Author: Dr. Jean-Paul Rodrigue
Urban mobility is organized into three broad categories of collective, individual, and freight transportation. While the mobility of passengers is the outcome of individual decisions based on different rationales, freight mobility is decided in tandem between the cargo owners and transportation service providers.
1. Urban Mobility and its Evolution
Urban areas are the most complex settings in which the mobility of passengers and freight is taking place. In several instances, passengers and freight movements are complementary, but sometimes they may be competing for the usage of available land and transport infrastructures:
- Collective Transportation (public transit). The purpose of collective transportation is to provide publicly accessible mobility over specific parts of a city. The systems are usually owned and operated by an agency, and access is open to all as long as a fare is paid; the reason why they are called public transit. The efficiency of public transit systems is based upon transporting large numbers of people and achieving economies of scale. It includes modes such as tramways, buses, trains, subways, and ferries.
- Individual Transportation. Includes any mode where mobility is the outcome of a personal choice and means such as the automobile, walking, cycling, or the motorcycle. Most people walk to satisfy their basic mobility, but this number varies according to the city being considered. Some forms of individual mobility could be favored, while others could be impaired. For instance, walking accounts for 88% of all movements within Tokyo’s central area, while this figure is only 3% for Los Angeles. The density and design of the former are more accommodating to the individual mobility of pedestrians than the latter.
- Freight Transportation. Since cities are dominant centers of production and consumption, urban activities are accompanied by large movements of freight. These movements are mostly characterized by delivery trucks moving between industries, distribution centers, warehouses, and retail activities as well as from major terminals such as ports, railyards, distribution centers, and airports. The growth of e-commerce has been associated with an increase in the home deliveries of parcels. The mobility of freight within cities tends to be overlooked but is part of an emerging field related to city logistics.
Rapid urban development occurring across much of the globe increased the mobility of passengers and freight within urban areas. Mobility also tends to involve longer distances, but evidence suggests that commuting times have remained relatively similar over the last hundred years; approximately 1 to 1.2 hours per day is spent on average commuting. This means that commuting has gradually shifted to faster transport modes, and consequently, greater distances could be traveled using the same amount of time.
Each form of urban mobility, be it walking, the automobile, or urban transit, has a level of suitability to fill mobility needs. Different transport technologies and infrastructures have been implemented, resulting in a wide variety of urban transport systems around the world. In developed economies, there have been four general eras of urban development, each associated with a different form of urban mobility, with a fifth phase unfolding.
a. The Walking-Horsecar Era (1800s – 1890s)
Even during the industrial revolution, the dominant mean of getting around was on foot. Walking cities were typically less than 5 kilometers in diameter, making it possible to walk from the downtown to the city edge in about 30 minutes. Land use was mixed, and density was high (e.g. 100 to 200 people per hectare). The city was compact, and its shape was more-or-less concentric. Still, the industrial revolution brought additional populations through rural to urban migrations, improved construction techniques allowing for higher densities and new forms and locations of employment. The development of the first public transit in the form of omnibus service extended the diameter of the city but did not change the overall urban structure.
The railroad facilitated the first real change in the urban morphology. New developments, often referred to as trackside suburbs, emerged as small nodes that were physically separated from the city itself and one another. The nodes coincided with the location of rail stations and stretched out a considerable distance from the city center, usually up to a half-hour train ride. Within the city proper, rail lines were also laid down, and horse-cars introduced mass transit.
b. The Electric Streetcar or Transit Era (1890s – 1920s)
The invention of the electric traction motor created a revolution in urban travel. The first electric trolley line opened the late 19th century and was quickly adopted in a large number of cities. The operating speed of electric trolley was three times faster than that of horse-drawn vehicles and did not generate wastes. The streetcar city was able to spread outward 20 to 30 kilometers along the streetcar lines, creating an irregular, star-shaped pattern. The urban fringes became areas of rapid residential development. Trolley corridors became commercial strips that would come to characterize the main commercial areas. The city core was further entrenched as a mixed-use, high-density zone. Land use patterns reflected social stratification where outer suburban areas were typically middle class, while the working class continued to concentrate around the central city.
As street congestion increased in the first half of the 20th century due to the diffusion of the automobile, the efficiency of streetcar systems deteriorated as cars infringed their right of way. Further, many cities had ordinances that prevented fare increases, implying that many streetcar systems became unprofitable, leading to a lack of maintenance and investment in additional services. These factors contributed to the demise of many streetcar systems in the later part of the 20th century.
c. The Automobile Era (1930s – 1950s)
The automobile was introduced in European and North American cities in the 1890s, but only the wealthy could afford this innovation. From the 1920s, ownership rates increased dramatically, with lower prices made possible by assembly-line production techniques. As automobiles became more common, land development patterns changed. Developers were attracted to green-field areas located between the suburban rail corridors, and the public was attracted to these single-use zones, thus avoiding many inconveniences associated with the city, mainly pollution, crowding, and lack of space. Still, this phase usually represented the peak share of public transit in urban mobility as suburban developments did not yet account for a large share of the urban landscape, and cities were still high density and transit-dependent.
d. The Freeway Era (1950s – 2010s)
In the second half of the 20th century, the massive diffusion of the automobile, as well as the construction of highway networks, had substantial impacts on urban mobility. Highways were built to connect the central business district to outlying areas and, in many cases, complete or partial ring roads were built. The personal mobility offered by the automobile represented a paradigm shift in terms of lifestyle, consumption patterns, as well as residential locations. The automobile reduced the friction of distance considerably, which led to urban sprawl. The emergence of the suburb created a new landscape in which public transit did not fit well with few services being offered to these new residential areas. Transit ridership fell, and transit companies ran into financial difficulties. Eventually, transit services throughout North America and Europe became subsidized, publicly-owned enterprises. Some tramway systems were being dismantled, and the surviving transit lines were those that were separated from road circulation, namely subway systems.
New light rail systems were introduced, but they could generate ridership if large parking lots were provided at suburban stations. Commercial activities also began to suburbanize as well, creating additional passenger and freight mobility systems. Within a short period, the automobile became the dominant mode of travel in all cities of North America and from the 1970s in a growing number of developed and developing economies. Since the 2000s, a similar process took place in China on a massive scale. Wherever incomes rise, the growth of automobile use tends to increase accordingly. Motorization and the diffusion of personal mobility have been an ongoing trend linked with substantial declines in the share of public transit in urban mobility.
e. The Integrated Mobility Era (2010s onward)
Throughout their evolution, urban transportation modes remained rather disconnected, particularly since they are owned and operated by separate entities such as transit agencies, automobile owners, or trucking companies that did not interact much. The diffusion of information and communication technologies is changing this relationship. Emerging urban mobility systems are gaining from a higher level of integration, resulting in better levels of asset utilization. An early example concerns on-demand vehicle services pooling individual drivers and matching their mobility supply with the consumer demand through a platform accessible through a mobile device. In several high-density markets, the outcome of this convenience was a surge in demand for for-hire vehicles. A further development concerns self-driving vehicles that could expand mobility options and a better utilization level of automobile assets. This era is also associated with the diffusion of e-commerce and its associated home deliveries, underlining the issue of city logistics and last-mile freight distribution. On the more conventional market of food deliveries, information technologies have also allowed pooling resources, replacing business-specific deliveries with fleets of on-demand vehicles.
In many areas of the world where urbanization is more recent, the above synthetic phases did not take place. Fast urban growth led to a scramble to provide transport infrastructure inadequately, leading to rather chaotic conditions supporting urban mobility.
2. A Taxonomy of Urban Mobilities
Mobility is linked to specific urban activities and land use, with each type involving the generation and attraction of an array of movements. This relationship is complex but is linked to factors such as recurrence, income, urban form, density, level of development, and technology. Urban mobility is either obligatory when it is linked to scheduled activities (such as home-to-work trips), or voluntary when those generating it are free to decide of their scheduling (such as leisure). The most common types of urban mobility types are:
- Pendulum movements. These are obligatory movements involving commuting between locations of residence and work. They are highly cyclical since they are predictable and recurring regularly, most of the time a daily occurrence, thus the term pendulum.
- Professional movements. These are movements linked to professional, work-based activities such as meetings, repair, maintenance, and customer services, dominantly taking place during work hours.
- Personal movements. These are voluntary movements linked to the location of commercial activities, which includes shopping and recreation.
- Touristic movements. Important for cities having historical and recreational features. They involve interactions between landmarks and amenities such as hotels and restaurants and tend to be seasonal or occurring at specific moments. Major sports events such as the World Cup or the Olympics are important generators of urban movements during their occurrence.
- Distribution movements. These are concerned with the distribution of freight to satisfy consumption and manufacturing requirements. They are mostly linked to transport terminals, distribution centers, and retail outlets. However, the growth of online transactions involves more freight movements being carried to residential areas; home deliveries.
The consideration of urban mobility, both for passengers and freight, involves their generation, the modes and routes used, and their destination:
- Trip generation. On average, an urban resident undertakes between 3 and 4 trips per day. Moving in an urban area is usually done to satisfy a purpose such as employment, leisure, or access to goods and services. The activity space of an individual is an important trip generation factor since it indicates the travel that needs to be undertaken. Temporal variations in the number of trips by purpose are observed with commuting as the most prevalent pattern. Similar temporal variations are observed for the mobility of freight, with the majority of this mobility taking place in the morning when goods are delivered to retail outlets. This often leads to conflicts with the mobility of passengers since vehicles are sharing the same road infrastructure, including parking space, which in urban areas is the object of capacity constraints.
- Modal split. This implies the use of a series of transportation modes for urban trips, which is the outcome of a modal choice. This choice depends on several factors, such as cost, technology, availability, preference, travel time (distance), and income. Therefore, walking, cycling, public transit, the automobile, or even telecommuting, are going to be used either as a choice or as a constraint (lack of choice). For instance, locations within five minutes of walking are considered to be readily accessible to pedestrians. Urban freight distribution can also use a variety of modes, but the van and the truck tend to dominate.
- Trip assignment (routing). Involves which routes will be used for trips within the city. Passenger trips usually have a stable routing. For instance, a commuter driving a car has, most of the time, a fixed route between his/her residence and place of work. This route may be modified if there is congestion or if another activity (such as shopping) is linked with that trip, a practice often known as trip chaining. The routing of freight distribution is dependent on the types of deliveries involved. For large retail outlets, direct deliveries are the norm, while for smaller stores and parcel deliveries, vehicles will accommodate flexible routing. Several factors influence trip assignment, the most important being transport costs, time, and congestion levels.
- Trip destination. Changes in the spatial distribution of economic activities in urban areas have caused important modifications to trip destination, notably those related to work. Activity-based considerations are essential since each economic activity tends to be associated with a level of trip attraction. Retail, public administration, entertainment, and restoration are the activities that attract the most movements per person employed. For freight movements, manufacturing, transport terminals, and retail are the activities attracting the most movements. The central city used to be a major destination for trips, particularly passengers, but its share has substantially declined in most areas, and suburbs now account for the bulk of urban trips.
Mobility is also a social issue. The share of the automobile in urban trips varies in relation to location, social status, income, quality of public transit, and parking availability. Mass transit is often affordable, but several social groups, such as students, the elderly, and the poor, are a captive market. There are important variations in mobility according to age, income, gender, and disability, with policies aiming at promoting the accessibility and mobility of groups perceived as disadvantaged. The gender gap in mobility is the outcome of socio-economic differences as access to individual transportation is dominantly a matter of income. Within households, differences in role and income are related to the respective activity range and mobility of its members. Consequently, in some instances, modal choice is more a modal constraint linked to economic opportunities.
Central locations generally have the most urban mobility options because private, and public transport facilities are present. However, this does not mean that mobility is easier since central areas are congested. In locations outside the central core, a share of the population not having access to the automobile is facing a level of isolation or at least a more limited access to amenities and employment opportunities. Limited public transit and high automobile ownership costs have created a group of spatially constrained (mobility deprived) people.
3. Urban Transit
Transit is almost exclusively an urban transportation mode, particularly in large urban agglomerations. The urban environment is particularly suitable for transit because it provides conditions fundamental to its efficiency, namely high density and significant short distance mobility demands. Since transit is a shared service, it potentially benefits from economies of agglomeration related to high densities and from economies of scale related to high mobility demands. One key advantage of public transit is the higher the demand, the more effective public transit services can be offered. Lower densities are linked with lower demand and a greater likelihood of public transit systems operating at a loss and requiring subsidies. In fact, most public transit systems are not financially sound and have to be subsidized, even if several of their core segments are profitable. Transit systems are made up of many types of services, each suitable to a specific set of market and spatial context. Different modes are used to provide complementary services within the transit system and in some cases between the transit system and other transport systems.
- Bus transit. One of the most common forms of urban transit that includes vehicles of various sizes (from small vans to articulated buses) offering seating and standing capacity along scheduled routes and services. They usually share roadways with other modes and are therefore susceptible to congestion. Bus rapid transit systems offer a permanent or temporary right of ways and have the advantage of unencumbered circulation.
- Rail transit. Vehicles of fixed guideways that usually have their own right of way. Light rail systems are composed of streetcars that can share the right of ways, particularly in central areas. Heavy rail systems are commonly called subways or metro since many operate underground. Another type of rail transit concerns commuter rail systems that are usually servicing central business districts and peripheral areas along specific corridors.
- Taxi systems. Usually private for-hire vehicles such as automobiles, jitneys or rickshaws to offer point to point services. Recent technological developments have enabled car-sharing services and expanded the availability of on-demand transit.
- Alternative transit. Refer to transit systems that were developed to cope with specific conditions (or niche markets) using alternative modes. Ferries are the most common form of alternative transit as they are servicing cities having waterways separating different urban districts. Funiculars are also prevalent in locations that have a steep incline and enough traffic to justify their construction. Aerial lifts are also used in some settings to connect locations difficult of access.
Contemporary transit systems tend to be publicly owned, implying that many decisions related to their development and operation are politically motivated. This is a sharp contrast of what took place in the past, as most transit systems were private and profit-driven initiatives. With the fast diffusion of the automobile in the 1950s, many transit companies faced financial difficulties, and the quality of their service declined; in a declining market, there were limited incentives to invest. Gradually, they were purchased by public interests and incorporated into large agencies, mainly to continue providing mobility. As such, public transit often serves more a social function of public service and a tool of social equity than having an economic role. Transit has become dependent on government subsidies, with little if any competition permitted as wages and fares are regulated. As a result, they tend to be disconnected from market forces, and subsidies are required to keep a level of service. With suburbanization, transit systems tend to have even fewer relationships with economic activities.
Government-owned public transit systems are facing financial difficulties for three main reasons. The first is that they are often designed to service taxpayers, not necessarily potential customers. Because of the funding base, transit systems may be spread into neighborhoods that do not provide a significant customer base. The second is that transit unions were able to extract substantial advantages in terms of wages and social benefits, increasing labor costs. The third concerns a technology fixation which incites to invest in high-cost transit (e.g. light rail transit) while low-cost solutions (buses) would have been sufficient to many transit systems, particularly in lower-density areas.
Reliance on urban transit as a mode of urban transportation tends to be high in Asia, intermediate in Europe and low in North America. Since their inception in the early 19th century, comprehensive urban transit systems had significant impacts on the urban form and spatial structure, but this influence is receding. Three major classes of cities can be found in terms of the relationships they have with their transit systems:
- Adaptive cities. Represent transit-oriented cities where urban form and urban land use developments are coordinated with transit developments. While central areas are adequately serviced by a metro system and are pedestrian-friendly, peripheral areas are oriented along transit rail lines.
- Adaptive transit. Represent cities where transit plays a marginal and residual role and where the automobile accounts for the dominant share of movements. The urban form is decentralized and of low density.
- Hybrids. Represent cities that have sought a balance between transit development and automobile dependency. While central areas have an adequate level of service, peripheral areas are automobile-oriented.
Contemporary land development tends to precede the introduction of urban transit services, as opposed to concomitant developments in earlier phases of urban growth. Thus, new services are established once the demand is deemed to be sufficient, often after being the subject of public pressures. Transit authorities operate under a service warrant and are usually running a recurring deficit as services are becoming more expensive to provide. This has led to a set of considerations aimed at a higher integration of transit in the urban planning process, particularly in cities where such a tradition is not well established.
From a transportation perspective, the potential benefits of better integration between transit and local land uses are reduced trip frequency and increased use of alternative modes of travel (i.e. walking, biking, and transit). Evidence is often lacking to support such expectations since the relative share of public transit ridership is declining across the board. There is usually a reciprocal relationship between automobile ownership and the use of public transit. Good accessibility to public transit is often associated with lower automobile use while areas of high automobile use may impair the development of public transit systems since the automobile is already dominant.
Community and land use design can consequently have a significant influence on travel patterns. Local land use impacts can be categorized into three dimensions of relationships in terms of accessibility, the convergence of mobility and land use integration they provide. Land use initiatives are trying to be coordinated with other planning and policy initiatives to cope with automobile dependence. However, there is a strong bias against transit in the general population because of negative perceptions, especially in North America, but increasingly globally. As personal mobility is a symbol of status and economic success, the users of public transit are perceived as the least successful segment of the population. This bias may undermine the image of transit use within the general population but can be subject to change with the evolution of social norms and values.
- Transportation and the Urban Form
- Urban Land Use and Transportation
- Urban Transport Challenges
- City Logistics
- Information Technologies and Mobility
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