Trolleybuses: Characteristics and Applications
(extract from Urban Transit: Systems and Technology, John Wiley & Sons, Inc. 2007)
by Vukan R. Vuchic (reproduced with authors permission)
The overall characteristics of the trolleybus mode are rather similar to those of diesel buses, but physical differences between the two technologies do bring some significant distinctions. In summary, trolleybuses have the following characteristics.
Steering control and vehicle bodies are practically identical for trolleybuses and buses. However, electric propulsion gives trolleybuses performance characteristics similar to those of rail modes: powerful traction and fixed alignments. The combination of rubber tires with electric propulsion provides trolleybuses with two excellent qualities: good performance and low negative environmental impact. Their high but smooth acceleration and grade-climbing ability are very much appreciated by passengers. Their extreme quietness (trolleybuses produce less noise than any other transit mode) and absence of air pollution are popular with both the riders and the population in the areas served. The only negative impact may be aesthetically poor overhead wire networks at junction points, where they are often elaborate.
Disadvantages of trolleybuses include the costs of installation and maintenance of overhead wires and incidental dewiring of trolley poles. The ability to temporarily change alignment depends on vehicle design: trolleybuses with auxiliary ICE motor can travel several blocks without wire contacts. The most serious drawback is the approximately 50% higher price of trolleybus than bus vehicles. The approximately 50% longer life of trolleybuses (15 to 20 years versus 10 to 12 years for buses) compensates somewhat for this difference, however.
Operating costs of trolleybuses depend largely on the price of electricity. Energy costs for the operation of trolleybuses are in some areas higher, in others lower than those for the operation of diesel or other ICE buses. Many cities willingly pay the higher costs of trolleybuses because they consider it worthwhile for the superior features of trolleybuses, such as better performance, environmental friendliness, and use of electricity, which can be generated from any primary energy source.
This review of their characteristics shows that most of the advantages of trolleybuses concern passengers and the population in the areas served, while most of their disadvantages affect operators. When a transit agency is in financial straits, it is inclined to reduce its costs by converting trolleybus lines to buses, thus sacrificing the largely intangible, although not insignificant, benefits to the public.
This dichotomy of public and operator's interests with respect to trolleybuses has had a major impact on applications of this mode. During the 1930s and 1940s, when transit ridership was high and investment funds were available, trolleybuses were introduced in many cities. With increasing volumes of autos on urban streets and continuous attempts to accommodate them and with decreasing ridership and the disappearance of investment funds, massive conversion of trolleybuses to diesel bus services took place. In Great Britain, which had trolleybus systems in many cities (including 1500 vehicles in London alone) at the time of World War II, this mode has been completely eliminated. Most trolleybus services have also been discontinued in Denmark, the United States, and other countries.
During the 1960s, it did not appear that trolleybuses could retain any significant role in urban transportation. However, several developments since 1970 led to a change in attitude toward this mode. The influencing developments have been:
The introduction of public financial assistance to transit, which led to increased attention to quality of service rather than only minimum cost.
Emphasis on improving the environment, which led to recognition of the excellent features of trolleybuses with respect to noise and air pollution.
Reduced dependence on oil through use of electric propulsion became an important factor: recent trolleybus models with thyristor chopper control may allow absolute reduction in energy consumption over buses.
As a result of these developments, conversion of trolleybuses to buses was stopped and new vehicles have been purchased in recent decades by several U.S. and Canadian cities which operate this mode.
About year 2005, trolleybuses are operated in over 300 cities in the world, among them five U.S. and two Canadian cities. Eastern European countries use this mode extensively, as do some Asian and Latin American countries. Renovation and some network expansion is taking place in some European and North American cities (Athens, Bern, Luzern, San Francisco, Seattle, Vancouver). Advanced vehicle models have been produced in recent years in several countries, including Switzerland, Austria, Czechoslovakia, France, Russia, and Belarus.
Primary conditions that make trolleybuses advantageous in a comparison with buses are one or a combination of the following:
Hilly terrain (Belgrade, San Francisco, Seattle).
Importance of low noise and no air pollution (e.g., historic cities such as Athens and Salzburg).
Moderate to heavy passenger volumes (Athens, Milan, Sao Paulo).
Use of electricity preferred to oil (performance, reduction of oil imports, etc. Switzerland, east European countries, Russia, China).
Municipal ownership of electric power supply systems.
Although no major resurgence in the use of trolleybuses appears imminent, the downward trend in trolleybus use has generally stopped. It is likely that this mode will retain a significant role and enjoy popularity in a number of cities.
Vukan R. Vuchic PhD - UPS Foundation Professor of Transportation Engineering, University of Pennsylvania, copyright 2007
Published by John Wiley & Sons, Inc. 2007.
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Transport Revolutions website
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