Jean-Paul Rodrigue (2013), New York:
Routledge, 416 pages.
Author: Dr. Jean-Paul Rodrigue
1. Challenges Facing Urban Transportation
Cities are locations having a high level of accumulation and
concentration of economic activities and are complex spatial
structures that are supported by transport systems. The larger the
city, the greater its complexity and the potential for disruptions,
particularly when this complexity is not effectively managed. The most important
transport problems are often related to urban areas and take place when
transport systems, for a variety of reasons, cannot satisfy the numerous
requirements of urban mobility. Urban productivity is highly dependent
on the efficiency of its transport system to move labor, consumers and
freight between multiple origins and destinations. Additionally, important
transport terminals such as ports, airports, and railyards are located
within urban areas, contributing to a specific array of problems. Some
problems are ancient, like congestion (which plagued cities such as
Rome), while others are new like urban freight distribution or environmental
impacts. Among the most notable urban transport problems are:
Many dimensions to the urban transport challenge are linked with
the dominance of the automobile.
Automobile use is obviously related to a variety of advantages such
as on demand mobility, comfort, status, speed, and convenience. These
advantages jointly illustrate why
continues to grow worldwide, especially in urban areas. When given
the choice and the opportunity, most individuals will prefer using an
automobile. Several factors influence the growth of the total vehicle
fleet, such as sustained economic growth (increase in income and quality
of life), complex individual urban movement patterns (many
households have more than one automobile), more leisure time and
suburbanization. Therefore, rising automobile mobility can be perceived
as a positive consequence of economic development. The acute growth
in the total number of vehicles also gives rise to congestion at peak
traffic hours on major thoroughfares, in business districts and often
throughout the metropolitan area.
Cities are important generators and attractors of movements, which
have created a set of geographical
paradoxes that are self-reinforcing. For instance, specialization
leads to additional transport demands while agglomeration leads to congestion.
Over time, a state of automobile dependency has emerged which results
in a diminution in the role of other modes, thereby limiting still further
alternatives to urban mobility. In addition to the
factors contributing to the growth of
driving, two major factors contributing to automobile dependency
- Traffic congestion and parking difficulties. Congestion
is one of the most prevalent transport problems in large urban agglomerations,
usually above a threshold of
about 1 million inhabitants.
It is particularly linked with motorization and the diffusion of
the automobile, which has increased the demand for transport infrastructures.
However, the supply of infrastructures has often not been able to
keep up with the growth of mobility. Since vehicles spend the majority
of the time parked, motorization has expanded the
demand for parking
space, which has created space consumption problems particularly
in central areas; the spatial
imprint of parked vehicles is significant. Congestion and
parking are also interrelated since looking for a parking space
(called "cruising") creates additional delays and impairs local circulation.
In central areas of large cities cruising may account for more
than 10% of the local circulation as drivers can spend 20
minutes looking for a parking spot. This practice is often
judged more economically effective than using a paying
off-street parking facility as the time spent looking for a
free (or low cost) parking space as compensated by the monetary savings. Also, many
delivery vehicles will simply double-park at the closest
possible spot to unload their cargo.
- Longer commuting. On par with congestion
people are spending an increasing amount of time
commuting between their
residence and workplace. An important factor behind this trend
is related to residential affordability as housing located
further away from central areas (where most of the employment
remains) is more affordable. Therefore, commuters are trading
time for housing affordability. However, long commuting is
linked with several social problems, such as isolation, as well
as poorer health (obesity).
- Public transport inadequacy. Many public transit systems,
or parts of them, are either over or under used. During peak hours,
crowdedness creates discomfort for users as the system copes with
a temporary surge in demand. Low ridership makes many services financially
unsustainable, particularly in suburban areas. In spite of significant
subsidies and cross-financing (e.g. tolls) almost every public transit
systems cannot generate sufficient income to cover its operating
and capital costs. While in the past deficits were deemed
acceptable because of the essential service public transit was
providing for urban mobility, its financial burden is
- Difficulties for non-motorized transport. These difficulties are
either the outcome of intense traffic, where the mobility of pedestrians,
and vehicles is impaired, but also because of a blatant lack of
consideration for pedestrians and bicycles in the physical design of
infrastructures and facilities.
- Loss of public space. The majority of roads are publicly
owned and free of access. Increased traffic has adverse impacts
on public activities which once crowded the streets such as markets,
agoras, parades and processions, games, and community interactions.
These have gradually disappeared to be replaced by automobiles.
In many cases, these activities have shifted to shopping malls while
in other cases, they have been abandoned altogether. Traffic flows
influence the life and interactions of residents and their usage
of street space. More traffic impedes social interactions and street
activities. People tend to walk and cycle less when traffic is high.
- Environmental impacts and energy consumption. Pollution,
including noise, generated by circulation has become a serious impediment
to the quality of life and even the health of urban populations.
Further, energy consumption by urban transportation has dramatically
increased and so the dependency on petroleum. Yet, peak oil
considerations are increasingly linked with peak mobility
expectations where high energy prices incite a shift towards
more efficient and sustainable forms of urban transportation,
namely public transit.
- Accidents and safety. Growing traffic in urban areas
is linked with a growing number of accidents and fatalities, especially
in developing countries. Accidents account for a significant share
of recurring delays. As traffic increases, people feel less safe
to use the streets.
- Land consumption. The territorial imprint of transportation
is significant, particularly for the
automobile. Between 30 and 60% of a metropolitan area may be
devoted to transportation, an outcome of the over-reliance on some
forms of urban transportation. Yet, this land consumption also underlines
the strategic importance of transportation in the economic and social
welfare of cities.
- Freight distribution. Globalization and the materialization
of the economy have resulted in growing quantities of freight moving
within cities. As freight traffic commonly shares infrastructures
with the circulation of passengers, the mobility of freight in urban
areas has become increasingly
strategies can be established to mitigate the variety of challenges
faced by urban freight distribution.
There are several levels
of automobile dependency, ranging from low to acute, with their
corresponding land use patterns and alternatives to mobility. Among
the most relevant indicators of
automobile dependency are the level of vehicle ownership, per capita
motor vehicle mileage and the proportion of total commuting trips made
using an automobile. A situation of high automobile dependency is reached
when more than three quarters of commuting trips are done using the
automobile. For the United States,
this proportion has remained around 88% over the recent decades. Automobile
dependency is also served by a cultural and commercial system promoting
the automobile as a symbol of status and personal freedom, namely through
intense advertising and enticements to purchase new automobiles. Not
surprisingly, many developing countries perceive motorization as a condition
for development. Even if the term automobile dependency is often negatively
perceived and favored by market distortions such as the provision of
roads, its outcome reflects the choice of individuals who see the automobile
more as an advantage then an inconvenience.
The second half of the 20th century saw the adaptation of many cities
in North America and Europe to automobile circulation. Motorized transportation
was seen as a powerful symbol of modernity and development. Highways
were constructed, streets were enlarged, and parking lots were set often
disrupting the existing urban fabric with the creation of motorized
cities. However, from the 1980s, motorization started to be seen more
negatively and several cities implemented policies to limit automobile
circulation, at least in specific areas, by a set of strategies including:
- Underpricing and consumer choices. Most road infrastructures
are subsidized as they are considered a public service. Consequently,
drivers do not bear the full cost of automobile use. Like the "Tragedy
of the Commons", when a resource is free of access (road), it tends
to be overused and abused (congestion). This is also reflected in
consumer choice, where automobile ownership is a symbol of status,
freedom and prestige, especially in developing countries. Single
home ownership also reinforces automobile dependency.
- Planning and investment practices. Planning and the ensuing
allocation of public funds aim towards improving road and parking
facilities in an ongoing attempt to avoid congestion. Other transportation
alternatives tend to be disregarded. In many cases, zoning regulations
impose minimum standards of road and parking services and de facto
impose a regulated automobile dependency.
Tentative solutions have been put forth such as transport planning
measures (synchronized traffic lights, regulated parking), limited vehicle
traffic in selected areas, the promotion of bicycle paths and public
transit. In Mexico City, vehicle use is prohibited according to license
plate numbers and the date (even-uneven). Affluent families have solved
this issue by purchasing a second vehicle, thus worsening the existing
situation. Singapore is the only country in the world which has successfully
controlled the amount and growth rate of its vehicle fleet by imposing
a heavy tax burden and purchasing permits on automobile owners. Such
a command-based approach is unlikely to be possible in other contexts.
There is a growing body of evidence underlining that a
peak level of car mobility is unfolding, at least in
developed countries. Higher energy prices, congestion and the
general aging of the population are all countervailing forces to car
dependency. For instance, since 2006 the amount of vehicle-miles
traveled in the United States has
process associated with higher energy prices and a strong recession. There are many alternatives to automobile dependency such as intermodality
(combining the advantages of individual and collective transport),
carpooling (strengthened by policy and regulation by the US government)
or non-motorized transportation (walking and cycling).
These alternatives can only be partially implemented as the
automobile remains on the short and medium terms the prime choice
for providing urban mobility.
- Dissuasion. Although automobile circulation is permitted,
it is impeded by regulations and physical planning. For instance,
parking space can be severely limited and speed bumps placed to
force speed reduction.
- Prohibition of downtown circulation. During most of the
day the downtown area is closed to automobile circulation but deliveries
are permitted during the night. Such strategies are often undertaken
to protect the character and the physical infrastructures of an
historical city. They do however, like most policies, have unintended
consequences. If mobility is restrained in certain locations or
during certain time periods, people will simply go elsewhere (longer
movements) or defer their mobility for another time (more movements).
- Tolls. Imposing tolls for parking and entry (congestion
pricing) to some parts of the city has been a strategy being considered
seriously in many area as it confers the potential advantage of
congestion mitigation and revenue generation. Most evidence underlines
however that drivers are willing to bear additional toll costs
for the convenience of using a car,
especially for commuting since it is linked with their
main source of income.
Congestion occurs when transport demand exceeds transport supply
at a specific point in time and
in a specific section of the transport system. Under such circumstances,
each vehicle impairs the mobility of others.
Congestion can be perceived as an unavoidable consequence of the
usage of scarce transport resources, particularly if they are not priced.
The last decades have seen the extension of roads in rural but particularly
in urban areas, most of them free of access. Those infrastructures were
designed for speed and high capacity, but the growth of urban circulation
occurred at a rate higher than often expected. Investments came from
diverse levels of government with a view to provide accessibility to
cities and regions. There were strong incentives for the expansion of
road transportation by providing high levels of transport supply. This
has created a vicious circle of congestion
which supports the construction of additional road capacity and automobile
dependency. Urban congestion mainly concerns two domains of circulation,
often sharing the same infrastructures:
It is important to underline that congestion in urban areas is dominantly
caused by commuting patterns and little by truck movements. On average,
infrastructure provision was not able to keep up with the growth in
the number of vehicles, even more with the total number of vehicles-km.
During infrastructure improvement and construction, capacity impairment
(fewer available lanes, closed sections, etc.) favors congestion. Important
travel delays occur when the
capacity limit is reached or exceeded, which is the case of almost
all metropolitan areas. In the largest cities such as London, road
traffic is actually slower than it was 100 years ago. Marginal
delays are thus increasing and driving speed becomes problematic as
the level of population density
increases. Once a population threshold
of about 1 million is reached, cities start to experience recurring
congestion problems. This observation must be nuanced by
numerous factors related to the urban setting, modal preferences and
the quality of existing urban transport infrastructures. Still, large cities
have become congested most of the day, and
congestion is getting more acute.
Another important consideration concerns parking, which consumes large
amounts of space and provides limited economic benefit. In automobile
dependent cities, this can be very constraining as each economic activity
has to provide an amount of parking space proportional to their level
of activity. Parking has become a land use
that greatly inflates the demand for urban land.
Urban mobility also reveals congestion patterns. Daily trips can
be either “mandatory” (workplace-home) or “voluntary” (shopping, leisure,
visits). The former is often performed within fixed schedules while
the latter complies with variable and discretionary schedules. Correspondingly,
congestion comes in two major forms:
- Passengers. In many regions of the world incomes have
significantly increased to the point that one automobile per household
or more is common. Access to an automobile conveys flexibility in
terms of the choice of origin, destination and travel time. The
automobile is favored at the expense of other modes for most trips,
including commuting. For instance, automobiles account for the
bulk of commuting trips in the
- Freight. Several industries have shifted their transport
needs to trucking, thereby increasing the usage of road infrastructure.
Since cities are the main destinations for freight flows (either
for consumption or for transfer to other locations) trucking adds
to further congestion in urban areas. The "last mile" problem remains
particularly prevalent for freight distribution in urban areas.
Congestion is commonly linked with a drop in the frequency of deliveries
tying additional capacity to insure a similar level of service.
Behavioral and response time effects are also important as in a system
running close to capacity, simply breaking suddenly may trigger what
can be known as a backward traveling wave. It implies that as
vehicles are forced to stop, the bottleneck moves up the location it
initially took place at, often leaving drivers puzzled about its cause.
The spatial convergence of traffic causes a surcharge on transport infrastructures
up to the point where congestion can lead to the total immobilization
of traffic. Not only does the massive use of the automobile have an
impact on traffic circulation and congestion, but it also leads to the
decline in public transit efficiency when both are sharing the
In some areas, the automobile is the only mode for which infrastructures
are provided. This implies less capacity for using alternative modes
such transit, walking and cycling. At some levels of density, no public
infrastructure investment can be justified in terms of economic returns.
Longer commuting trips in terms of
average travel time, the result of fragmented land uses and congestion
levels are a significant trend. Convergence of traffic at major highways
that serve vast low density areas with high levels of automobile ownership
and low levels of automobile occupancy. The result is energy (fuel)
wasted during congestion (additional time) and supplementary commuting
distances. In automobile dependent cities, a few measures can help alleviate
congestion to some extent:
- Recurrent congestion. The consequence of factors that
cause regular demand surges on the transportation system, such as
commuting, shopping or weekend trips. However, even recurrent congestion
can have unforeseen impacts in terms of its duration and severity.
Mandatory trips are mainly responsible for the peaks in circulation
flows, implying that about half the congestion in urban areas is
recurring at specific times
of the day and on specific segments of the transport system.
- Non-recurrent congestion. The other half of congestion
is caused by random events such as accidents and unusual
weather conditions (rain, snowstorms, etc.), which are unexpected
and unplanned. Non-recurrent congestion is linked to the presence
and effectiveness of incident response strategies. As far as accidents
are concerned, their randomness is influenced by the level of traffic
as the higher the traffic on specific road segments the higher the
probability of accidents.
All these measures only partially address the issue of congestion,
as they alleviate, but do not solve the problem. Fundamentally, congestion
remains a failure at reconciling mobility demands and acute supply constraints.
5. The Urban Transit Challenge
As cities continue to become more dispersed, the cost of building
and operating public transportation systems increases. For instance,
as of 2012 only about 184 urban agglomerations have a
subway system, the great
majority of them being in developed countries. Furthermore, dispersed
residential patterns characteristic of
automobile dependent cities makes
public transportation systems less convenient to support urban mobility.
In many cities additional investments in public transit did not result
in significant additional ridership. Unplanned and uncoordinated land
development has led to rapid expansion of the urban periphery. Residents,
by selecting housing in outlying areas, restrict their potential access
to public transportation. Over-investment (when investments do not appear
to imply significant benefits) and under-investment (when there is a
substantial unmet demand) in public transit are both complex challenges.
Urban transit is often perceived as the most efficient transportation
mode for urban areas, notably large cities.
However, surveys reveal a stagnation of public transit
systems, especially in North America.
The economic relevance of public transit is being questioned. Most urban
transit developments had little, if any impacts to alleviate congestion
in spite of mounting costs and heavy subsidies. This paradox
is partially explained by the spatial structure of contemporary cities
which are oriented along servicing the needs of the individual, not
necessarily the needs of the collectivity. Thus, the automobile remains
the preferred mode of urban transportation. In addition, public transit
is publicly owned, implying that it is a politically motivated service
that provides limited economic returns. Even in transit-oriented
cities such as in Europe, transit systems
depend massively on government subsidies. Little or no competition
is permitted as wages and fares are regulated, undermining any price
adjustments to changes in ridership. Thus, public transit often serves
the purpose of a social function (“public service”) as it provides accessibility
and social equity, but with limited relationships with economic activities.
Among the most difficult challenges
facing urban transit are:
- Ramp metering. Controlling the access to a congested
highway by letting automobiles in one at a time instead of in groups.
The outcome is a lower disruption on highway traffic flows.
- Traffic signal synchronization. Tuning the traffic signals
to the time and direction of traffic flows. This is particularly
effective if the signals can be adjusted on an hourly basis to reflect
changes in commuting patterns.
- Incident management. Making sure that vehicles involved
in accidents or mechanical failures are removed as quickly as possible
from the road. Since accident on average account between 20 and
30% of all the causes of congestion, this strategy is
- Carpooling. Concerns two issues. The first
and most common is an individual providing ridership to people (often
co-workers) having a similar origin, destination and commuting time.
Two or more vehicle trips can thus be combined into one. The second
involves a pool of vehicles (mostly cars, but also
bicycles) that can be leased
for short durations when mobility is required. Adequate measures
must be taken so that supply and demand are effectively matched.
- HOV lanes. High Occupancy Vehicle (HOV) lanes insure
that vehicles with 2 or more passengers (buses, vans, carpool, etc.)
have exclusive access to a less congested lane, particularly during
- Congestion pricing. A variety of measures aimed at imposing
charges on specific segments or regions of the transport system,
mainly as a toll. The charges can also change during the day to
reflect congestion levels so that drivers are incited to consider
other time periods or other modes.
- Parking management. Removing parking or
free parking spaces can be an effective dissuasion tool since it
reduces cruising and enables those willing to pay to access an
area (e.g. for a short shopping stop).
- Public transit. Offering alternatives to driving that
can significantly improve efficiency, notably if it circulates on
its own infrastructure (subway, light rail, buses on reserved lanes,
etc.) and is well integrated within a city's development plans.
However, public transit has its own set of issues (see next
- Non-motorized transportation. Since the
great majority of urban trips are over short distances,
non-motorized modes, particularly walking and cycling, have an
important roll to play in supporting urban mobility. The
provision of adequate infrastructure, such as sidewalks, is
often a low priority as non-motorized transportation is often
perceived as not modern in spite of the important role it needs
to assume in urban areas.
There are indications that public transit is reassessing its role
in societies with high levels of automobile dependency. The rise in
petroleum prices since 2006 has increased the cost of vehicle
ownership and operation. A younger generation is perceiving the
automobile as a less attractive proposition than the prior
generation and is more willing to use public transit and live in
higher density areas. Electronic fare systems are also making the
utilization of public transit more convenient. A recent trend
concerns the usage of incentives, such as point systems (e.g. air
miles with purchase of a monthly pass) to further promote the use of
public transit and to influence consumer behavior.
- Decentralization. Public transit systems are not designed
to service low density and scattered urban areas that are increasingly
dominating the landscape. The greater the decentralization of urban
activities, the more difficult and expensive it becomes to serve
urban areas with public transit. Additionally, decentralization
promotes long distance trips on transit systems causing higher operating
costs and revenue issues for flat fare transit systems.
- Fixity. The infrastructures of several public transit
systems, notably rail and subway systems are fixed, while cities
are dynamical entities, even if the pace of change can take decades.
This implies that travel patterns tend to change and that a transit
system built for servicing a specific pattern may eventually face
- Connectivity. Public transit systems are often independent
from other modes and terminals. It is consequently difficult to
transfer passengers from one system to the other. This leads to a
paradox between the preference of riders to have direct connections
and the need to provide a cost efficient service network that involves
- Competition. In view of cheap and ubiquitous road transport
systems, public transit faced strong competition and loss ridership
in relative terms and in some cases in absolute terms. The higher
the level of automobile dependency, the more inappropriate the public
transit level of service. The public service being offered is simply
outpaced by the convenience of the automobile. However, changes
in energy prices are likely to impose a new equilibrium in this
- Financing and fare structures. Most public transit systems
have abandoned a distance-based fare structure to a simpler flat fare system. This
had the unintended consequence of discouraging short trips for which
most transit systems are well suited for, and encouraging longer
trips that tend to be more costly per user than the fares they generate.
Information systems offer the possibility for transit systems to
move back to a more equitable distance based fare structure.
- Legacy costs. Most public transit systems employ
unionized labor that have consistently used strikes (or the threat
of a strike) and the acute disruptions they create as leverage to
negotiate favorable contracts, including health and retirement benefits.
Since public transit is subsidized these costs were not well reflected
in the fare systems. In many transit systems, additional
subsidies went into compensation or to cover past debt, and not
necessarily into performance improvements or additional
infrastructure. As most governments are facing stringent budgetary
constraints because of unsustainable social welfare commitments,
public transit agencies are being forced to reassess their budgets
through an unpopular mix of higher fares, deferred maintenance and
the breaking of labor contracts. The era of public transit as a
welfare agency providing compensation and benefits well above the
qualifications and the productivity of its labor may be drawing
to an end.