Tài liệu Urban Transportation Systems: Choices for Communicaties pptx

1CHAPTER

Overview—Criteria

for Selecting Modes

Life in cities—i.e., in organized human settlements, which are

mostly referred to as communities in this book—is possible only if

people have mobility1 on a daily basis—the ability to move around

so that they can do what they have to do or like to do. One characterization of a city is that it consists of specialized, frequently

clustered, activities that perform discrete functions. Residences

are separate from workplaces, major shopping is concentrated in

identifiable centers, and larger entertainment and relaxation facilities are found at specific locations. They have to have accessibility.2 Unlike in a village, very few of these destinations are

reachable on foot; at least, they tend not to be within a convenient

walking distance.

The large ancient and medieval cities were actually conglomerations of neighborhoods in which daily life could take place

1 Mobility is here defined as the ability of any person to move between points in

a community by private or public means of transportation. The usual obstacles

to mobility are long distances, bad weather, steep hills (all constituting friction

of space), but, above all, the unavailability of services, high fares, and possibly

other forms of exclusion.

2 Accessibility is here defined as the possibility of reaching any activity, establishment, or land use in a community by people (or by conveyances of goods or

information) who have a reason to get there. It is a measure of the quality and

operational effectiveness of a community.

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Source: Urban Transportation Systems

2 Urban Transportation Systems

within a short radius; only occasionally was a longer trip to a

major event necessary. Industrialization during the nineteenth

century caused a true urban revolution by disaggregating the

small-scale pattern into metropolitan structures with strong and

intensive production and service zones. Assisted transportation

became mandatory, and was, indeed, quickly invented—horse

cars, steam railroads, electric streetcars, and eventually underground metro (electric heavy rail) systems.

The twentieth century brought further development of the rail

modes, and introduced individual motor (gasoline- and dieselpowered) vehicles—buses and automobiles. The latter came to

dominate the transportation field, at least in North America, and

dispersed the urban pattern further into sprawl. We are all familiar with this situation, since this is our environment, and it has

been examined endlessly by scholars, journalists, and concerned

citizens. What is not quite so apparent is that urban life and spatial patterns are entering a new, postindustrial, period, which is

characterized by the emergence of many dispersed specialpurpose centers (not just the historic single all-purpose center),

overall low densities, and movement in many different directions

at any given time with diverse trip purposes. Electronic communications systems play an increasingly large role. All this makes it

more difficult to operate effectively the traditional transportation

modes that served us well under more structured conditions.

Everything has not changed, but the task of providing responsive

transportation services is now more challenging. Also, the expectations are higher.

There is a large inventory of available means of mobility today,

most of them tested under various conditions in various places. In

the United States, it is not just a question of how to cope with the

automobile—admittedly a very seductive mode—but rather of

how to equip our communities with a reasonable array of transportation choices, so that the best aggregate level of mobility is

offered to all people. Never before has any other culture enjoyed

the same freedom of movement, but there are deficiencies: not

everybody can take full advantage of the current car-based transportation capabilities, and the systems that we do have are not

necessarily (quite unlikely, in fact) the best, the most economical,

the cleanest, and the most responsive options that could be provided. The vehicular pollution problem is perhaps on the verge of

being solved, if some serious additional effort is applied, but

plenty of other issues remain.

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Overview—Criteria for Selecting Modes

Overview—Criteria for Selecting Modes 3

The trends and problems are global, and while the scope of

inquiry of this book is definitely directed to North America, these

concerns do not exist in isolation, certainly not as far as transportation technology is concerned. It is common practice to refer to

“industrialized countries” as having special needs and capabilities—which is an obsolete concept, because industry (i.e., manufacturing) is no longer the determining factor. The search for a

proper label has some significance. “Advanced countries” is a

pompous and patronizing characterization that does not contribute

much to an operational discussion. “Peer countries” has some

validity, but only if everything is compared to a U.S. situation.

“Developing countries,” on the other hand, is a very common term

that helps to summarize broad descriptions, but obscures the fact

that there is tremendous variety among these countries. Saudi Arabia, Brazil, Kenya, and Indonesia do not fit in the same box easily.

The fact of the matter is that cities and their populations are

not homogeneous in different parts of the world, not even within

the same country (not even in Sweden). Each city has components

that range in their transportation expectations from the most

comfortable to the most affordable. There are districts in African

cities that expect and can pay for the most advanced services, and

there are neighborhoods in American metropolitan areas that are

not much different from those found in Third World countries.

The relative size of the various user cohorts is, of course, different, but the demands within them are quite similar.

Therefore, for the purposes of examining transportation needs,

it can be suggested that we recognize the presence of various economic and social classes (user groups) that react differently to

transportation systems and have to be serviced differently. In a

perfect world, such distinctions would not have to be made, since

everybody is entitled to mobility. Equity is an important concept,

and social reforms are undoubtedly needed in many instances,

but the duty of urban transportation is to provide service for communities the way we find them today. Purposeful and relevant

change comes next, but upgraded mobility systems can only do so

much in implementing community reforms.

Thus, to define a base for the discussion of transportation

modes, the following distinctions that are present in any society

can be made:

• The affluent elite. This group is basically separate and only

barely visible from the outside. The members live and play

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Overview—Criteria for Selecting Modes

4 Urban Transportation Systems

in their own enclaves and have their own means of mobility

(limousines and private jets). They do not affect the rest of

us, except to cause some envy; they do not participate in

daily urban operations, and they do not use the subway.

They do have much influence in decision making.

• The prosperous cohort. This group has the same expectations from transportation services as everybody else—rapid,

comfortable, and secure accommodations—but members of

this group can exercise a choice and be selective. They insist

on control over their private space, and they might use public transportation, but only if it meets very high standards.

The expense of transportation is not a significant barrier;

the demand is for individually responsive means of unconstrained mobility. The private automobile does this (most of

the time), and there is an open question as to what proportion of Americans falls in this group of dedicated motorists

who have no other choices in mind.

• The middle class. This group has largely the same attitudes

as the previous group, except that they operate with more

frugal means. They include among their members proportionally more individuals who will favor public transportation as a matter of principle and the proper thing to do. It

has always been the case that the professional and educated

classes lead the public debate, start revolutions, and

demand reforms. They have to be counted on as the formulators of public opinion, and they will determine policy

directions in places where they constitute a vocal presence.

It is a fact that members of this group, whether they are

Argentines, Egyptians, Belgians, or Americans, will act and

behave in the same way and demand the same type of services and facilities. They all read the same books and drive

the same cars. The only differences among them are their

relative proportion of the populace in any given society and

some cultural variations. Europeans, for example, cherish

their old city districts; Americans regard them as quaint

“theme” areas; and members of emerging societies are still

frequently embarrassed by them.

• The surviving cohort. This group consists of working people of modest means whose principal preoccupation is basic

existence. They have little influence on decisions and politiDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)

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Overview—Criteria for Selecting Modes

Overview—Criteria for Selecting Modes 5

cal processes—except in instances where they constitute the

overwhelming majority and are politically organized. They

need and deserve transportation services, but they cannot

afford high charges, and their choices tend to be limited.

Some degree of subsidy will almost always be necessary to

attain acceptable service levels.

• The disadvantaged class. This group includes the poor and

those who have some personal handicap and insufficient

resources to purchase proper services. Poverty always comes

at different levels, but the problems are universal and unforgiving. This group represents the largest challenge to public

agencies and institutions in achieving basic mobility for all.

No social assistance program really works unless physical

accessibility is ensured. Communities in the United States

are certainly not immune from these requirements, and the

current “welfare-to-work” effort is only one example of the

initiatives needed.

The preceding is not by any means intended to be a sociological analysis of contemporary societies, but only a hypothesis of

how different populations react to mobility needs and services

provided. More specifically, the adequacy of operations can be

looked at from three perspectives, which eventually leads to the

selection of a proper response or transportation mode:

• The point of view of the individual, which will stress personal attitudes and emphasize usually humanly selfish considerations

• The policy of the community, which has to stress the common good and long-range capabilities

• The concerns related to national efficiency and well-being

The personal concerns will encompass the following:

• Time spent in travel. This includes time spent to reach the

vehicle or access point, to possibly wait, to actually travel,

to possibly transfer, and to reach the final destination (probably on foot).

• Costs incurred. These include primarily the out-of-pocket

expenses on any given trip (including possible tolls and purchase of fuel), but there are also considerations of previous

investment (buying a car) and the sunk costs (investment in

equipment and insurance).

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Overview—Criteria for Selecting Modes

6 Urban Transportation Systems

• Operational quality. This concerns reliability, safety (from

accidents), and smoothness of motion.

• Human amenities. These include security (from criminal

activity), privacy, sanitation, climate control, seats, visual

quality, and social standing.

The communal concerns should include the following:

• Efficient networks and services. They should have the ability to support economic and social life, and cause minimal

disruptions and delays in normal urban operations.

• Efficient urban patterns. To the extent that transportation

systems can help to achieve more compact settlement forms,

the configurations and activity locations should be deliberately shaped.

• High degree of livability. Transportation modes should provide access to all places and establishments and have minimal local environmental and visual impacts.

• Economic strength. Economic development, tax revenues,

and local jobs should be boosted due to good transportation.

• Fiscal affordability. Services should result in limited drain

on local resources, maximum use of external assistance,

minimal indebtedness, and low annual contributions.

• Institutional peace. There should be minimal need to

change ordinances or regulations, modify labor rules, displace families and establishments, disturb existing institutions, etc.

• Civic image and political approval. Services should include

features that are admired by outsiders and endorsed by local

residents (voters) and businesses.

The national concerns exist at a higher and overarching level,

and they might not always be achieved if left to local initiatives:

• Use of national wealth. This involves the implementation

and operation of the most cost-effective systems, particularly as seen from the perspective of the national budget.

• Conservation of fuel resources. This particularly concerns

those derived from petroleum.

• Environmental quality. Air quality over large areas and

regions demands specific attention.

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Overview—Criteria for Selecting Modes

Overview—Criteria for Selecting Modes 7

• Equity. This is a concern to ensure that the needs of the

less-privileged members of society are specifically addressed.

• National technological capability. Those systems that enhance technological advancement and production capacity

within the country should be emphasized.

• Well-functioning, well-equipped, and balanced communities.

Such built environments should be created in all parts of the

country and within all metropolitan areas.

Recognizing the fact that no proposed or existing transportation system can satisfy equally well three separate sets of criteria,

there is a need to amalgamate the preceding lists, perhaps even to

make some compromises. There is also the practical consideration

that the discussion here has to move toward workable guidelines

for the selection of appropriate modes in any given urban setting.

This means that some of the considerations are so overarching

and basic that they simply have to be accepted as given; others

make no distinction among modes and, therefore, are not operative in the evaluation process. Attention has to turn to functional

aspects. All services and systems eventually exist and perform at

the local level in communities.

Trip Purpose and Clientele

Most transportation modes can make a reasonable claim to be

able to satisfy all trip purposes within a community. They have

to, because no city can provide too many overlapping services.

There are, however, modes that respond best to selected situations with identifiable needs. These usually encompass paratransit and various high-technology modes (shuttles and district

services). With respect to user groups, the options are more complicated, because people tend to have differing expectations.

These range from placing comfort features first to a single-minded

emphasis on affordability. Concerns with equity very much enter

into these evaluations.

Geographic Coverage and Grain of Access

The more capital-intensive modes best serve concentrated corridors, and door-to-door accessibility has to be added by feeder services. The grain of the former has to be rather coarse, i.e., not able

to reach many dispersed points directly. Any mode that attempts

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Overview—Criteria for Selecting Modes

8 Urban Transportation Systems

to do the latter as communal transit for the sake of user convenience will not be in a position to provide rapid service, because

of the many stops that will have to be made. To a large extent, this

consideration explains the popularity of the private automobile.

Carrying Capacity

Transportation modes available today cover a wide spectrum in

their ability to do work, i.e., carry people. A fundamental and

not-too-difficult selection task is choosing a proper mode to

respond to estimated demand volumes. If the users from a district

number a dozen or so during a day, only individual street-based

vehicles (perhaps in joint use) can be considered; if they number

several tens of thousands, a subway will have to be built. The

suitable responses at the extreme ends of the scale will be expensive in one way or another.

Speed

Time distances, not physical distances, are of concern here. For

any given traveler in an urban situation, the maximum speed that

a vehicle or train can attain on an open channel is of little interest; what matters is the total time consumed from the origin point

to the destination and the inconveniences of transfers along the

way. The private automobile is a formidable competitor again,

except on truly congested street networks. The aggregate rapidity

of movement is also a communal concern to the extent that time

spent in travel is unproductive and tiresome to the participants.

Passenger Environment

In a prosperous society, personal comfort and convenience features are increasingly significant. If certain levels in quality of life

have been attained in residences and workplaces, greatly inferior

conditions will not be tolerated during travel. These features

encompass the smoothness of the ride, privacy (or at least some

distance from strangers), sanitation, climate control, availability

of seats, visual quality, and anything else that registers through

human senses. The challenging task in communal transit is to

measure up to what private cars provide.

Reliability

Life in contemporary cities is stressful enough, and our society (as

well as our employer) expects punctuality. Delays in traffic and

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Overview—Criteria for Selecting Modes

Overview—Criteria for Selecting Modes 9

travel are acceptable only as rare occurrences. There are modes

that are more immune to traffic overloads and bad weather (railbased, mostly), and there are others that are quite vulnerable to

urban disruptions (street-based, mostly).

Safety and Security

Residents in cities are well sensitized, through continuous media

attention, toward issues of personal safety and security—for good

reasons. This is mostly a matter of the overall level of civilized

behavior in a community and police protection, but there are

modes that are perceived to be more susceptible to antisocial

action and physical breakdown than others.

Conservation of the Natural Environment and Fuel

The attention paid lately to the quality of air and water around us

and the concerns with resource depletion enter in the planning

and design of many urban systems, particularly so with transportation. While these are national issues with national mandates, solutions can be achieved only through work at the local

level, even if the consequences of any individual small action may

be seen as marginal. Generally speaking, transit is benign, and

low-occupancy automobile use is damaging.

Achievement of a Superior Built Environment

We can continue to expect that major transportation systems that

significantly enhance the accessibility of specific nodes or corridors will generate a positive effect on land use and distribution of

activities. This feature has potential for organizing the urban pattern, but evidence shows that this does not happen in all

instances and it does not happen automatically—unless other

constructive organizing programs are also implemented.

Costs

The expenses associated with transportation improvements and

management can be broken down in considerable detail, but the

commonly listed elements are right-of-way acquisition, construction of the channel (roadway or guideway) and facilities, purchase

of rolling stock, and annual operation and maintenance expenses,

which include compensation for the work force, purchase of fuel

or power and supplies, maintenance of equipment and facilities,

and managerial expenditures. Nothing is cheap, but some modes

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Overview—Criteria for Selecting Modes

10 Urban Transportation Systems

involve massive capital investments, while others consume large

amounts of resources to run services and maintain hardware. It

should not matter in the long run whether the funds come from

municipal, state, or federal budgets since they are all drawn from

the wealth of the entire society and country, but it does matter

when decisions have to be made with respect to any specific system. The costs, either in their entirety or by separate components,

are frequently, as might be expected, the life-or-death factors for

any transportation project.

Implementability

This concern refers to elements that are complex, not always well

defined, and frequently obscure to the general public in the political and institutional realms, sometimes reflecting established

practices and habits. They can be critical items if progress with

any project is expected, and they may sometimes represent insurmountable barriers. The engineers have an equivalent term—

buildability—in public works construction. But that is a comparatively easy task since it refers to the physical ability to get

something done. Implementability encompasses social, administrative, and political arrangements and habits, often unique to a

specific community. Transportation systems affect much more

than tangible artifacts and their operation. These factors operate

at the local and state levels primarily, and no generalizations will

be made here, except to call for serious attention and understanding well before any irreparable damage is done due to

neglect or ignorance.

Image

Transportation systems and services are the public face of a community. Everybody comes in contact with them, and they are usually the first thing that a visitor from the outside experiences.

They are elements of civic pride in many instances, and they

show the seriousness that is applied to the creation of a livable

and efficient community. But pride can also be a sin, and there

are instances on record in which transportation solutions have

been implemented for reasons other than functional necessity.

This should not happen with full knowledge of the capabilities

and potential of transportation modes in the contemporary city.

There are legitimate reasons to applaud service systems that

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Overview—Criteria for Selecting Modes

Overview—Criteria for Selecting Modes 11

respond to the needs and capabilities of a community, to take

pride in something that works well.

We should be ready now to apply the preceding criteria as a

screen in reviewing the many transportation modes available for

service. We shape our service systems, they do not shape us, but

they do have a fundamental role in defining the structure of communities and how we live and operate in cities and metropolitan

areas. Transportation systems and land use are two sides of the

same coin. To achieve the exact built environment that we wish to

have, work with both of them in a mutually supporting fashion is

indicated. The record from the past has not always been inspired;

we have the means, the methods, the choices, and, let us hope,

the knowledge today to do better.

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Overview—Criteria for Selecting Modes

12 Urban Transportation Systems

CAMBRIDGE, Mass.—

Many people who are willing to concede that the

railroad must be brought

back to life are chiefly

thinking of bringing this

about on the very terms

that have robbed us of a

balanced transportation

network—that is, by treating speed as the only

important factor, forgetting reliability, comfort

and safety, and seeking

some mechanical dodge for

increasing the speed and

automation of surface

vehicles.

My desk is littered with

such technocratic fantasies,

hopefully offered as “solutions.” They range from

old-fashioned monorails

and jet-propelled hovercraft

(now extinct) to a more scientific mode of propulsion

at 2,000 miles an hour,

from completely automated

highway travel in private

cars to automated vehicles

a Government department

is now toying with for

“facilitating” urban traffic.

What is the function of

transportation? What

place does lomocotion [sic]

occupy in the whole spectrum of human needs?

Perhaps the first step in

developing an adequate

transportation policy

would be to clear our

minds of technocratic

cant. Those who believe

that transportation is the

chief end of life should be

put in orbit at a safe lunar

distance from the earth.

The prime purpose of

passenger transportation is

not to increase the amount

of physical movement but

to increase the possibilities

for human association,

cooperation, personal

intercourse, and choice.

A balanced transportation system, accordingly,

calls for a balance of

resources and facilities

and opportunities in every

other part of the economy.

Neither speed nor mass

demand offers a criterion

of social efficiency. Hence

such limited technocratic

proposals as that for highspeed trains between

already overcrowded and

overextended urban centers would only add to the

present lack of functional

balance and purposeful

organization viewed in

terms of human need.

Variety of choices, facilities and destinations, not

speed alone, is the mark of

an organic transportation

system. And, incidentally,

this is an important factor

of safety when any part of

the system breaks down.

Even confirmed air travelers appreciate the railroad

in foul weather.

If we took human needs

seriously in recasting the

whole transportation system, we should begin with

the human body and make

the fullest use of pedestrian movement, not only

for health but for efficiency in moving large

crowds over short distances. The current introduction of shopping malls,

free from wheeled traffic,

is both a far simpler and

far better technical solution than the many costly

proposals for introducing

moving sidewalks or other

rigidly automated modes

of locomotion. At every

stage we should provide

for the right type of locomotion, at the right speed,

within the right radius, to

meet human needs. Neither maximum speed nor

maximum traffic nor maximum distance has by itself

any human significance.

With the overexploitation of the motor

car comes an increased

demand for engineering

equipment, to roll ever

wider carpets of concrete

over the bulldozed landscape and to endow the

petroleum magnates of

Texas, Venezuela and Arabia with fabulous capacities for personal luxury

and political corruption.

Finally, the purpose of

this system, abetted by

similar concentration on

planes and rockets, is to

keep an increasing volume of motorists and

tourists in motion, at the

highest possible speed, in

a sufficiently comatose

state not to mind the fact

that their distant destination has become the exact

counterpart of the very

place they have left. The

end product everywhere

is environmental desolation.

If this is the best our

technological civilization

can do to satisfy genuine

human needs and nurture

man’s further development, it’s plainly time to

close up shop. If indeed

we go farther and faster

along this route, there is

plenty of evidence to

show that the shop will

close up without our

help. Behind our power

blackouts, our polluted

environments, our transportation breakdowns, our

nuclear threats, is a failure of mind. Technocratic

anesthesia has put us to

sleep. Results that were

predictable—and predicted!—half a century

ago without awakening

any response still find us

unready to cope with

them—or even to admit

their existence.

Transportation: “A Failure of Mind”

Lewis Mumford

estate of Lewis Mumford.)

Thirty years ago, Lewis Mumford articulated his vision as to what urban transportation should be. It

is valid today, although it still remains a vision.

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Overview—Criteria for Selecting Modes

2CHAPTER

Walking

Background

We are all pedestrians; any trip by any means includes at least a

small distance covered on foot at the beginning and end of each

journey. Walking is the basic urban transportation mode that has

allowed settlements and cities to operate for thousands of years.

It is still very much with us, but its role has been eroded with the

introduction of mechanical means of transportation, drastically so

in American communities, with the dominant presence of the private automobile in the last half century.

The principal transportation mode in the developing world,

even in large cities, is still walking because of constraints on the

resources needed to operate extensive transit systems. People

cover long distances on foot every day and expend human energy

that they can scarcely spare. Walking under those conditions is an

unavoidable chore that consumes productive capability. In North

America and Western Europe, the attitude and policies are just

the opposite: walking is efficient, healthful, and natural. We

should do more of it—almost everybody agrees—and some of the

current trends should be reversed. Ironically, among the most

popular exercise machines in health clubs and in homes are treadmills that simulate walking, which could be otherwise accomplished with a transport purpose on the street.

Source: Urban Transportation Systems

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14 Urban Transportation Systems

Admittedly, because of the size of contemporary metropolitan

areas, with origin and destination points far apart, the need to

save time consumed in routine travel, and the desire for basic

comfort and avoidance of severe weather conditions, walking as

a transportation mode has limitations. But the niche that it can

fill is still rather large, and the opportunities are by no means

fully exploited. Just the reverse is happening today, and some

proactive programs will be necessary to restore reasonable balance.

The trend in the percentage of commuters who walk to work in

the United States1 has been negative:

1960 9.9 percent

1970 7.4 percent

1980 5.6 percent

1990 3.9 percent

19992 3.1 percent

Much of this can be explained by the fact that land use patterns have become more coarse-grained (i.e., greater segregation

of job places and commercial activities from residences), and

trips have become longer overall, but there is also the greater

propensity to use the car for any purpose, even just to go around

the corner. Working at home has increased slightly, but not

enough by far to explain the drop in walking to and from workplaces. Appeals to reason and civic responsibility will not alter

the prevailing attitudes much; programs to make walking attractive to individuals will have to be expanded and implemented.

The contemporary built environment in North America is not

always fully enabling toward pedestrians. Not all new streets

have sidewalks, they are not always structured into coherent networks, and they frequently lack proper amenities (good pavement, lighting, rest areas, etc.).

1 U.S. Census data.

2 Since the 2000 U.S. Census data were not yet available, information from the

American Household Survey was used for 1999.

Walking

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