Public Transport Network Design and Appraisal

- a case study of Porto

Álvaro Costa, Pedro Abrantes, Oana Grozavu and Sílvia MagalhãesCITTA – Centro de Investigação do Território, Transportes e Ambiente

10th EWGT Meeting, Poznan, 13-16th September 2005

Contents1. Introduction2. Re-designing Porto bus system3. Network Appraisal Methodology4. Impact of LRT Network5. Impact of Strategic Bus Network6. Local vs Global Accessibility7. Global Efficiency Indicators8. Conclusions9. Further Research

1.1. Introduction• Porto Metropolitan Area pop.: 1.2 mi

• New light rail system (Metro do Porto)

• New integrated ticketing system (Andante)

• Need to restructure bus network for greater integration and efficiency

• New network design based on “professional judgement” (heuristic method?)

• CITTA commissioned to:• evaluate its public acceptability and

efficiency• suggest improvements where

necessary

1.2. Introduction - OR analogy• Starting point: existing STCP bus

network (red) + metro (blue)

• 81 bus lines (to be cut down to 50)

• Problem: Guaranteeing public acceptability and increased efficiency while minimizing change

• I.e., heavily constrained problem, but poorly defined constraints

• Solution: Iterative, piece meal, client-driven approach (“trial & error”) to ensure feasibility of solution = optimization in the real world

• Strong emphasis on GIS analysis of results.

Change in bus service frequency (bue = increase)

2. Re-designing Porto bus system

• Design criteria:– Shorten lines– Modal integration– Homogeneous

frequencies– 80 50 lines

• Result:– 17% veh-km reduction– Decrease in radial

services– Increase in orbital

services

3.1. Network Appraisal Methology

• Public Transport Assignment Model (EMME/2)

• Fixed demand from 2001 household travel survey

• Network Scenarios:– 10: Bus0– 20: Bus0 + Metro– 30: Bus1 + Metro– 3x: Busx + Metro

• Accessibility analysis• Efficiency analysis

3.2. Network Appraisal Methology

• Accessibility indicator (GIS plots) : Average generalized travel time by destination zone

• Efficiency indicators:Fleet size, Veh-kms, Total trips (operator)Pax-kms, travel time, walk time, number of interchanges (users)

iiD

iiDiD

DT

TGTTGTT

)(

ijijijijij InVehTTransferTWaitTWalkTGTT

4.1. Analysis of Results - Impact of the LRT Network

Change in accessibility between scenarios 10 and 20

• As expected, LRT brings about significant travel time reductions (up to 12 min)

• Greatest benefits along LRT

• Large gains up to a significant distance from LRT, because of bus-LRT difference in speed(25km/h vs 13km/h)

dTT20-10-30 - -16-16 - -8-8 - -4-4 - -2-2 - -1-1 - -0.5-0.5 - 0.5-0.5 - 11 - 22 - 44 - 88 - 1616 - 30

Linhas metro_a.shpAmp_conc.shp

dTT média global - cenário 20 vs cenário 10

Mapa nº 3

4.2. Analysis of Results – Impact of the LRT Network

Change in bus passenger flows between scenarios 10 and 20

• General reduction in bus pax flows

• Small increases in certain suburban/orbital routes

• Potential complementary role of bus in new network

5.1. Analysis of Results - Impact of the Strategic Bus Network

Change in accessibility between scenarios 20 and 30

• Significant travel time increases (≤ 8 min): poorer coverage or service transfer to private sector

• Significant gains in some suburban zones (≤ 10 min): improved LRT access, successful integration ☺

• Gains from metro outweigh losses from new bus network in nearly all zones (special zones treated later)

• Policy implication Metro + Bus1 must be introduced at same time

dTT média global - cenário 30 vs cenário 20

dTT30-20-30 - -16-16 - -8-8 - -4-4 - -2-2 - -1-1 - -0.5-0.5 - 0.5-0.5 - 11 - 22 - 44 - 88 - 1616 - 30

Linhas metro_a.shpAmp_conc.shp

Mapa nº 4

5.2. Analysis of Results - Impact of the Strategic Bus Network

Change in bus passenger flows between scenarios 20 and 30

• Reduction in radial flows, esp. around city centre, due to reduced frequency

• Significant increases in orbital flows, esp. towards main metro interfaces

• Explains gains away from LRT route bus services play an important role as feeders to LRT

5.3.Analysis of Results – Impact on the pattern of trip interchanges

Change in transfer boardings between scenarios 10 and 30 (red=increase)

• Concentration of intechanges around key metro stations

• Bus increasingly becomes a feeder mode to LRT. Bus-bus transfers decrease significantly

• Policy implications:– Improve interchange facilities to

take full advantage of new mode– Minimize distance between bus

and metro stops

6.1. Local vs Global Accessibility

• Problem: Some zones lose accessibility from sce. 10 to 30

• Further investigation showed inconsistencies in network design:– Zones furthest away from

metro miss out the most with the new bus network

– Those zones also happen to be important centres for surrounding n’hoods

Delta_TT_5-3.shp-24 - -12-12 - -6-6 - -3-3 - -1-1 - 11 - 33 - 66 - 1212 - 24

Linhas metro

TT 5 - 3

Change in accessibility scenarios 1 to 3

Tempo total 5-6.shp-24 - -12-12 - -6-6 - -3-3 - -1-1 - 11 - 33 - 66 - 1212 - 24

Linhas metro

TT 5 - 6

Change in accessibility scenarios 2 to 3

Diagrams attempt to illustrate the problem

• The new bus network improves access to metro stations, which in turn greatly improve access to distant parts of the city

• Yet, reduced network coverage decreases local accessibility

• As we started by looking at the whole metropolitan area, this problem went nearly unnoticed

• Policy outcome: strengthen local bus services

6.2. Local vs Global Accessibility

7.1. Global efficiency indicators – User perspective

• 3% mean travel time decrease from sc. 10 to 20

• Constant travel time from 20 to 30

• 1.5% mean travel distance decrease from sc. 10 to 20

• 1.5% mean travel distance decrease from sc. 20 to 30

• Notice significant pax-kms transfer to metro due to new bus network (+10%)

36.16

34.98

34.95

34 34.5 35 35.5 36 36.5

10

20

30

Scen

ario

Average generalized travel time (min)

198,951

162,949

154,650

33,347

36,352

0 50,000 100,000 150,000 200,000 250,000

10

20

30Sc

enar

ios

Pax-kms

bus

metro

7.1. Global efficiency indicators – User perspective

• Metro does not produce an increase in av. interchanges

• New bus network actually reduces interchanges

• But at the cost of greater walk access time

• Still, no increase in travel time

1.45

1.44

1.41

1.39 1.4 1.41 1.42 1.43 1.44 1.45 1.46

10

20

30

Scen

ario

Average number of boardings per trip

7.45

7.17

7.91

6.60 6.80 7.00 7.20 7.40 7.60 7.80 8.00

10

20

30Sc

enar

io

walk time (min)

7.2. Global efficiency indicators – Operator perspective

• 14% decrease in fleet size requirements

• 4.2% decrease in morning peak hour veh-kms travelled

• Conclusion: Significant savings achieved, while maintaining or improving accessiblity by applying simple network design rules

• “Operator happy, passengers happy”

  Fleet size Veh-kms

    (AM peak hr)

Bus_0 389 7676

Bus_1 333 7350

delta -14.4% -4.2%

8. Conclusions

• Useful methodology, popular with decision makers and public

• Benefits from LRT line are significant, and spread beyond the route

• Scale of benefits depends on bus service design bus plays an important feeder role in the LRT network

• It is possible to achieve significant gains in accessibility by re-designing the bus system for better integration with LRT network

• Furthermore,it is possible to do this while improving efficiency (inc. fewer resources)

• Nevertheless there is a trade-off between local and global accessibility in some areas, which is not visible when analysing accessibility across whole area

9. Future research• Incorporate elastic demand model

• Introduce outstanding operators and differentiated fare system

• Develop optimization algorithms to find the “optimum network”

• Test the impact of other policy measures, eg bus priority

Questions & comments

Pedro AbrantesCITTAFaculdade de Engenharia da Universidade do Portopala@fe.up.pt

See presentation on www.fe.up.pt/~pala from 20th Sept