Path 4: 1 – 3 – 7(1)

Path 5: 2 – 5 (1) Path 6: 2 – 4 - 6 (1) Path 7: 3 – 4 – 6 (1) Path 8: 3 – 7 (1)

Page 47: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Greedy solution

5 facilities on links 1-2, 1-3, 2-5, 4-6, 3-7

1

2

765

4 3

Path 1: 1- 2 – 5 (1) Path 2: 1 - 2 – 4 (2) Path 3: 1 – 3 – 4 (2) Path 4: 1 – 3 – 7(1)

Path 5: 2 – 5 (1) Path 6: 2 – 4 - 6 (1) Path 7: 3 – 4 – 6 (1) Path 8: 3 – 7 (1)

Page 48: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

A simple improvement of the heuristic

The heuristic can be improved in the step 2

Step 2: Find aj: fJ (k)= max a A{ fa

(k) } and locate a facility in link a

(if more than one choose the link with lowest index)

Alternative

1. Choose the link belonging to the greatest number of paths

2. Modify the selection criterion of the links

Page 49: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

A simple network

3

2

41

5

10

O/D pair 1 – 9 2 – 9 2 – 10 3 – 10

Path 1: 1-4-7-9 Path 2: 2-5-7-9 Path 3: 2-5-8-10 Path 4: 3-6-8-10

6

7

8

9

Page 50: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Possible solution 1 (sub-optimal)

3

2

41

5

10

O/D pair 1 – 9 2 – 9 2 – 10 3 – 10

Path 1: 1-4-7-9 Path 2: 2-5-7-9 Path 3: 2-5-8-10 Path 4: 3-6-8-10

6

7

8

9

Page 51: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Possible solution 2 (optimal)

3

2

41

5

10

O/D pair 1 – 9 2 – 9 2 – 10 3 – 10

Path 1: 1-4-7-9 Path 2: 2-5-7-9 Path 3: 2-5-8-10 Path 4: 3-6-8-10

6

7

8

9

Page 52: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

The coverage matrix B

1-4

(1)

2-5

(2)

3-6

(1)

4-7

(1)

5-7

(1)

5-8

(1)

6-8

(1)

7-9

(2)

8-10

(2)

p1 1 1 1

p2 1 1 1

p3 1 1 1

p4 1 1

Page 53: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Step 1a

1-4

(1)

2-5

(2)

3-6

(1)

4-7

(1)

5-7

(1)

5-8

(1)

6-8

(1)

7-9

(2)

8-10

(2)

p1 1 1 1

p2 1 1 1

p3 1 1 1

p4 1 1

Page 54: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Step 1b

1-4

(1)

2-5

(2)

3-6

(1)

4-7

(1)

5-7

(1)

5-8

(1)

6-8

(1)

7-9

(2)

8-10

(2)

p1 1 1 1

p2 1 1 1

p3 1 1 1

p4 1 1 1

Page 55: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Step 1b

1-4

(1)

2-5

(2)

3-6

(1)

4-7

(1)

5-7

(1)

5-8

(1)

6-8

(1)

7-9

(2)

8-10

(2)

p1 1 1 1

p2 1 1 1

p3 1 1 1

p4 1 1 1

Page 56: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Step1c

1-4

(1)

2-5

(0)

3-6

(1)

4-7

(1)

5-7(0+1)

5-8(0+1)

6-8

(1)

7-9(1+1)

8-10(1+1)

p1 1 1 1

p2 1 1 1

p3 1 1 1

p4 1 1 1

Page 57: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Step 2a

1-4

(1)

2-5

(0)

3-6

(1)

4-7

(1)

5-7(0+1)

5-8(0+1)

6-8

(1)

7-9(1+1)

8-10(1+1)

p1 1 1 1

p2 1 1 1

p3 1 1 1

p4 1 1 1

Page 58: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Step 2b

1-4(0+1)

2-5

(0)

3-6

(1)

4-7

(1)

5-7 (0+1)

5-8(0+1)

6-8

(1)

7-9(1+1)

8-10(1+1)

p1 1 1 1

p2 1 1 1

p3 1 1 1

p4 1 1 1

Page 59: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Step 2b

1-4(0+1)

2-5

(0)

3-6

(1)

4-7

(1)

5-7 (0+1)

5-8(0+1)

6-8

(1)

7-9(1+1)

8-10(1+1)

p1 1 1 1

p2 1 1 1

p3 1 1 1

p4 1 1 1

Page 60: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Step 2c

1-4(0+1)

2-5

(0)

3-6

(1)

4-7

(1)

5-7 (0+1)

5-8(0+1)

6-8

(1)

7-9

(0)

8-10(1+1)

p1 1 1 1

p2 1 1 1

p3 1 1 1

p4 1 1 1

Page 61: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Step 3a

1-4(0+1)

2-5

(0)

3-6

(1)

4-7

(0+1)

5-7 (0+1)

5-8(0+1)

6-8

(1)

7-9

(0)

8-10(1+1)

p1 1 1 1

p2 1 1 1

p3 1 1 1

p4 1 1 1

Page 62: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Step 3b

1-4(0+1)

2-5

(0)

3-6

(1)

4-7

(0+1)

5-7 (0+1)

5-8(0+1)

6-8

(1)

7-9

(0)

8-10(1+1)

p1 1 1 1

p2 1 1 1

p3 1 1 1

p4 1 1 1

Page 63: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Step 3b

1-4(0+1)

2-5

(0)

3-6

(1)

4-7

(0+1)

5-7 (0+1)

5-8(0+1)

6-8

(1)

7-9

(0)

8-10(1+1)

p1 1 1 1

p2 1 1 1

p3 1 1 1

p4 1 1 1

Page 64: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Step 3c (all the flows are intercepted)

1-4(0+1)

2-5

(0)

3-6(0+1)

4-7

(0+1)

5-7 (0+1)

5-8(0+1)

6-8(0+1)

7-9

(0)

8-10

(0)

p1 1 1 1

p2 1 1 1

p3 1 1 1

p4 1 1 1

Page 65: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Check of the solution links

1-4(0+1)

2-5

(0)

3-6(0+1)

4-7

(0+1)

5-7 (0+1)

5-8(0+1)

6-8(0+1)

7-9

(0)

8-10

(0)

p1 1 1 1

p2 1 1 1

p3 1 1 1

p4 1 1 1

Page 66: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Final Solution

1-4(0+1)

2-5

(0)

3-6(0+1)

4-7

(0+1)

5-7 (0+1)

5-8(0+1)

6-8(0+1)

7-9

(0)

8-10

(0)

p1 1 1 1

p2 1 1 1

p3 1 1 1

p4 1 1 1

Page 67: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Revised greedy heuristic

Step 0: set k=0. Let B(k) be the coverage matrix

Step 1: For each link a A, compute [f1a(k), f2a

(k) ]

Where: f1a(k) is the flow to intercept

f2a(k) is the flow already intercepted

Step 2: Sort the links in decreasing lexicografic order with respect to the couple [f1a

(k), f2a(k) ] and locate a facility in the first link aj

Step 3: Update the coverage matrix and generate B(k+1)

- deleting the column corresponding to link aj

(bpj(k+1)=0 p P)

-deleting the rows corresponding to the paths intercepted with link aj

(bpa(k+1)=0 a A, for each p such that bpj

(k)=1)

Step 4: if bpa=0 p P, a A , then GoTo the Step 5. otherwise, set k=k+1 and return to Step 1

Step 5: Check the links inserted in the solution:If a link intercept flows intercepted from other links,remove it from the solution.

Page 68: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

A modification of the heuristic

The heuristic can be adapted

to the VMS location problem

when it is necessary

to intercept twice or more a specific path

Page 69: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

I step of the modified heuristic

Link

Path(flow) 1-2 (3)

1-3 (3)

2-4 (3)

3-4 (3)

2-5 (2)

4-6 (2)

3-7 (2)

p1(1) 1 0 0 0 1 0 0p2(2) 1 0 1 0 0 0 0p3(2) 0 1 0 1 0 0 0p4(1) 0 1 0 0 0 0 1p5(1) 0 0 0 0 1 0 0p6(1) 0 0 1 0 0 1 0p7(1) 0 0 0 1 0 1 0p8(1) 0 0 0 0 0 0 1

L

1 1

1 2

0 2

0 1

0 1

0 1

0 1

0 1

Page 70: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

II step of the modified heuristic

Link

Path(flow) 1-2 (0)

1-3 (3)

2-4 (3)

3-4 (3)

2-5 (1)

4-6 (2)

3-7 (2)

p1(1) 1 0 0 0 1 0 0p2(2) 1 0 1 0 0 0 0p3(2) 0 1 0 1 0 0 0p4(1) 0 1 0 0 0 0 1p5(1) 0 0 0 0 1 0 0p6(1) 0 0 1 0 0 1 0p7(1) 0 0 0 1 0 1 0p8(1) 0 0 0 0 0 0 1

L

1 1

1 2

1 2

1 1

0 1

0 1

0 1

0 1

Page 71: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

III step of the modified heuristic

Link

Path(flow) 1-2 (0)

1-3 (0)

2-4 (3)

3-4 (3)

2-5 (1)

4-6 (2)

3-7 (1)

p1(1) 1 0 0 0 1 0 0p2(2) 1 0 1 0 0 0 0p3(2) 0 1 0 1 0 0 0p4(1) 0 1 0 0 0 0 1p5(1) 0 0 0 0 1 0 0p6(1) 0 0 1 0 0 1 0p7(1) 0 0 0 1 0 1 0p8(1) 0 0 0 0 0 0 1

L

1 1

2 2

1 2

1 1

0 1

1 1

0 1

0 1

Page 72: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

IV step of the modified heuristic

Link

Path(flow) 1-2 (0)

1-3 (0)

2-4 (0)

3-4 (3)

2-5 (1)

4-6 (1)

3-7 (1)

p1(1) 1 0 0 0 1 0 0p2(2) 1 0 1 0 0 0 0p3(2) 0 1 0 1 0 0 0p4(1) 0 1 0 0 0 0 1p5(1) 0 0 0 0 1 0 0p6(1) 0 0 1 0 0 1 0p7(1) 0 0 0 1 0 1 0p8(1) 0 0 0 0 0 0 1

L

1 1

2 2

2 2

1 1

0 1

1 1

1 1

0 1

Page 73: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

V step of the modified heuristic

Link

Path(flow) 1-2 (0)

1-3 (0)

2-4 (0)

3-4 (0)

2-5 (1)

4-6 (0)

3-7 (1)

p1(1) 1 0 0 0 1 0 0p2(2) 1 0 1 0 0 0 0p3(2) 0 1 0 1 0 0 0p4(1) 0 1 0 0 0 0 1p5(1) 0 0 0 0 1 0 0p6(1) 0 0 1 0 0 1 0p7(1) 0 0 0 1 0 1 0p8(1) 0 0 0 0 0 0 1

L

1 1

2 2

2 2

1 1

1 1

1 1

1 1

0 1

Page 74: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

VI step of the modified heuristic

Link

Path(flow) 1-2 (0)

1-3 (0)

2-4 (0)

3-4 (0)

2-5 (0)

4-6 (0)

3-7 (1)

p1(1) 1 0 0 0 1 0 0p2(2) 1 0 1 0 0 0 0p3(2) 0 1 0 1 0 0 0p4(1) 0 1 0 0 0 0 1p5(1) 0 0 0 0 1 0 0p6(1) 0 0 1 0 0 1 0p7(1) 0 0 0 1 0 1 0p8(1) 0 0 0 0 0 0 1

L

1 1

2 2

2 2

1 1

1 1

1 1

1 1

1 1

Page 75: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

VII and last step of the modified heuristic

Link

Path(flow) 1-2 (0)

1-3 (0)

2-4 (0)

3-4 (0)

2-5 (0)

4-6 (0)

3-7 (0)

p1(1) 1 0 0 0 1 0 0p2(2) 1 0 1 0 0 0 0p3(2) 0 1 0 1 0 0 0p4(1) 0 1 0 0 0 0 1p5(1) 0 0 0 0 1 0 0p6(1) 0 0 1 0 0 1 0p7(1) 0 0 0 1 0 1 0p8(1) 0 0 0 0 0 0 1

L

1 1

2 2

2 2

1 1

1 1

1 1

1 1

1 1

Page 76: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Greedy solution

6 facilities on links 1-2, 1-3, 2-4, 3-4, 2-5, 3-7

1

2

765

4 3

Path 1: 1- 2 – 5 (1) Path 2: 1 - 2 – 4 (2) Path 3: 1 – 3 – 4 (2) Path 4: 1 – 3 – 7(1)

Path 5: 2 – 5 (1) Path 6: 2 – 4 - 6 (1) Path 7: 3 – 4 – 6 (1) Path 8: 3 – 7 (1)

Page 77: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Applications to TM in Naples

ATENA Project (1999-2002)(MURST, City of Naples, FIAT, University of Naples)

Low emission vehicle fleet experimentation

Telematic system for traffic management

Traffic monitoring and VMS

Traffic Supervisor

Page 78: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Work perspectives

Methodological schemeSensor location

UTM

VMS location

Process Scheme in ATIS scenario

Flow monitoring

Traffic Management

Message to the users

User behaviour and modification of the flow pattern

Return to Flow monitoring and Iterate

Page 79: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

Joint research perspectives

Proposal of research project (Prin 2003):

Infomobility and Transportation Network DesignRoma “La Sapienza” (coordination)

Camerino

Genova

Milano Politecnico

Napoli “Federico II”

Page 80: MODELS AND METHODS FOR THE OPTIMAL LOCATION OF  TRAFFIC SENSORS AND VMSs A. Sforza

References

• [1] Apollonio N., Caccetta L., Simeone B.. On complexity of path covering problems in graphs. AIRO Winter 2003 Conference.

• [2] Berman O., Hodgson M.J., Krass D.. Flow Interception Problem, in: Facility Location. A survey of application and methods. Ed. Drezner Z., Springler-Verlag. 389-426. (1995).

• [3] Berman O., Larson R.C., Fouska N.. Optimal Locating of Discretionary Facilities. Transportation Sciences. 26. 201-211. (1992).

• [4] Berman O., Krass D., Xu C.W.. Locating Discretionary Service Facilities Based on Probabilistic Customer Flows. Transportation Sciences. 29 (3). 276-290. (1995).

• [5] Berman O., Krass D., Xu C.W.. Locating Flow-InterceptingFacilities: New Approaches and Results. Annals of Operations Research. 60. 121-143. (1995).

• [6] Berman O., Krass D., Xu C.W.. A Generalized Discretionary Service Facility Location Models with Probabilistic Customer Flows. Stochastic Models. 13 (1). (1997).

• [7] Berman O., Krass D.. Flow intercepting spatial interaction model: a new approach to optimal location of competitive facilities. Location Science. 6. 41-65. (1998).

• [8] Bianco L., Confessore G., Reverberi P.. A network based model for traffic sensor location with implications on O/D matrix estimates. Transportation Sciences. 35 (1). 50-60. (2001).

• [9] Cascetta E., Nguyen S.. A unified framework for estimating or updating Origin/Destination trip matrices from traffic counts. Transportation Research B. 22. 437-455. (1988).

• [10] Confessore G., Dell’Olmo P., Gentili M.. An Approximation Algorithm for the Dominating by Path Problem. AIRO Winter 2003 Conference.

• [11] Hodgson M.J.. A Flow Capturing Location Allocation Model. Geographical Analysis. 22. 270-279. (1990).• [12] Lam W.H.K., Lo H.P.. Accuracy of O/D estimates from traffic counts. Traffic Engineering and Control. 31. 358-370.

(1990).• [13] Yang H., Zhou J.. Optimal Traffic Counting location for Origin-Destination matrix estimation. Transportation

Research. 32B (2). 109-126. (1998).