Transportation Engineering

Summary

Transportation engineering is an area of specialty within the field of civil engineering. Transportation engineers are concerned with the design and building of large-scale systems that move people from one place to another. These systems include roads, railway and subway networks, and airports. The greatest demand for transportation engineers comes from cities, where the concentration of people living together is highest and where traffic is most likely to occur. The field of transportation engineering is growing due to a rise in urban populations during the twenty-first century. Increased awareness of fuel costs and environmental-impact issues are also driving the growth of transportation systems in cities.

Definition and Basic Principles

Transportation engineering is the design, development, and building of systems that move large numbers of people from one place to another. The need for systems like these is greatest in cities. Transportation engineers work closely with urban planners and engineers to make sure that the systems they design are a good fit with a city's overall needs, geography, and budget. Other stakeholders in transportation systems are local businesses, state and federal government agencies, and environmental groups. Transportation engineers also take into account the requirements of these stakeholders when a new system is planned.

Transportation systems can be categorized into modes defined by the type of infrastructure needed to run them. Buses, for example, need a fleet of vehicles and a network of roads and streets. Systems that need rails include trains, subways, light rail and monorail (considered separate categories from standard train systems such as commuter rail), and streetcars and trams. Ferries are used in many cities with extensive waterfront areas. Airports also fall within the domain of transportation engineering. While most transportation systems are designed with the needs of a geographically focused population in mind, airports are unique in that they serve passengers from all over the country—or the world.

Background and History

Before the nineteenth century, transportation engineering was limited. Problems with traffic on city roads had existed since the days of ancient Rome, but there were few mechanical alternatives to traveling by individual carriage, on horseback, or on foot.

The first public transportation systems are believed to be networks of stagecoaches that took paying passengers from a designated point within a city to one of several destinations outside of it. These networks appeared in major cities such as Paris, London, and New York at the beginning of the 1800s. They were followed by horse-drawn omnibuses that ran regularly on routes within city limits. By the 1860s, the first elevated trains were being designed and launched in American cities. Engines ran on steam at first but were quickly replaced by electric systems by the 1880s. Electric railways made it possible to shift track systems from elevated lines to underground tunnels. A boom in the building of subway systems followed in the United States and Europe with the turn of the century.

Public-transportation ridership peaked in the United States in 1944 and 1945. Rapid advancements in automobile technology, combined with the passage of the Federal Aid Highway Act in 1956, led to a decline in use of mass transit. Streetcar systems in many major US cities ceased in the mid-1950s. Sharp increases in gasoline prices in the 1970s briefly renewed interest in public transportation. The US Census Bureau found that only about three percent of Americans used public transportation to travel to work in 2022. However, that number increased to more than 33 percent in large cities like New York and San Francisco.

How It Works

Transportation engineers are involved at every stage of the process in developing and building transit systems. Some projects are large and may take many years, such as the construction of a new subway line. Others are as small as changes in an individual bus route. All transportation engineering projects go through a similar set of steps from start to finish.

Identification of Transit Needs. Before a new transit system can be designed, transportation engineers must clearly understand the needs of the passengers it will serve. Questions asked at this stage are: How many passengers will use the system each day? How will these patterns vary on weekdays versus weekends? When during the day will usage be highest (also known as peak time), and how much will this vary from off-peak times? Transit engineers also consider issues such as the choice of transportation mode, such as light rail versus bus, and the ways in which ridership would be affected. To answer these questions, transportation engineers work with urban planners and other professionals to gather information. The information comes from sources such as population maps, road traffic data, and surveys of residents living and working in the targeted areas.

Identification of Project Limits. All transit projects need resources to be built. Transit engineers must consider the budgets of city, state, and federal authorities in planning new systems. Funding from the private sector, such as large corporations or associations of businesses in an area, is used often, especially when companies are likely to benefit from the new system. Geography is another major factor in planning. The mode of transportation chosen and the budget needed to build the system depends heavily on the amount and type of land (or, in some cases, water) being covered. The environmental impact of a new transit system must also be studied. While public transportation is nearly always better for the environment on the whole than the same number of passengers driving individual cars, different modes of transportation affect the environment in different ways.

Model Creation and System Design. Once information has been gathered and the questions above have been answered, transportation engineers begin to create models of potential transit solutions, including the mode or modes to be used. These models are based on mathematical and engineering principles. They show the ways in which a new transit system would provide benefits for the costs involved. The models also track factors such as the geographic area covered, the density of the network (the number of routes and the distance passengers would need to travel to reach each one), the frequency and scheduling of routes, and the prices of fares. Transportation engineers must build models that show how the proposed system will meet both the current and the future needs of a community.

System Selection. Transportation engineers present their models and solutions to the stakeholders in a new transit system. These stakeholders include community residents, government agencies such as city councils and budget committees, and environmental groups. Once stakeholders have provided feedback, engineers incorporate their input into a revised version of the plan and seek final approval. In most cases, multiple meetings and rounds of feedback are needed before approval is granted by all stakeholders.

System Implementation. The approved transit system is ready to be brought into action. If the system is a small-scale change, such as a shift in bus routes, transportation engineers may set a specific period of time during which the change is tested. The engineers will establish goals and gather data during the test period to make sure the change is effective. If new equipment or infrastructure is needed, engineers will seek bids from manufacturers to get the highest-quality products for a competitive price. Vendors are selected, orders are placed, and the system is built.

Followup. Once the new system is in place, transportation engineers ensure that it runs properly and receives the ongoing maintenance and supplies it needs.

Applications and Products

Transportation engineers hold jobs that range from the preserving of historic railroads to the designing of new technologies. One of the easiest ways to understand the field of transportation engineering is to look at it by infrastructure type.

Highways, Roads, and Streets. The design and building of roads and the vehicles that use them are some of the largest fields employing transportation engineers. Roads must meet the needs of the greatest number of drivers and passengers with minimal traffic delays. They must follow federal, state, and local requirements governing the safety of their design and the quality of their construction materials. Roads must provide enough capacity for the needs of businesses while ensuring quality of life for consumers, especially in terms of traffic, noise, and pollution. Transportation engineers find ways to combine networks of highways, roads, and streets in order to gain the greatest benefit overall.

Bus systems are the primary form of mass transit found on roads. Buses reduce the amount of traffic and pollution generated by road travel as well as the cumulative wear and tear of tires on road surfaces. An advantage of bus systems is that they can be used in areas with lower population density, such as suburbs or small towns, for a smaller budget than would be needed to build a train or subway. Bus routes and frequency can also be changed easily, either in response to short-term demands such as construction or long-term shifts such as neighborhood growth. A disadvantage of bus transit is that, unless buses use dedicated lanes, bus routes can be subject to the same traffic problems faced by cars.

Heavy Rail. Transportation networks known as “heavy rail” include subway systems, commuter or regional rail lines, and intercity train systems such as Amtrak in the United States. In densely populated areas, particularly in the stretch of major cities known as the Northeast corridor (ranging approximately from Boston to Washington, DC), there is a great deal of overlap between heavy rail networks. It is often easy for passengers to transfer from one type of rail network to another simply by crossing a train platform.

Subways, also known as metros or rapid transit systems in some urban areas, are networks of trains that serve the needs of one city. Subway tracks often run through underground tunnels or on rails that are separated physically from passengers, pedestrians, and motor and bicycle traffic. This design allows many subway networks to use a third rail, charged with electricity, for power—a design that would not be possible or safe otherwise. Subways may also use rails elevated above the roadway or at grade (or ground) level. A subway system is distinguished from other types of heavy rail in that its trains often run more frequently, serve stations that are located closer together, and can sometimes (though not always) be ridden by passengers for a flat fare rather than a price determined by distance. However, not all subway systems worldwide follow this approach to fares. The London Underground, also known as the “tube,” because of the cylindrical shape of many of its trains and tunnels, is a subway system that prices fares in part based on distance traveled.

At the other end of the spectrum of heavy rail networks are interurban, or inter-city, train systems. These systems connect large cities to each other via a network that can cover an entire country or continent. In some countries, these networks are managed by a governmental agency or operated by a legally permitted and closely regulated monopoly. In other countries, a network of regional rail authorities works together to maintain the track networks and train schedules. Interurban trains have the lowest frequency in terms of the number of trains per day. They also serve a small number of train stations within a metropolitan area, often one or a few stations located in a central or downtown area. Fare pricing is based on distance and route traveled, though passes for unlimited travel by distance within a given time period—such as a month or a year—are often available.

Commuter rail can be seen as a hybrid between subway systems and interurban train systems. Like subways, commuter rail systems serve the needs of a single city or metropolitan area. Commuter trains use a network of tracks that provide service between a city's downtown and its suburbs. Stations are designed to serve the needs of passengers traveling a longer distance, so stops are spaced farther apart than on a subway line. Fares for individual rides are priced by distance traveled, but most passengers rely on commuter rail to travel regularly between work and home and are more likely to buy monthly or yearly passes.

Light Rail, Streetcars, and Trams. In contrast to heavy rail, many light rail and tram systems operate on a network specifically designed for the carrying of a limited number of passengers. Light rail trains often run on rails separated from roadways, while streetcars share space and right-of-way on streets with motor vehicles. Trams may or may not share space on roads in the way that streetcars do, depending on the city and system. This category generally does not use an electrified third rail for power. Instead, trains are more likely to be powered by a network of overhead wires to which each train maintains a direct connection. Diesel engines are also used to power trams. These systems usually require less capital to build and maintain than heavy rail.

Ferries and Water Taxis. Ferries, or ferryboats, are the primary form of mass transportation across bodies of water. Cities next to harbors, rivers, or coastal waters often establish ferry services as an integrated part of their mass transit systems. The Staten Island Ferry in New York City and the Star Ferry service in Hong Kong are two examples of ferries of this type. These ferries essentially serve as shuttles between two points, one on either side of a harbor or river. Water taxis, also called water buses, are used in cities with canals, such as Venice and Amsterdam, and follow routes with multiple stops. Other ferries, such as the commercially operated services between islands in Greece or Slovenia, carry passengers for longer trips and are closer in function to interurban trains.

Airports. Airports fall into a unique category in transportation engineering. Airports are managed by a local authority, often within the government agency that also oversees other forms of transportation infrastructure, such as shipping ports. Airports do not need a physical network of rails or roads to connect them to each other. However, they serve the needs of commercial and government-run airline and cargo services using a communications network that manages air traffic control. The design, building, and maintenance of airports is a highly specialized field of engineering with close ties to aerospace.

Careers and Course Work

Most transportation engineers hold a bachelor's or graduate degree. As a field, transportation engineering is too highly specialized to warrant its own major, so many students pursue majors such as civil engineering. Degrees in areas such as mechanical engineering, urban planning, geography, and probability and statistics would also have a number of applications within transportation engineering, though some additional courses dealing with transit systems might be needed.

Students begin with course work providing a general foundation in the principles of engineering. These courses would include physics, mathematics, materials science, general engineering, engineering technology, and design. Courses in civil engineering would examine the systems and structures needed to support large numbers of people, such as buildings, water systems, roads, railway networks, and bridges.

Opportunities to specialize further in transportation engineering vary by school. The ITE has compiled a list of college-level courses taught in the United States, Canada, and Australia on topics within transportation engineering. This list provides insight into the types of advanced education available. The list of courses also indicates which colleges and universities offer the widest range of course work options. The courses cover topics such as the design of traffic systems, intelligent systems and transportation, transit system modeling, and environmental issues in transportation design. The ITE also offers extensive continuing-education opportunities to professionals, including a Transportation Leadership Graduate Certificate.

Demand for new hires in the field of transportation engineering rises and falls with the availability of funding, especially from government agencies, for transit projects. However, technological developments and a changing awareness of the importance of environmental issues gives an advantage to students with recent educations. There is also demand for engineering technicians, a career path that generally requires an associate's degree and involves more training on the job.

Social Context and Future Prospects

Public transit systems have been a critical part of major cities for the last few centuries. With the development and mass production of the automobile, particularly since the 1950s, there were predictions that mass transit would be sharply reduced or would disappear completely. Cars, it was believed, would become the preferred way for people to get around for the foreseeable future.

Public opinion began to change in the late 1980s. Consumers were becoming more aware of the negative environmental impact of burning vast quantities of petroleum-based fuel. One response to this situation was the development of car engines that use energy more effectively, such as hybrid engines. Many consumers, particularly those living in large urban areas, also changed their habits and began to use public transportation or to ride bicycles more frequently. In the 2000s, large and sudden increases in gasoline prices gave consumers another incentive to choose a bus, train, subway, or bike ride over a car trip.

High fuel prices, traffic, and environmental concerns are forces that are likely to keep demand for public transit, and transportation engineering, steady in the twenty-first century. Transportation engineers will be asked to find new solutions for moving large numbers of passengers in cities where growth is taking place both downtown and in the far suburbs.

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