Links to: |
CIV3703 Transport Engineering Overview |
Ron Ayers Homepage |
Faculty Homepage |
USQ Homepage |
A basic need of any society is a transport system which can provide for the effective, efficient and safe movement of goods and people. As the number of people in a society changes the required amount of transport will also change. As the nature of a society changes, for example the level of industrialisation of the society increases, it is found that the type of industry development changes from primary industries to secondary and tertiary industries and this again changes the demands on transport. As the level of wealth of people in a society changes their demand for transport services will also change.
A continually changing demand for transport and transport systems with time therefore occurs in all societies. This means the provision of transport systems in a society will also be in a continual state of flux to cater for the changes occurring in the society. Changes to a transport system usually do not come at zero cost and therefore the society, or people in the society, have to decide how much change in the transport system is tolerable in regard to affordability. The area of transport economics therefore impacts on all that we do in planning and operating our transport system. Changes in the transport system will also create impacts on the physical environment and the consumption of energy by the transport system. The areas of environment impact and energy usage also impact heavily on the development and operation of the transport system. This module looks at the areas of transport economics, environment impact and transport energy usage before completing the course with considerations of transport sustainability and the future of transport.People all over the world must use the earth’s natural resources to satisfy the necessities of life – food, clothing and shelter. In addition, people will often seek items beyond the necessities in order to make life more pleasant, comfortable or rewarding. The natural resources of the earth are not uniformly distributed and therefore transport is required to bring the resources to people, or to bring people to the resources. As well, people will transport in order to bring services to others or to seek services e.g. medical services.
Economics is primarily concerned with the production, distribution and consumption of goods and services which are of value to people.
Economists conveniently divide the broad area of economics into two main streams:
Transport engineers generally work in the microeconomic area because they are involved in the detailed planning, construction and maintenance of specific transport projects. These projects all lead to small savings in economic resources which generate microeconomic benefits and an increase in the welfare of the community. However it should be noted that the sum total of the microeconomic effects of individual transport projects will impact on macroeconomic factors such as infrastructure spending and employment.
The demand for goods and services depends largely upon consumer income and the price of the particular good or service relative to other prices. For example the market for expensive luxury cars is fairly restricted as only a small number of people in society have an income large enough to consider the purchase of such an item, particularly when lower priced cars will still fulfil the requirement of getting the motorist from one point to another.
In a more general way, the demand for travel will depend on the income of the traveller. The choice of travel mode depends on several factors such as the purpose of the trip, the distance to be travelled and the income of the traveller.
A demand function for a particular product represents the willingness of consumers to purchase the product at alternative prices. A demand function shows, for example, a number of passengers willing to use a bus service at difference price levels between a pair of origins and destinations, for a specific trip, during a given period.
The term price represents all the perceived outlays that the traveller will have to make for a given trip. This would include the cost of the fare, but would also include the cost of travel time, comfort, safety, reliability. The fare of course is a tangible cost but several of these other factors are intangibles. Most of the components of the perceived price for travel are measured and expressed in monetary units. This synthetic ‘price’ is sometimes called a generalised price.
A knowledge of the functional form of travel demand can be used to forecast changes in the volume of travel caused by specific changes in price in the short run.
A useful description for explaining the degree of sensitivity to a change in price (or some other factor) is the elasticity of demand. The elasticity of demand is the percentage change in quantity of trips demanded which accompanies a 1% change in price.
If for example a 1% increase in the price of bus trips results in a 5% decrease in the number of trips, the elasticity of demand for trips is 5.0.
When the elasticity is greater than 1 the demand is described as being elastic, meaning that the resulting percentage change in quantity of trip making will be larger than the percentage change in price. In this case demand is relatively sensitive to price change. However, when the elasticity is between 0 and 1, the demand is described as being inelastic or relatively insensitive.
Consumer surplus is a measure of the monetary value made available to consumers by the existence of a facility. It is defined as the difference between what consumers might be willing to pay for a service and what they actually pay. For example a commuter may pay $3 per trip, but may be willing to pay up to $4 per trip. In this case the consumer surplus would be $1.
In general, a transport improvement can be measured in terms of the change in consumer’s surplus.
It is essential to have a knowledge of costs, or the value of a product or service.
Fixed costs are inescapable costs which do not vary with the quantity of production. For example if we are operating a fast food restaurant we will have fixed costs of rent, hire or lease of equipment, etc. which will have to be met whether we sell one hamburger or 10000 hamburgers. However the fixed cost per unit of production will decrease with the more units produced.
Variable costs, on the other hand, increase with output or production. For example we use 1000 times more meat in 1000 hamburgers than we use in one. However if it costs us $0.50 in labour and heating to cook one hamburger, it may only cost $0.47 per hamburger for the production of two, or $0.42 per hamburger for one hundred.
The total cost of production is the sum of the fixed and variable costs and will increase with production. For any particular level of production, the average cost per single unit can be found by dividing the total cost for that level of production by the number of units produced.
The marginal cost of a product is defined as the additional cost associated with the production of an additional unit of output. This is an important concept.
Pricing is a method of resource allocation.
There is no such thing as the ‘right’ price but rather there are optimal pricing strategies which permit specified goals to be obtained. The optimal price, for example, to achieve profit maximisation (say for a private bus operator) may differ from that needed to maximise welfare (e.g. for a government operated bus service) or to ensure the highest sales revenue. In some cases there is no attempt to set a price which maximises or minimises anything, but rather prices are set that permit some other objectives to be achieved (e.g. security, minimum market share, etc.).
Further, prices may be set to achieve certain objectives for the transport supplier’s welfare, while in other fields prices may be set to improve the welfare of consumers.
One of the major problems in discussing pricing policies in practice is to decide what exactly the objective is. Profit maximisation is the traditional motivation of private enterprise undertakings. The actual price level in this case depends upon the degree of competition in the market. Where competition is high, then no single supplier has any control over price and must charge that determined by the interaction of supply and demand in the market as a whole. Within such a competitive environment it is impossible for a supplier to make super-normal profits in the long run because if super-normal profits exist, other competitors will enter the market and increase overall supply.
In contrast, if a transport supplier has a monopoly on the supply of services, and has no fear of new entrants increasing supply, then prices can be set at any level the supplier desires, or the supplier can specify what level of service is to be provided.
However there are few natural monopolies in transport. Modes are normally competitive even if they have a tendency towards a monopoly. Also users of transport services often have the alternative of either changing their method of production (in the case of freight transport) or pattern of consumption (in the case of passenger transport), so that transport is itself competitive with different forms of human activity.
Welfare economics takes a wider view of pricing, looking upon price as a method of resource allocation which maximises the welfare of the society rather than simply the welfare of the supplier. In some cases, when the good or service is provided by a public agency, the supplier’s welfare and social welfare will be the same thing. In other instances controls or incentives may be applied to private companies so that their pricing policy is modified to maximise social rather than private welfare.
One of the most important forms of transport infrastructure in Australia, as in most countries, is the road system. The pricing problems that have been alluded to in the previous section can be illustrated by examining some of the main issues involved in charging for road space.
In Australia no direct charge is usually made for using a public road, although motorists are required to pay tolls on a small number of expressways, motorways and bridges. Road space is thus provided ‘free’ in most circumstances. However road users can be said to contribute towards the cost of roads via fuel levies and other motoring charges such as licence and registration fees.
Consider some figures for 1994/95. Governments in Australia (predominantly the Federal Government) raised $9494 million in taxes on fuel. Another $4183 million was raised through taxes based on vehicle ownership of vehicles (as distinct from the amount of their use). A total of $15 588 million was raised as revenue from road users.
The total expenditure on roads was $5707 million, and the difference (approx. $9900 million went into consolidated revenue (i.e. was spent on other Government spending initiatives not roads). It is this differential between revenue collected and funds spent which gives rise to a lot of argument from the motoring public, motoring organisations, state and local highway authorities, and other groups.
The other method of charging for road use is via direct user charges whereby the actual ‘time’ or ‘distance’ of vehicle travel is monitored and charged. Traditional toll collection consists of payment at a point or barrier for entry onto a facility (e.g. road, bridge or tunnel). Developments in direct charging include the use of electronic systems using fixed beacons and on-vehicle transponders. Many road authorities are now considering charging not only for special purpose facilities (e.g. toll roads and harbour tunnels) but also for use of the normal road system, particularly in areas subject to traffic congestion. The concept is that with a limited supply of physical resources, the only realistic option is some form of traffic restraint and stricter management of actual traffic demand. This is best achieved through using effective pricing mechanisms in order to attain better utilisation of the existing road space.
Another issue associated with road funding has received a significant amount of attention in recent years. This is the issue of the contribution made by different categories of road users, and in particular whether heavy vehicles pay their fair share for road use. From engineering considerations there is no doubt that heavy vehicles result in increased road costs through their damaging effects. It has been argued that there is a case for increased taxation of road vehicles and that such taxation should be directly related to the damage being caused to the road.
Although it may be possible to reach consensus that a relationship should exist between the taxing of commercial vehicles and the extent of costs which have to be borne by public authorities in maintaining roads, the problem of deciding on the basis of allocating those costs between different types of vehicles and scales of operation remains extremely difficult. The importance of devising an equitable basis of allocation increases as the move to allow heavier goods vehicles gains political momentum.
However, it may also be considered that no vehicles ‘cause’ road expenditure. Rather, they have an effect on design standards and maintenance which is a response to their effect. Therefore to burden heavy transport operators with charges above those of other road users is unfair, as road authorities have as their charter to provide safe and trafficable roads for all road users.
Both the overall funding and heavy vehicle issues tend to be argued largely from the point of view of cost recovery, i.e. the road user generally, or truck operator in particular, paying for the use of government provided roads.
In addition to direct impacts on the environment there can also be upstream and downstream effects. An example of an upstream effect is the emissions from coal-fired power stations producing the electricity to run trains. A downstream effect might be the damage to bushland and waterways from dumping old cars, oil and tyres. In other words, some of the environmental degradation caused by transport takes place outside the area of the transport system.
Loudness
The loudness or intensity of sound is directly related
to the amplitude of the pressure fluctuations transmitted through the air.
The pressure fluctuations cause the ear drum to be flexed and thereby create
the sensation of sound. The ear can sense pressure fluctuations as low as
50 micro Pa (the threshold of hearing) and up to about 5 Pa which is considered
the threshold of pain.
This large range of pressure fluctuation is clumsy
to use in reporting. In addition, as a protective mechanism, the auditory
response is not linearly related to pressure fluctuation. To overcome these
difficulties another unit is used to describe loudness – the decibel (dB).
In outdoor situations a change of 3 dB is required to be noticeable. A change
of 10 dB is generally perceived to be a doubling of the sound level.
Frequency
The human ear can hear a large range of frequencies,
or changes in the rate of pressure fluctuations in the air. The pressure
changes per second, or oscillation per second, have the unit of hertz (Hz).
The ear can detect a range of frequencies from about 20 Hz to 20,000 Hz.
However, not all frequencies are heard equally well with low frequencies
(less than 500 Hz) and high frequencies (greater than 10,000 Hz) being more
difficult to hear.
Duration
A gunshot may be loud but it only lasts a fraction
of a second. Road traffic noise may not be as intense but it is continual.
Therefore measures have been developed to describe how sound varies with
time.
Subjectivity
Individuals have different responses to various sounds.
What one person perceives as music another person may regard as a noise. Unwanted
sound is commonly referred to as noise. Transport noise is a common problem
in urban areas. Noise annoyance is a subjective thing and criteria for noise
control are usually based on attitudinal surveys.
Single loud noises may result in hearing loss and
these noises may need to be controlled from a community viewpoint. However
transport noise is usually of a longer duration and not as loud. Short term
effects are likely to be annoyance or irritation. Transport noise can lead
to problems in emotional well being and cause increased tension by interfering
with sleep patterns or causing disruption to the routines of daily life.
Long term exposure may result in reduced hearing ability.
Noise is generated by the engine and exhaust systems of vehicles, by aerodynamic friction, and by the interaction between the vehicle and its support system (e.g. tyre-pavement interaction for road vehicles and wheel-rail interaction for railway vehicles). Insulation in the engine compartment is used to reduce engine noise, mufflers are used for exhaust noise and pavement type selection may reduce tyre/pavement noise production for road traffic.
The path may also be altered to reduce noise. Increased distance between the source and the receiver results in reduced sound levels due to geometric spreading. It therefore follows that increased path distance results in traffic noise abatement. This abatement measure may be a possibility if sufficient right-of-way widths are available. However the establishment of a green-belt between source and receiver may be a very costly exercise in an urban area.
A more common strategy for noise abatement in urban areas is the use of noise barriers. The barrier is designed so as to reflect and diffract the sound. The difference in noise levels with and without the wall is referred to as insertion loss. Although vegetation is sometimes used as a noise barrier, it is generally found that a more solid, fabricated structure is most effective in noise amelioration.
In some cases it is not practical to mitigate noise in the path e.g. near airports. In these cases it may be possible to improve the situation by insulating the buildings. Measures which can be used include increased insulation of walls and roof, double-glazed windows, acoustic vents and storm doors. These measure are frequently used near large airports, and to protect buildings such as schools near busy roads.
The combustion of fossil fuels for transport use results in the release of several contaminants including carbon monoxide, carbon dioxide, hydrocarbons, oxides of nitrogen, and lead and other particulate matter. Hydrocarbons are the result of the incomplete combustion of the fuel. Particulates are minute particles that are suspended in the atmosphere and include aerosols, smoke and dust particles.
Once emitted into the atmosphere, air pollutants undergo mixing or diffusion, the degree of which depends on topographic, climatic and meteorological conditions. Other pollutants not directly emitted from the source may form in the atmosphere using the directly emitted pollutants as feed material. These include nitrates, sulphates and photochemical oxidants (ozone). Photochemical smog is the result of complex chemical reactions of the oxides of nitrogen and hydrocarbons in the presence of sunlight.
Air pollution can be associated with respiratory damage in humans (bronchitis, emphysema, pneumonia and lung cancer) as well as eye, nose and throat irritations. Societal effects include damage to structures and materials, damage to crops and animals, and atmospheric haze. Global effects from acid rain, global warming and ozone depletion are also of concern.
Fossil fuel combustion, particularly by motor vehicles has been identified as the largest single contributor to atmospheric pollution, particularly in urban areas. Judgement about this must be tempered by the fact that motor vehicles are responsible for most of the urban passenger task and virtually all the urban freight task.
The importance of transport pollution must also be considered in the context of air pollution as a whole. For instance, although cars have higher rates of carbon dioxide emissions per passenger kilometre than buses and rail, motor vehicles contribute less than 25% of total carbon dioxide emissions. The bulk of carbon dioxide emissions come from coal-fired power stations which are usually located well clear of major urban areas. They do however provide the motive power for urban rail services.
The rate of emission and the concentration of particular pollutants is also affected by the speed of road vehicles. Emissions increase markedly when vehicles accelerate and are low when they are idling. The impact of congestion on pollution levels is a complex question but it is widely accepted that traffic congestion increases local air pollution.
Pollution levels at a location vary considerably depending upon the type of vehicle operation, the time of day and the atmospheric conditions. In some cities the peak condition for carbon monoxide concentration follows very closely the chronological sequence of peak-hour vehicle operations, but in other cities this relationship does not occur. Vehicle age is a factor in the level of pollution, primarily because of innovations in anti- pollution equipment.
In addition to these considerations, other ecological considerations are required. Coastal zone management must be considered if the project is located near a coastline. The effects on agricultural production must be considered if the project goes through or is adjacent to arable land. If the project is in a floodplain special considerations will be required. It becomes apparent that ecological impacts are very important and that many players will need to be involved during the planning stage.
The requirements for environmental documentation vary depending upon the different legislative and procedural arrangements adopted by differing governments. Most however have the following common features:
It is now usual for the public to be involved in the basic decision-making process. Involvement of the public from an early stage is desirable in order to minimise major conflict after a project is committed or has reached a stage where modification is difficult. The essential aspect is that public comment should be initiated before a commitment is made to the project so that it is publicly evident that comments have the potential to influence the course of the project.
The evaluation of EIA documents is carried out by the appropriate authorities both as an aid to government decision making and to enable the identification of any environmental conditions which need to form part of the approval.
Subsequently it was found that some of the energy from the sun that had been absorbed by growing plants was retained when the plants died. The dead vegetation was transformed over a long period of time into fossil fuels such as coal and oil. Developments in the Industrial Revolution showed that these fuels could be utilised to provide motive power via steam and internal combustion engines.
Throughout the twentieth century the majority of the world’s population has become dependent on the use of fossil fuels to keep industry and communication going. Transport in particular has come to rely almost exclusively on liquid fuels derived from crude oil. This is because these liquid fuels are convenient and economical to use, and because their energy content (in terms of energy per unit mass of fuel) is much higher than alternative fuels.
However, the fuels on which we currently place so much reliance are nonrenewable and are being rapidly depleted. There is therefore a need for society to conserve energy, to develop alternative energy technologies, to increase the efficiencies of various components of society’s infrastructure (particularly transport), and to improve its understanding of energy issues.
Spatial structure refers to the order and relationship among physical elements and land uses. This structure evolves over time from the interaction among individuals, households, firms and institutions. Land use planning generally uses a prescriptive approach in deciding what future spatial structure should be developed. This prescription is based on a land-use arrangement that is most efficient and least costly to government and its citizens, considering elements such as health, safety, convenience, environmental quality, social equity and social choice. In recent times, studies relating to energy-efficient patterns of land development have assumed importance.
Energy efficiency is a special case of cost efficiency. The transport sector is a heavy consumer of fuel, and it can be concluded that land-use alternatives which minimise travel are usually fairly energy efficient solutions in the use of land. Another consideration is the development intensity which is used for land. For example a city that suffers from urban sprawl and ribbon development will have more kilometres of streets and services (water pipes, sewer pipes, electricity cables, etc.) than would a more compact city. In this case initial development costs will be higher, but so will the cost of ongoing maintenance and replacement. In reality, the crucial issue is the costs the citizens are willing to pay in order to satisfy their wants. This willingness to pay is a function of a society’s values, attitudes, and preferences.
Energy Demand
Energy use may be thought of as occurring in four basic sectors: transport, residential, commercial and industrial. Transport accounts for a significant proportion of total energy use in most industrialised countries. Public policy in Australia has been to provide relatively cheap energy and social, community and industrial development has progressed on this premise from the end of World War II (1945) until recent times. This has been one factor that has contributed to urban expansion in Australia. Other factors include rapid increase in real per capita income, rapid diffusion of the car, development of the major road system in preference to the development of public transport, and land-use planning policies which have encouraged low-density residential development. However changes in factors such as the decline of household size, new environmental controls and energy policy are now occurring which could change this pattern in the future. Transport uses about 30% of the energy used in Australia. About one third of that (10% of the total) fuels urban car travel. If the urban car usage could be halved some increase in public transport energy usage would occur, but an overall reduction of about 3% of national energy use may be possible. This is just one way in which our national energy use could perhaps be reduced. The challenge is for society to be willing to tackle the hard decisions involved in reforming our energy usage.
A major area for potential saving is the transport sector. A great deal of investigation and research has been carried out in recent times to consider ways in which transport energy usage may be reduced. The solutions proposed are quite varied, and the following presents just a few of the ideas which have been investigated or are being implemented:
Environmental Principles for Engineers (Institution of Engineers, Australia 1992) expands on this description to make it more applicable to the broad scope of engineering works. Important issues with respect to transport planning are:
Economic, environmental and social sustainability are often mutually reinforcing. Road or public transport systems that fall into disrepair because they are economically unsustainable fail to serve the needs of the poor and often have environmentally damaging consequences. Hence, the three types of sustainability are closely linked and a policy on sustainable transport must therefore consider all three aspects in order to be comprehensive and effective.
The term ‘transport futures’, for some people, will
conjure up visions of spaceships and high speed trains, rocket belts and
flying cars, i.e. advanced transport technology. However while advanced technology
will certainly be a part of transport’s future, there are other factors which
will greatly influence the transport of tomorrow. For example, the interaction
between transport and land use plays a major role in determining the demand
for travel and the viability of modes of travel.
But in many respects the development of the motor vehicle has worked to society’s disadvantage. When motor vehicles were scarce their effects were minimal. As numbers increased so did the problems of road accidents, congestion, air pollution and noise. More insidious consequences of mass car-ownership have been the effects on public transport and the structure of towns. The growth in the proportion of trips by car is mirrored by the corresponding decline in trips by public transport. The effect on the structure of towns is shown particularly in the pressure for new developments on the periphery of urban areas. An unknown in this situation is whether large-scale peri-urban development, and the roads and parking areas which serve them, actually induce more trips to be made. The need to provide a road network to cope with increasing vehicle numbers has also severed many older neighbourhoods. People who cannot drive because of financial or physical limitations now find their access to life’s opportunities seriously impaired and society has divided into the transport ‘haves’ and ‘have nots’.
Above all, mass use of cars has placed a tremendous burden on the world’s liquid energy resources. More than half of the petroleum produced in the world today is used for transport purposes, and about 80% of that is for cars. However, the possibility of reducing society’s reliance on the private car appears small. Most people in developed countries seek to be able to have the freedom of movement associated with individual car ownership and the concept of universal car ownership is not impossible. Very many in the poorer countries of the world aspire to this as well, and car ownership in these countries is often increasing at a much greater rate than population increase. Currently global car ownership works out at about 100 cars per 1000 population and this is expected to grow to about 120 cars per 1000 population by the year 2010. However rates in countries such as the USA and Australia are about 600 cars per 1000 population and only slight increases in this level are likely to occur. The bulk of the increase in total vehicle population (from about 550 million now to about 800 million by 2010) will occur in the rapidly developing countries of the world.
Suburbanisation of our cities and towns has made the car an essential component of daily life in all areas except the central cores of our largest cities. Individually, people rely on their cars and cherish the freedom, convenience and instant mobility that it provides. Collectively, however, their attachment to the car has created conditions that increasingly threaten to compromise the independence they value. Over the last two decades governments have become increasingly aware of the cost to society of large scale dependence on the car and have begun to formulate policies to met the challenges created by continued high levels of car usage. These policies have included:
But what of the other 20%? People do not use cars only for commuting. They are also used for the 5000 km annual holiday and the like. Unfortunately we have grown up with the concept that the one vehicle is suitable for all trip purposes when of course it is not. It may be that in the future all purpose cars are not able to be sanctioned by society and more specialised vehicles are developed and used.
The essence of IVHS as it relates to transport operations is the improved ability to manage services using accurate, real time information and hence to greatly enhance the control of traffic flow and individual vehicles.
Six broad and interrelated categories can be identified in the area of ITS.
The National Transportation Library in the USA contains an area on Intelligent Transport Systems which continually adds new material on the latest developments in ITS.
Page last modified 28 June 2010.