trans sys chap28

8/9/2019 Trans Sys Chap28

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Introduction to Transportation

Systems

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PART III:TRAVELER

TRANSPORTATION

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Chapter 28:Urban Public Transportation

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Urban Public Transportation Introduction

LOS Services History Costs Temporal Peaking and its Implications

Characteristics of the Industry A Model of Investment and Maintenance Service Design ITS Fares and Financial Viability Conclusion

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LOS Variables for Urban

TravelersLet us review our level-of-service variables

for travelers.)Travel time)Reliability)

Cost)Waiting time)Comfort)

Safety)Security

are all examples of level-of-service

variables that are relevant to any travelertransportation mode.5


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How Public Transportation

Measures Up Comfort in a crowded rush-hour subway

car is not high One has to wait for service depending on

the service frequency of the mode one is

considering Travel time may be greater or less than

that of an automobile, depending on the

circumstances How about self-image?

CLASS DISCUSSION6


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Some Other LOS VariablesSecurityAvailability of serviceSafetyAccessibility to service

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Types of Urban PublicTransportation Service

Conventional BusPara-TransitDemand-Responsive ServiceRail SystemsSubways

Commuter RailIntermodal Services

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Life-Cycle CostsCosts

M1

M3

M2 M4

CapitalCosts

0 1 2 3 4 time[M i is maintenance cost in year i]

9Figure 28.2


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DCF = Cc+ Mnn=1 (1 + i)nwhere Cc is the capital cost and iis an interest rate or discount rate

that reflects the time-value ofmoney as well as a risk factor.

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Maintenance Costs

= f( Quality of initial construction, current state ofinfrastructure, wear-and-tear caused by traffic)

Maintenance

InfrastructureWear-and-Tear

Maintenance

Figure 28.3

Wear-and-Tear

Quality ofInfrastructure

Time11


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Benefits of Maintenance as

a Function of InfrastructureQuality

Benefitof $1 ofMainte-nance

Quality ofInfrastructure

Poorly WellMaintained Maintained

12Figure 28.4


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The Impact of Delaying

Maintenance

Value ofInfrastructure

Benefit of

Benefit ofMaintenance of $M

Wear-and-Tear

Maintenance of $M

Time

Figure 28.5 13


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Wear-and-Tear as a Function

of Infrastructure Quality

Wear-

and-TearCausedby Unit ofTraffic

InfrastructurePoorlyMaintained

WellMaintained Quality

Infrastructure Infrastructure

14Figure 28.6


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LOS as a Function of Quality

of Infrastructure

LOS

Quality of

Infrastructure15

Figure 28.7


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The Vicious Cycle

The quality of our infrastructuredeteriorates, level-of-servicedeteriorates, and considering theequilibrium framework, traffic

volumes will deteriorate.So revenue goes down and there

are even fewer dollars to spend to

improve our infrastructure bycounterbalancing the effects ofwear-and-tear throughmaintenance.

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The Vehicle CycleThe basic equation for sizing a fleet is as follows:

NVEH = VC

HEADWAY

where NVEH is number of vehicles in the fleet;VC is the vehicle cycle on this route -- the time ittakes the vehicle to traverse the entire route; and

HEADWAY is the scheduled time betweenconsecutive vehicles.

Alternatively,

NVEH = FREQUENCY VC

where FREQUENCYis the number of vehicles

per unit of time passing a point on the route.17


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Vehicle Cycle1 hour

1 hourSuppose we want a service frequency of four

vehicles per hour.

How many vehicles do we need? How would you reduce the number ofvehicles needed?

CLASS DISCUSSIONFigure 28.8 18


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Control Strategies for Rail

SystemHolding TrainsStation-Skipping

Short-TurningA A A

1 2

A A AFigures 28.10, 28.11 19


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ITS -- Public Transportation

Applications The ITS concept, described in Chapter

24, can be applied to publictransportation. These applications,known collectively as Advanced Public

Transportation Systems (APTS), includesuch technologies as automatic vehiclelocation and automatic passengercounters, which can provide the basis formore efficient fleet managementsystems, both in fixed rail and bussystems.

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Traveler Information through

ITSIntermodal Transfers

There are operating strategies that wouldallow transit systems to operate moreeffectively. These strategies areinformation-driven and ITS technologiescan be a boon to the transit industry both inimproving operations and service and in

providing timely information to travelers.The latter in and of itself could be animportant market initiative for the public

transportation industry.21


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Fares, Ridership and

FinanceFares

ServicesOffered (Ridership)Volume

FinancialSituation

Subsidy

RevenuesCosts

22Figure 28.12


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Linear Demand FunctionV [Volume]

V0

FMAX F [Fare]

(Fopt = Fmax/2)

Figure 28.13 23


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Parabolic Demand FunctionV [Volume]

V0

parabola

FMAX F [Fare]

(Fopt = Fmax/3)

Figure 28.14 24


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Inelastic Demand FunctionV [Volume]

V0

F [Fare]

The horizontal line would reflect little or no changein demand (inelastic demand) as a function of farefor some range of fares. So why not simply raise fares and hence revenue? Equity Air Quality Congestion on highways

Figure 28.15 25

trans sys chap28

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