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Fundamentals of

Transportation

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Fundamentals of Transportation

2

Fundamentals of Transportation

Fundamentals of Transportation

/About/

/Introduction/

/Economics/

/Geography and Networks/

/Planning/

/Trip Generation/

/Destination Choice/

/Mode Choice/

/Route Choice/

/Evaluation/

/Operations/

/Queueing/

/Traffic Flow/

/Queueing and Traffic Flow/

/Shockwaves/

/Traffic Signals/

/Design/

/Sight Distance/

/Grade/

/Earthwork/

/Horizontal Curves/

/Vertical Curves/

Other Topics

/Pricing/

/Conclusions/

/Analogs/

/Decision Making/

Fundamentals of Transportation/About

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Fundamentals of Transportation/

About

This book is aimed at undergraduate civil engineering students, though the material may

provide a useful review for practitioners and graduate students in transportation. Typically, this would be for an Introduction to Transportation course, which might be taken by most students in their sophomore or junior year. Often this is the first engineering course students take, which requires a switch in thinking from simply solving given problems to formulating the problem mathematically before solving it, i.e. from straight-forward

calculation often found in undergraduate Calculus to vaguer word problems more reflective of the real world.

How an idea becomes a road

The plot of this textbook can be thought of as "How an idea becomes a road". The book begins with the generation of ideas. This is followed by the analysis of ideas, first

determining the origin and destination of a transportation facility (usually a road), then the required width of the facility to accommodate demand, and finally the design of the road in terms of curvature. As such the book is divided into three main parts: planning, operations, and design, which correspond to the three main sets of practitioners within the

transportation engineering community: transportation planners, traffic engineers, and

highway engineers. Other topics, such as pavement design, and bridge design, are beyond

the scope of this work. Similarly transit operations and railway engineering are also large topics beyond the scope of this book.

Each page is roughly the notes from one fifty-minute lecture.

Authors

Authors of this book include David Levinson [1], Henry Liu [2], William Garrison [3], Adam

Danczyk, Michael Corbett

References

[1] http://nexus.umn.edu

[2] http://www.ce.umn.edu/~liu/

[3] http://en.wikipedia.org/wiki/William_Garrison_(geographer)

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Fundamentals of Transportation/Introduction

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Fundamentals of Transportation/

Introduction

Transportation moves people

and goods from one place to

another using a variety of

vehicles across different

infrastructure systems. It does

this using not only technology

(namely vehicles, energy, and

infrastructure), but also

people’s time and effort;

producing not only the desired

outputs of passenger trips and

freight shipments, but also

adverse outcomes such as air

pollution, noise, congestion,

crashes, injuries, and

fatalities.

Figure 1 illustrates the inputs,

outputs, and outcomes of

transportation. In the upper

left are traditional inputs

(infrastructure (including

pavements, bridges, etc.),

Transportation inputs and outputs

labor required to produce

transportation, land consumed

by infrastructure, energy inputs, and vehicles). Infrastructure is the traditional preserve of civil engineering, while vehicles are anchored in mechanical engineering. Energy, to the extent it is powering existing vehicles is a mechanical engineering question, but the design of systems to reduce or minimize energy consumption require thinking beyond traditional

disciplinary boundaries.

On the top of the figure are Information, Operations, and Management, and Travelers’ Time and Effort. Transportation systems serve people, and are created by people, both the system owners and operators, who run, manage, and maintain the system and travelers who use it.

Travelers’ time depends both on freeflow time, which is a product of the infrastructure

design and on delay due to congestion, which is an interaction of system capacity and its use. On the upper right side of the figure are the adverse outcomes of transportation, in particular its negative externalities:

• by polluting, systems consume health and increase morbidity and mortality;

• by being dangerous, they consume safety and produce injuries and fatalities;

• by being loud they consume quiet and produce noise (decreasing quality of life and

property values); and

• by emitting carbon and other pollutants, they harm the environment.

Fundamentals of Transportation/Introduction

5

All of these factors are increasingly being recognized as costs of transportation, but the most notable are the environmental effects, particularly with concerns about global climate change. The bottom of the figure shows the outputs of transportation. Transportation is

central to economic activity and to people’s lives, it enables them to engage in work, attend school, shop for food and other goods, and participate in all of the activities that comprise human existence. More transportation, by increasing accessibility to more destinations,

enables people to better meet their personal objectives, but entails higher costs both

individually and socially. While the “transportation problem” is often posed in terms of congestion, that delay is but one cost of a system that has many costs and even more

benefits. Further, by changing accessibility, transportation gives shape to the development of land.

Modalism and Intermodalism

Transportation is often divided into infrastructure modes: e.g. highway, rail, water, pipeline and air. These can be further divided. Highways include different vehicle types: cars, buses, trucks, motorcycles, bicycles, and pedestrians. Transportation can be further separated into freight and passenger, and urban and inter-city. Passenger transportation is divided in

public (or mass) transit (bus, rail, commercial air) and private transportation (car, taxi, general aviation).

These modes of course intersect and interconnect. At-grade crossings of railroads and

highways, inter-modal transfer facilities (ports, airports, terminals, stations).

Different combinations of modes are often used on the same trip. I may walk to my car,

drive to a parking lot, walk to a shuttle bus, ride the shuttle bus to a stop near my building, and walk into the building where I take an elevator.

Transportation is usually considered to be between buildings (or from one address to

another), although many of the same concepts apply within buildings. The operations of an elevator and bus have a lot in common, as do a forklift in a warehouse and a crane at a port.

Motivation

Transportation engineering is usually taken by undergraduate Civil Engineering students.

Not all aim to become transportation professionals, though some do. Loosely, students in this course may consider themselves in one of two categories: Students who intend to

specialize in transportation (or are considering it), and students who don't. The remainder of civil engineering often divides into two groups: "Wet" and "Dry". Wets include those studying water resources, hydrology, and environmental engineering, Drys are those

involved in structures and geotechnical engineering.

Transportation students

Transportation students have an obvious motivation in the course above and beyond the

fact that it is required for graduation. Transportation Engineering is a pre-requisite to further study of Highway Design, Traffic Engineering, Transportation Policy and Planning, and Transportation Materials. It is our hope, that by the end of the semester, many of you will consider yourselves Transportation Students. However not all will.

Fundamentals of Transportation/Introduction

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"Wet Students"

I am studying Environmental Engineering or Water Resources, why should I care about

Transportation Engineering?

Transportation systems have major environmental impacts (air, land, water), both in their construction and utilization. By understanding how transportation systems are designed

and operate, those impacts can be measured, managed, and mitigated.

"Dry Students"

I am studying Structures or Geomechanics, why should I care about Transportation

Engineering?

Transportation systems are huge structures of themselves, with very specialized needs and constraints. Only by understanding the systems can the structures (bridges, footings,

pavements) be properly designed. Vehicle traffic is the dynamic structural load on these structures.

Citizens and Taxpayers

Everyone participates in society and uses transportation systems. Almost everyone

complains about transportation systems. In developed countries you seldom here similar

levels of complaints about water quality or bridges falling down. Why do transportation

systems engender such complaints, why do they fail on a daily basis? Are transportation

engineers just incompetent? Or is something more fundamental going on?

By understanding the systems as citizens, you can work toward their improvement. Or at

least you can entertain your friends at parties

Goal

It is often said that the goal of Transportation Engineering is "The Safe and Efficient Movement of People and Goods."

But that goal (safe and efficient movement of people and goods) doesn’t answer:

Who, What, When, Where, How, Why?

Overview

This wikibook is broken into 3 major units

Transportation Planning: Forecasting, determining needs and standards.

Traffic Engineering (Operations): Queueing, Traffic Flow Highway Capacity and Level of Service (LOS)

Highway Engineering (Design): Vehicle Performance/Human Factors, Geometric Design

Fundamentals of Transportation/Introduction

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Thought Questions

• What constraints keeps us from achieving the goal of transportation systems?

• What is the "Transportation Problem"?

Sample Problem

• Identify a transportation problem (local, regional, national, or global) and consider

solutions. Research the efficacy of various solutions. Write a one-page memo

documenting the problem and solutions, documenting your references.

Abbreviations

• LOS - Level of Service

• ITE - Institute of Transportation Engineers

• TRB - Transportation Research Board

• TLA - Three letter abbreviation

Key Terms

• Hierarchy of Roads

• Functional Classification

• Modes

• Vehicles

• Freight, Passenger

• Urban, Intercity

• Public, Private

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Transportation Economics/Introduction

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Transportation Economics/

Introduction

Transportation systems are subject to constraints and face questions of resource allocation.

The topics of supply and demand, as well as equilibrium and disequilibrium, arise and give shape to the use and capability of the system.

Demand Curve

How much would people pay for a final grade of an A in a transportation engineering class?

• How many people would pay $5000 for an A?

• How many people would pay $500 for an A?

• How many people would pay $50 for an A?

• How many people would pay $5 for an A?

If we draw out these numbers, with the price on the Y-axis, and the number of people

willing to pay on the X-axis, we trace out a demand curve. Unless you run into an

exceptionally ethical (or hypocritical) group, the lower the price, the more people are

willing to pay for an "A". We can of course replace an "A" with any other good or service, such as the price of gasoline and get a similar though not identical curve.

Demand and Budgets in Transportation

We often say "travel is a derived demand". There would be no travel but for the activities being undertaken at the trip ends. Travel is seldom consumed for its own sake, the

occasional "Sunday Drive" or walk in the park excepted. On the other hand, there seems to be some innate need for people to get out of the house, a 20-30 minute separation between the home and workplace is common, and 60 - 90 minutes of travel per day total is common, even for nonworkers. We do know that the more expensive something is, the less of it that will be consumed. E.g. if gas prices were doubled there will be less travel overall. Similarly, the longer it takes to get from A to B, the less likely it is that people will go from A to B.

In short, we are dealing with a downward sloping demand curve, where the curve itself

depends not only on the characteristics of the good in question, but also on its complements or substitutes.

The Shape of Demand

What we need to estimate is the shape of demand (is it

linear or curved, convex or concave, what function best

describes it), the sensitivity of demand for a particular

thing (a mode, an origin destination pair, a link, a time

of day) to price and time (elasticity) in the short run and

the long run.

Demand for Travel

• Are the choices continuous (the number of miles

driven) or discrete (car vs. bus)?

• Are we treating demand as an absolute or a probability?

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Transportation Economics/Introduction

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• Does the probability apply to individuals (disaggregate) or the population as a whole

(aggregate)?

• What is the trade-off between money and time?

• What are the effects on demand for a thing as a function of the time and money costs of competitive or complementary choices (cross elasticity).

Supply Curve

How much would a person need to pay you to write an A-quality 20 page term paper for a

given transportation class?

• How many would write it for $100,000?

• How many would write it for $10,000?

• How many would write it for $1,000?

• How many would write it for $100?

• How many would write it for $10?

If we draw out these numbers for all the potential entrepreneurial people available, we

trace out a supply curve. The lower the price, the fewer people are willing to supply the paper-writing service.

Equilibrium in a Negative Feedback System

Supply and Demand comprise the economists view of

transportation systems. They are equilibrium systems.

What does that mean?

It means the system is subject to a negative feedback

process:

An increase in A begets a decrease in B. An increase B

begets an increase in A.

Example: A: Traffic Congestion and B: Traffic Demand

... more congestion limits demand, but more demand

creates more congestion.

Negative feedback loop

Supply and Demand Equilibrium

As with earning grades and cheating, transportation is not free, it costs both time and

money. These costs are represented by a supply curve, which rises with the amount of

travel demanded. As described above, demand (e.g. the number of vehicles which want to

use the facility) depends on the price, the lower the price, the higher the demand. These two curves intersect at an equilibrium point. In the example figure, they intersect at a toll of $0.50 per km, and flow of 3000 vehicles per hour. Time is usually converted to money

(using a Value of Time), to simplify the analysis.

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Transportation Economics/Introduction

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Costs may be variable and include users' time,

out-of-pockets costs (paid on a per trip or per distance

basis) like tolls, gasolines, and fares, or fixed like

insurance or buying an automobile, which are only

borne once in a while and are largely independent of

the cost of an individual trip.

Disequilibrium

However, many elements of the transportation system

Illustration of equilibrium between

do not necessarily generate an equilibrium. Take the

supply and demand

case where an increase in A begets an increase in B. An

increase in B begets an increase in A. An example

where A an increase in Traffic Demand generates more Gas Tax Revenue ( B) more Gas Tax Revenue generates more Road Building, which in turn increases traffic demand. (This

example assumes the gas tax generates more demand from the resultant road building than

costs in sensitivity of demand to the price, i.e. the investment is worthwhile). This is dubbed a positive feedback system, and in some contexts a "Virtuous Circle", where the "virtue" is a value judgment that depends on your perspective.

Similarly, one might have a "Vicious Circle" where a decrease in A begets a decrease in B

and a decrease in B begets a decrease in A. A classic example of this is where ( A) is Transit Service and ( B) is Transit Demand. Again "vicious" is a value judgment. Less service results in fewer transit riders, fewer transit riders cannot make as a great a claim on

transportation resources, leading to more service cutbacks.

These systems of course interact: more road building may attract transit riders to cars, while those additional drivers pay gas taxes and generate more roads.

One might ask whether positive feedback systems

converge or diverge. The answer is "it depends on the

system", and in particular where or when in the system

you observe. There might be some point where no

matter how many additional roads you built, there

would be no more traffic demand, as everyone already

consumes as much travel as they want to. We have yet

to reach that point for roads, but on the other hand, we

have for lots of goods. If you live in most parts of the

United States, the price of water at your house

probably does not affect how much you drink, and a

lower price for tap water would not increase your rate

of ingestion. You might use substitutes if their prices

Positive feedback loop (virtuous circle)

were lower (or tap water were costlier), e.g. bottled

water. Price might affect other behaviors such as lawn

watering and car washing though.

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Transportation Economics/Introduction

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Provision

Transportation services are provided by both the public

and private sector.

• Roads are generally publicly owned in the United

States, though the same is not true of highways in

other countries. Furthermore, public ownership has

not always been the norm, many countries had a long

history of privately owned turnpikes, in the United

States private roads were known through the early

1900s.

• Railroads are generally private.

• Carriers (Airlines, Bus Companies, Truckers, Train

Positive feedback loop (vicious circle)

Operators) are often private firms

• Formerly private urban transit operators have been taken over by local government from the 1950s in a process called municipalization. With the rise of the automobile, transit systems were steadily losing passengers and money.

The situation is complicated by the idea of contracting or franchising. Often private firms operate "public transit" routes, either under a contract, for a fixed price, or an agreement where the private firm collects the revenue on the route (a franchise agreement).

Franchises may be subsidized if the route is a money-loser, or may require bidding if the route is profitable. Private provision of public transport is common in the United K