1. Transport Systems and Planning

1.1 The Importance of Transport

• Transport an integral part of human culture in all societies
• People wish to transport: people (individually or in mass), things (freight), and information.

Information transfer is now relatively fast and efficient.

Transport of things can be dictated as to how and when they travel.

People want to exercise control over their travel.

1.2 The Development of Transport

Stages of Development:

Human Powered

Animal Powered

Machine Powered

An alternative method of thinking of the development of transport is:

Primitive (vehicle found in nature)

Transitional (improved vehicle)

Advanced (the 'way' improved)

Chronologically transport development started with basic land and water transport where motive power was provided by the human. Land transport developed to using other animals as beasts of burden - horses, camels, etc. Further development occured with the invention of devices to attach to the animal - sleds, carts, etc. A major step forward occurred with the invention of the wheel, although the development of wheeled vehicles was fairly slow.Water transport developed with the use of devices to carry the person - canoe type structures, where the power was still provided by the human. The development of the sail allowed the use of an external power - the wind. The use of sail transport was limited by navigation restrictions (the necessity to be in sight of land) and the inability to sail against the wind. The technique of sailing against the wind developed in the mid 1400's with the development of multi-masted vessels.

A major impetus to the development of transport occur with the industrial revolution and particularly the harnessing of steam power. This led to the development of the railway in the early 1800's and a worldwide boom in railway construction occurred between about 1830 and 1900. Steam power also led to the development of steam ships and a move away from sailing ships. The development of the motor vehicle in the late 1800's and early 1900's started the decline in railway building and rail transport. However, at the turn of the century it was by no means clear as to which way road transport would develop with steam, electric and internal combustion engine powered vehicles all being used. The internal combustion engine was to win out for road transport, and its relative compactness and lightness also led to its use in the development of aircraft.

LINK TO THE PICTURE GALLERY

The Picture Gallery contains some photographs of The Development of Transport .

LINKS TO SITES ON TRANSPORT DEVELOPMENT:

The Smithsonian Institute in the USA provides some overview of transport development, particularly in the last one hundred years, through its Transportation History page.

1.3 Transport in the Modern World

The major factors influencing the development of transport on a global basis are:

• The Pattern of Trading Nations. This is a complex factor. There is a growing tendency for nations to associate in trading blocks and this increases the mutual interdependence of nations.
• The Growth of Population. Estimated world population figures are:

Year	Estimated World Population (Millions)
1650	450
1900	2000
1960	3000
1980	4000
2000	6100
2020	7700
2040	8800

• The Increasing Affluence of Nations.
• The Decline in Strategic Interferences with Transport.
• The Search for Increasing Efficiency in Transport.
• Environmental Concerns. Including noise, air pollution, and safety.

Transport can be considered to have three major roles in modern society:

• Economic - Economic wellbeing is dependent on adequate transport facilities.
• Social - Transport provides for the interaction of persons, and the provision of goods and services.
• Political - Transport influences trading, which in turn influences sovereignty.

1.4 Transport / Land Use Interaction.

Transport and land use are closely related.

Can be considered in the following way:

New transport facilities results in increased accessibility, which results in land values increasing, which results in a change of land use to a higher use, which results in increased trip generation, which results in greater demand for transport services, which results in new transport facilities (back to the beginning).(i.e. a cyclic process)

This is analogous to the old problem: Which came first - the chicken or the egg? In this case, which comes first: Change to land use or change to the transport system?

1.5 Transport Planning.

Transport planning: the methodical process of preparing physical facilities and services for all modes of transport for future transport needs.

1.6 Transport Models.

Detailed transport planning depends on the use of complex mathematical models of the transport system. These models are simplified representations of the real world. They are used to explore the consequences of particular transport policies or strategies.

The ideal model is one which produces accurate forecasts at minimum cost.

A critical decision in creating a transport model is deciding which parameters to include and which parameters to ignore. The inclusion of the most relevant parameters will optimise the accuracy of the predictions obtained from the model. However it is always a difficult task to know which are the key parameters in a particular situation. The accuracy of a model may be improved by the inclusion of more parameters but this is usually at a greater financial cost in creating and running the model.

The transport modelling process consists of the following steps:

• Definition of study area and creation of internal and external zones
• Data collection
• Forecast of parameters (eg land use)
• Preparation of mathematical model
• Calibration of model
• Modelling
• Evaluation of results and production of a physical plan.

• trip generation,
• trip distribution,
• modal choice, and
• traffic assignment.

LINKS TO SITES ON TRANSPORT MODELLING.

2.3 Survey Area

The study area is defined by an external cordon. The area within the study area is then broken down into internal zones. External zones are created for travel from the study area to outer destinations. External zones will usually be much larger than internal zones.

Zones should be established so that they are compatible with the zones used in other relevant data collection exercises for the area (for example population data from census collection). Zones should be relatively uniform in land use, fairly uniform and regular in shape, and large enough to use for a statistically reliable sample.

2.4 Data Collection

Census data often provides cross-sectional data on characteristics such as population distribution and age characteristics. Home interview surveys will also frequently be used in transport studies to supplement census data and to obtain specific data on travel characteristics. Home interview surveys generally sample about 5 to 20 % of households and obtain data on general household characteristics (eg number of motor vehicles in the household), characteristics of individual household members (eg age, drivers licence holding or not, etc) and/or particulars of individual trips.

2.5 Forecasts of Future Planning Parameters

• population,
• income distribution, and
• the spatial location of land use.

2.6 Trip Generation

Each trip has an origin and a destination.

Transport modelling studies usually consider trips in two broad categories:

• Home-based (any trip having either the origin or the destination of the trip as the home), and
• Non-home based (any trip having neither the trip origin nor the trip destination as the home).

The two methods which are commonly used to build trip generation sub-models are:

• Multiple linear regression, and
• Category analysis.

2.7 Trip Distribution

In mathematical terms, the trip generation sub-model will give a prediction of the total trips generated from zone i (Pi), and the total trips attracted to zone j (Aj). The trip distribution sub-model then allows the prediction of the interzonal trips between zones i and j (Tij).

The methods used for trip distribution fall into two groups:

• Growth Factor Methods, which include:
• The Constant Factor Method,
• The Average Factor Method,
• The Fratar Method, and
• The Furness Method.
• Synthetic Methods, of which the most widely used is the Gravity Method.

2.8 Modal Choice

The factors affecting a person's choice of mode are numerous. The variables which are usually incorporated into a mode choice model are:

• tripmaker characteristics - represented by factors such as car ownership, income, and net residential density.
• trip characteristics - usually considered by establishing differing modal split relationships for different trip types e.g. home-work trips, home-school trips, etc.
• system characteristics - generally evaluated by considering the cost of travel including time cost.

2.9 Traffic Assignment

Traffic assignment is usually confined to road traffic as most other modes (except perhaps walking and cycling) are limited to a particular route.

The basis of assignment is usually travel time, and as future trips are assigned to the network travel times can be expected to vary.

In the traffic assignment process it is not unusual to find that the proposed road network becomes overloaded and that some car trips may need to be restrained.

There are four common methods of traffic assignment:

• all-or-nothing assignment;
• assignment by the use of diversion curves;
• capacity restrained assignment; and
• multipath proportional assignment.

2.10 Evaluation

• Numerical evaluation. This is to confirm the computational validity of the results. Two main sources of error which occur are programming errors (i.e. errors in the computational algorithms used) and input information errors.
• Operational evaluation. This is to confirm that the predictions made, and solutions adapted, are physically achievable in the real world. Types of problems which occur include the fact that modelling is usually done with 24 hour flows but the network needs to be able to cope with peak period flows, and traffic assignment may tend to leave some links very heavily loaded while other alternate links have light flows predicted.
• Environmental evaluation. Any proposed transport change must be perceived by the community as being acceptable, or at least more acceptable than any alternative.
• Economic evaluation.The final stage of the evaluation process is commonly known as cost-benefit analysis or economic evaluation. The basic approach to economic evaluation is to compare the expected benefits with the cost of making and operating any change.

2.11 Trends in Transport Planning

In the 1950's and 1960's most transport plans used large household interview surveys to gather travel data, used the conventional four-step transport planning model (trip generation, trip distribution, modal split and traffic assignment), and produced a transport plan for some distant planning horizon (usually 20 years). The results of the models were criticised on many grounds, including that the process was cumbersome and expensive, the process produced only one plan for some distant year, the modelling procedures were unresponsive to policy needs or changes, and the process tended to rely too much on historical data rather than being based on a true understanding of travel behaviour.

In the late 1960's researchers started to model transport demand based on behavioural factors. This required consideration of individual travellers, or a "disaggregate" approach.

In the 1970's research into travel behaviour increased substantially. In the late 1970's papers on 'activity analysis' appeared. Activity analysis sees travel as but one type of human activity.

In the 1980's research tended to focus on dynamic analysis of travel behaviour which focuses on looking at changes in travel behaviour (which requires longitudinal time series data rather than the more common cross-sectional data).

The rapid increase in the power of microcomputers has meant that transport modelling has tended to shift away from main-frame computers to microcomputers.

Major directions in recent planning has been the better utilisation of existing facilities, the use by governments of private sector finance for the the construction and operation of new facilities, the introduction of user pays systems such as road pricing, and the use of integrated planning.

LINKS TO SITES ON TRANSPORT PLANNING.

2.12 Microcomputer Traffic Systems Design Models

Four broad categories of models used in Australia can be identified:

• Macro-models (or macroscopic analytical models) - software packages include EMME, CUBE and VISSUM.
• Micro-models (or microscopic analytical models) - packages include SIDRA, INTERSECTION and ARCADY.
• Macrosimulation models - packages include TRANSYT and SATURN.
• Microsimulation models - packages include AIMSUN, PARAMICS, VISSIM and SIDRA TRIP>

LINKS TO SITES ON MICROCOMPUTER TRAFFIC SYSTEMS DESIGN MODELS.

The EMME package is marketed by INRO , a Canadian firm, and a description of the product is available by accessing their site. The software comes in different sizes with the smallest size handling a maximum of 250 zones, and the largest size handling a maximum of 4000 zones.

The SIDRA (Signalised Intersection Design Research Aid) was developed under the guidance of Dr Rahmi Akcelik when he was at the Australian Road Research Board in Victoria. The product has been further developed and the Web site gives a good description of the product.

Page last modified 28 June 2010.