l3 intro transport planning

Introduction to Transport Planning

–Does anyone actually try to do this?

• Can we use our own experience to plan potential transport projects?

• Sometimes policies don’t have expected outcome.

• Important to model!

Transport Planning

Let’s explore with a greatly simplified example

Simplified Static Equilibrium Model

Braess’s Paradox (simplified example)

A

B

C

D

10

11

xc

10

44

xc 53 c

52 c

T=46 • y1+y2=T

• c1+c2=c3+c4

Equilibrium flows

• A-B-D (y1)

• Same as X1 here

• A-C-D (y2)

• Same as X4 here

2 Paths

y1=y2=23

c1+c2=c3+c4= 7.3 min

Braess’s Paradox Example

A

B

C

D

10

11

xc

10

44

xc 53 c

52 c

T=46 05 c

• A-B-D (y1)

• A-C-D (y2)

• A-B-C-D (y3)

3 Paths

1 2.3c

4 2.3c

Previously, 23 people took each path.

BUT, people realize they can

improve their travel time by

switching routes!

Braess’s Paradox Example

A

B

C

D

10

11

xc

10

44

xc 53 c

52 c

T=46 05 c

• A-B-D (y1)

• A-C-D (y2)

• A-B-C-D (y3)

3 Paths

y’1=y’2=0

c’1+c’5+c’4 = 9.2 min

y’3=46

6.41 c

6.44 c

Everyone switches!

Was previously 7.3 min. What happened?

1. Where do we get the trip demand (the T=46 from the example)?

2. How will land use impact demand?

3. How will congestion impact demand?

4. How do we represent the transport congestion?

Some transport planning issues already

Arising from this

The planning process is ever evolving with the role of governmental policies, technological innovations , and private interests.

Things to consider when planning:

1. What was the extent and technology of the transport system? - Steam engine, cars, elevators?

2. What were the pressing transportation concerns of the time?

3. Who had the responsibility for the planning, design and operation of transportation facilities

and services?

4. What direct and indirect government actions are the local, state and federal levels influenced

the development of the transport system and establishment of planning requirements?

Evolution of Planning

• State highway departments

• concerned with connectivity of intrastate and interstate highway network

• City traffic engineering departments

• concerned with accommodating the efficient and safe operation of the urban

street network

• City (or regional) planning departments

• concerned with regional land use planning, housing and urban public

transportation

Planning Entities and Roles

• Introduction of building codes

• Alleviate slums

• Minimize fire hazards, enhance living conditions

• Districting or Zoning

• Government power to regulate use of land

• Commercial, industrial, residential

• Parks movement

• Instigated by planners and landscape architects to improve city living conditions

• City-beautiful movement

• Improve aesthetics of public buildings, civic centres, parks, wide boulevards

• Public Transit and Decentralization

• Applied to both industrial and residential suburbs

Developments in Planning

These objectives required the help of civil engineers, and incorporations of

transport planners into the planning of urban development

Ebenezer Howard:

One of the great guides to the town planning movement. Introduced Garden City.

Garden City:

Idealized utopian city in which people live harmoniously together with nature. Many garden city principles are being used in modern town planning.

Planned, self-contained communities surrounded by “greenbelts”, containing proportionate areas, of residences, industry and agriculture.

Example: Garden Cities Ebenezer Howard

What sort of transport problems do we deal with?

A small sampling include:

– Robust Systems

• How to design a transportation network that minimizes system performance deviation as demand or capacity levels vary

– Network Design

• How to create/modify a network

– Network-wide flows

• How do many people simultaneously making route choices impact one another?

• This is a type of “game” (Nash Equilibrium)

Network Terminology

Nodes are often associated with some aspect of travel demand

– Can be intersection, parking lot, port, etc. (a point entity)

– Travellers want to move from some origin node to another destination node

Links are often associated with measurements of congestion

– Can be a road or other means of travelling between nodes (an association entity)

– The more travellers on a particular link, the higher the congestion

– Congestion can be represented as a function of the # of travellers

Node

Link

Node

Networks are a simplification of the transport system into nodes and links

Simple Network

A

C

B D

E

F

G

5

3

4

1

6

3

2

3

Less Simple Network

Example Network Representation

What all is involved in the transport planning

process?

Survey Existing

Conditions and

Trends

Define Goals and

Objectives

Identify problems

Generate Alternatives

Evaluate Alternatives

A rational model for the long-

range transportation planning

process

Planning studies are intended to model and estimate travel, economic, social and environmental factors that are important in the transport planning process

Initially, highway network extensions were based on “anticipated future travel demands”, computed by projecting current traffic measurements using population and economic growth factors (i.e., GNP).

• Requirements could be checked against available capacity, and improvements scheduled accordingly.

Urban travel necessitated more refined techniques. Mainly due to the existence of multiple available routes between parts of the city. Required introduction of :

• Travel demand forecasts

• Land use models

• Urban travel surveys

Planning Studies

• Initially inter-zonal trips distributions for a target year were approximated using simple growth factors to base year travel volumes.

• Became evident that demand for added capacity and parking facilities was not uniformly distributed throughout urban areas

– Dependent on type (residential, commercial, industrial) and intensity (residential

density, workers per acre, shopping floor space, etc) of land use in each zone

• Furthermore, regional growth was unevenly distributed among zones because of differences in

– Availability and suitability of developable land

– Urban planning policies (i.e., zoning)

– Accessibility

Travel-Demand Forecasts

Trip generation models to relate trip-producing capability of residential areas and trip-attracting

potential of various non-residential types of land-use classes were postulated, calibrated and validated.

How is a region divided up amongst the available land use sectors? Initially developed to provide inputs to the travel demand forecasting models.

Assume three region sectors:

1) Industrial activities producing goods and services (mainly for export) Location is independent of population

2) Non-industrial activities (i.e. retail) which serve the needs of the population

– Locations must follow residential markets

3) Population

Example – Lowry Model: Given a region sub-divided into analysis zones, models assigns sectors to regions to meet constraints imposed by land use policies (max number of houses in a zone, etc).

• Start by exogenously assigning basic employment locations (may rely on zoning or land availability). Then distributes population to meet labour needs (using gravity model), and assigns activities needed to support population needs.

Land-Use Models

• Conducted to collect information about household’s travel behaviours (socio-demographic characteristics, information on number of household trips made, distances travelled, travel mode used, etc)

• Origin and destination (O-D) surveys

• *Home interviews

• Truck interviews

• Taxi interviews

• Parking surveys

• Considered 4-5% of the households in a region

• Use statistical techniques to expand behavioural assumptions to entire population

• Validate results (of statistical methods) using traffic counts

Urban Travel Surveys

Travel-Demand Forecasting Process

Trip Generation

Trip Distribution

Mode Split

Transportation

Network & Service

Attributes

Link & O-D Flows,

Times, Costs, etc.

Trip Assignment

Population & Employment Forecasts

Demand Related Components

General Framework of 4-Step Models

Route Choice Modelling

Map is defined a priori

• Zone boundaries defined

• Based on survey data

• Zone land use quantified

• Zone centroids created

Transport network overlaid

• Centroids connected to network

Generate Number of Trips:

• TO each zone (Attractions)

• FROM each zone (Productions)

• Function of Land Use and socio-

demographics in each zone

Define Network and Travel Demands

Will this network remain fixed

throughout the planning process?

Heterogeneous individuals with

different socio-demographic

attributes, but for simplicity we

assume that they have homogenous

travel attributes


~1500 inhabitants in Census Blocks

<3000 inhabitants in TAZs

~4000 inhabitants in Census Tracts

County

City

State


Important Note: How trips are

distributed is still independent of the

heterogeneous attributes of individuals

From the N

number of

trips coming

in


Important Note: How trips are

distributed is still independent of the

heterogeneous attributes of individuals

From the M

number of

trips going

out:


For each link/path:

• What is the demand?

• What is the level of service?

• If it is congested how it can

be fixed?

Consider all trips using a link/path


Trip Generation

Trip Distribution

Mode Split

Trip Assignment

I

Oi

J

Dj

Trip Generation

I J

Trip Distribution

Tij

I J Mode Split

Tij,auto

Tij,transit

I

J

Trip Assignment

-- path of flow Tij,auto

through the auto

network

General Framework of 4-Step Models


Questions?

l3 intro transport planning

Documents

cd y2

bd y1

planning process

transport planning issues

regional planning departments

town planning movement

regional land use planning

modern town planning