Banner image of an electric trolleybus

Electric Trolleybuses

Electric trolleybuses, often abbreviated as ETBs, have a lengthy service history in all corners of the world and are known to cope with the most severe of climates and service conditions. They are considered proven technology.

Trolleybuses draw power from overhead wires located above the roadway for all or part of their route, in much the same manner as a streetcar, tram or LRT vehicle. They typically operate on 600 or 750 volts. Because they can draw power directly from the grid, they can be highly energy efficient as the energy conversion and storage losses are less than those of other electric technologies. They emit no fumes into the streets, and they operate quietly.

Modern trolleybuses can be and usually are equipped with batteries that charge when they operate under wire, and these batteries can allow for regular off-wire operation for considerable distances. This is known as “In Motion Charging” (IMC). This means that in a modern trolleybus system, as little as 1/3 of a given route may actually be under wire—depending on factors such as vehicle specifications, climate and route length. Wire can be installed in central areas where it can be shared by several routes, and the vehicles may diverge from this wire to serve unwired areas.

Unlike battery buses, trolleybuses do not require infrastructure inside the garage or depot to charge them when they are not in service. In fact, in modern trolleybus systems, there is typically no wire in the garages or storage depots other than what is required to make a connection to the line voltage for servicing in the maintenance shop. The vehicles move in, out and about the garage or depot on battery power.

Trolleybuses are the most reliable of all electric buses. This is mostly because they have been in use for many decades, and their technology has evolved as the vehicles evolved. If power is drawn from green sources, they are also the most environmentally responsible electric bus because, although they are typically equipped with batteries, they do not require as many batteries as a battery electric bus would, and therefore do not pose the same level of environmental hazard associated with battery production and disposal. Trolleybuses also have the best performance of all electric buses, particularly when under wire, and they are easily heated or air-conditioned without the need to consume onboard power. They are considered to be a high performance vehicle.

Trolleybuses typically cost more to install than other types of electric buses because the infrastructure required for their operation is more extensive. Therefore, one would normally select busy, high patronage routes for trolleybus operation so as to offset the higher investment with higher revenue and to capitalize on the trolleybus‘ superior performance characteristics.

Trolleybus infrastructure has a very long lifespan, so they are considered a long term investment, with the investment being depreciated over a period of 60 years or more. What is important to realize is that the conversion from internal combustion to electric vehicles will not come without very large investments regardless of the type of electric vehicle chosen, and so if trolleybuses are being installed on suitable routes, that would represent a sound investment in electric public transport for decades to come.

Trolleybuses are currently used in around 300 cities throughout the world. A number of European cities that had abandoned trolleybus operations in the past have built new trolleybus systems. It is anticipated that trolleybuses will form a key component in the transition to an all-electric public transportation system in San Francisco, Seattle and Vancouver in the 21st century.


Further Information

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(Credit: City for All)