1 tradable travel credit schemes for network mobility management...

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Tradable Travel Credit Schemes for Network

Mobility Management

基于可交易电子路票的网络交通流控制与管理

Hai Yang

Chair Professor

Department of Civil and Environmental Engineering,

The Hong Kong University of Science and Technology

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Outline

Introduction to tradable travel credit schemes

Model formulation and properties of the tradable

credit schemes

Trial-and-error implementation of congestion

pricing / tradable credit schemes with unknown

demand function

Ongoing researches

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Pricing and Quantity Instruments for Network Mobility Management

（交通网络流控制的价格和数量调控手段） Pricing Instrument ( 价格调控 )

Efficient utilization of limited network resources 有效地利用有限的网络资源

Inequality problem etc. public opposition 有失公平大众反对

Quantity Instrument ( 数量调控 )Road space rationing

如：单双号限行

Tradable travel credit scheme 可交易的电子路票

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Road Space Rationing (e.g., Beijing and Guangzhou)

Restrict private cars’ access to roads on a uniform fraction of days.

Effective (short-term).

More equitable (?)

Low efficiency (spatially and temporally).

Long-run policy may lead to a sharp increase of old, cheap and high-polluting second-car consumption (negative impact to the environment).

Wang X.L. and Yang H. 2010. Traffic rationing and short-term and long-term equilibrium. Transportation Research Record.

Han, D., Yang, H., Wang X.L., 2010. Efficiency of the plate-number-based traffic rationing in general networks. Transportation Research Part E.

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Introduction to Tradable Travel Credit Schemes（可交易电子路票概念简介）

Each participating agent receives a proportion of credits (on a periodic basis such a month or a quarter)

在每阶段初（如每个月初）每位出行者会得到一定数量的电子路票 Equity ( 公平 )

Initial distribution for free ( 最初发放的电子路票是免费的 )

Revenue neutral incentives for mobility and environmental quality

政府财政收入为零 ( 不收取或支付任何费用 ) ，有助于明确其缓解拥堵和减少污染的决心，减少公众对该项措施的质疑

Credit charging scheme （电子路票收取方案） Link-specific or cordon-based; distance or time-based; time-invariant or time-

varying

电子路票收取可基于路段或境界线；基于路程或时间；不随时间变化或随时间变化的

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A policy target in terms of fix-quantity travel credits can be easily achieved

可通过最初电子路票的总发放数量来确定并达成政策目标

Example: Distance-based credit charge for achieving control of total veh-km traveled on the network

如：在基于路程的电子路票收取方案下，总的车辆行使路程被总的电子行驶券发放数量控制

Introduction to Tradable Travel Credit Schemes （可交易电子电子路票概念简介）

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The equilibrium price of credits is determined by the market through free trading.

电子路票可在市场上自由交易

Market driven

价格由市场决定

Enhance income distribution or financial transfer confined only to within the predefined group of travelers (credit flow from the higher income groups to the lower; the flow of money from the wealthy to the less)

有助于收入再分配，优化资源配置 ( 电子路票从低收入人群流向高收入人群的同时，货币反向从高收入人群流入低收入人群 )

Introduction to Tradable Travel Credit Schemes （可交易电子路票概念简介）

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Recent Study:Yang, H. and Wang, X.L. (2011) Managing network mobility with

tradable credits. Transportation Research 45B (3) 580-594.

Equivalent Optimization Problem

First-Order Optimality Conditions:

subject to

, , , w

a r w a rw W r R

v f a A

0,

min dav

av fa

t

, , w

r w wr R

f d w W

a aa A

v K

* *, , 0, ,a a a a r w r w w

a A

t v p f r R w W

*, 0, ,a a a a r w w

a A

t v p r R w W

, 0, ,r w wf r R w W

* 0a aa

v K p

*a a

a

v K

*, 0, ,r w wf r R w W

0p

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For a given credit scheme, a unique equilibrium flow pattern exists; the equilibrium credit price is unique subject only to very mild assumptions.

Proposition 1. Given a tradable credit scheme ,K , the credit

price *p at equilibrium is unique if there exists at least one O-D pair

whose equilibrium path set always contains the same two (or more) paths

with different credit charges.

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A properly designed tradable credit scheme (total amount of credits issued and individual link credit charges) can emulate a congestion pricing system and support various desirable traffic flow optima:

Social optimum

Capacity constrained traffic flow pattern

Pareto-improving and revenue-neutral

Proposition 3. Given an SO credit charging scheme, so , and a total amount

of credits issued, so so soa aa A

K v

, if the credit price *p at market

equilibrium is unique and the total system travel time at SO is strictly less than

that at UE without any policy intervention, then there exists an O-D based

credit-distribution scheme that can make every traveler strictly better off.

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Link travel time: 1 1 18 2t v v , 2 2 216t v v

O-D demand: 1 2 10d ,

Initial credit allocation: 30K , 1 2 3k

Link credit charge: 1 4 , 2 2 .

2

1

1Link 1; 4

Traffic Equilibrium and Market Equilibrium with Tradable Credits: An Example

2Link 2; 2

User equilibrium and credit market equilibrium conditions:

1 2

1 2

1 2

8 2 4 16 2

10

4 2 30

v p v p

v v

v v

A unique equilibrium solution:

Link flow: * *1 2 5v v

Link travel time: *1 18t , *

2 21t

Unit credit price; * 1.5p

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Analytical demand functions tailored for traffic demand control are difficult to establish in practice even with advanced transport modeling techniques.

- Individual users’ valuation of trip-making (hiddeninformation)

- Anonymous individual users’ behavior (hidden action)

A fundamental question: how to design the optimal credit scheme (credit allocation and charge) in a simple yet practical manner ?

Implementation Issue under Limited Information(for both pricing and tradable credit schemes)

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Bisection Method for Trial-and-Error Implementation of Marginal Cost Pricing on a Single Road

0d0d 1d

0

01

1

1d

n n nd t d

B d

AC d

MC d

demand d

nd

1

1

2n n nd d d

0n nd d

SO

0d

Gen

eral

ized

co

st

d*

1n

n

SO

Li, M. Z. F., 2002. The role of speed-flow relationship in congestion pricing implementation with an application to Singapore. Transportation Research 36B (8), 731-754.Yang, H., Meng, Q., Lee, D.H., 2004. Trial-and-error implementation of marginal-cost pricing on networks in the absence of demand functions. Transportation Research Part B 38 (6), 477-493.

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Trial-and-error Implementation with Unknown Demand Function: Similarity and Difference between

Tradable Credit and Congestion Pricing Schemes

Congestion pricing: Tradable credit scheme

Equilibrium Traffic equilibrium Traffic equilibriumCredit market equilibrium

Decision variable

Link toll charge Link credit charge Total amount of credits issued

Available Information

Observed link flow Observed link flow Revealed unit credit price

The revealed credit price becomes available, signalizing the necessity for an upward or downward adjustment of the total amount of credits to be issued in a subsequent implementation period.

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Trial-and-error Procedure for Tradable Credit Schemes

0d0 0p d 1d 1 1p d

0ad 0

bd1ad 1

bd

1

1

1 11

max ,min ,

min ,max ,

2

n n n n na a

n n n n nb b

n nn a b

d d d p d

d d d p d

d dd

SO

otherwise

1n n

B d

MC d

AC d

demand d

,

n n n n n nd t d K d

observe

np

0n

0 0 00, ,nuea bd d d d

nued

1

2

1 orn

n na b

p

d d

Gen

eral

ized

co

st

SO

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Numerical Example

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* 1.0p p * 22.6d d

Optimal solution is found after 6 trials

* 22.6d

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Trial-and-error Implementation of Congestion Pricing / Tradable Credit Schemes on Networks with Unknown Demand Function

no

SO

yes

Try the pricing scheme n

0?n nv v

1n n

Observe a flow pattern nv

Set 0n . Choose an initial trial flow 0v , and set a trial pricing scheme 0 based on 0v .

Update the trial flow 1nv based on nv and nv . Set a new pricing scheme 1n based on 1nv .

Yang, H., Meng, Q., Lee, D.H., 2004. Trial-and-error implementation of marginal-cost pricing on networks in the absence of demand functions. Transportation Research Part B 38 (6), 477-493.

Yang, H., Xu, W., He, B.S. and Meng, Q., 2010. Road pricing for congestion control with unknown demand and cost functions. Transportation Research Part C 18 (2), 157-175.

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Following Research:

Tradable credit scheme with heterogeneous travelers (discrete set of VOT or continuously distributed VOT) (Wang et al., 2011; Zhu et al.. 2011)

Tradable credit scheme with transaction costs (Nie, 2011)

Tradable credit scheme with income effects (Yin et al., 2011)

Managing bottleneck congestion with tradable credits (Xiao and Zhang, 2011)

Tradable credit schemes for managing bottleneck congestion and modal split with heterogeneous users (Tian, Yang and Huang, 2011)

Tradable credit schemes for multi-objective optimization (travel time versus emissions) (Chen and Yang, 2011)

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Following Research:

Stochastic user equilibrium and tradable credit scheme

(Sumalee et al., 2011)

Tradable credit schemes with external traffic (Marco Nie,

Agachai Sumalee; 2011)

Evolution of price and flow under a tradable credit scheme

(Ye and Yang, 2012)

Analysis and design of tradable credit schemes under

uncertainty (Shirmohammadi, Zangui, Yin and Nie, 2012)

Tradable emission credits for personal travel: a market-based

approach to achieve air quality standards (Aziz and

Ukkusuriy, 2012)

1 tradable travel credit schemes for network mobility management...

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