It did not take very long after a practical electric motor was developed to think of its placement in a vehicle. This would have required a rather long extension cord to supply power, but that problem could be solved by running a pair of live wires parallel to the path with rolling or sliding contacts linking them to the vehicle. Obviously, bare high-voltage wires could not be placed where people might touch them, but overhead was safe enough. That’s all there is to the trolleybus concept (except that the moving power pick-up arrangements appear to have generated the need for more engineering attention than anything else in the early days.)

Experiments with such transport devices started in the late 1880s, with working models being built in both Germany and France. They were not reliable or sturdy, but they proved that it could be done. The first regular services were opened in Germany – in Konigstein-Bad Konigsbrunn, as developed by Werner von Siemens (1901), and in Bielatal by Max Schiemann (1902). This was followed by a number of other lines not only in Germany, but also in Italy, Switzerland, Great Britain and Denmark. In the United States prior to World War I, besides some demonstrations, a short trolleybus route was in operation in Hollywood (Laurel Canyon, 1910), and for a very brief period in Merrill, Wisconsin (1913). All these efforts remained very much in the shadow of streetcars, which at this exact time were expanding explosively in most cities, offering reasonably reliable and responsive service. Trolleybuses were attempted only in those instances where the demand was so low that the construction of costly tracks could not be justified. Since the streets at that time usually were in a sorry state and the vehicles not particularly resilient, the service was decidedly not attractive.

Starting in the 1920s, a series of efforts, while still separate and incremental, were initiated again to explore the possibilities and implement trolleybus routes in several cities of North America and Europe. Each was, in effect, a pilot project, and experience was gained and lessons learned. Toronto, for example, instituted operations utilising vehicles built by Packard; Staten Island in New York City had a fleet of trolleybuses manufactured by the Atlas Truck Company. In Great Britain, Birmingham experimented with double-deckers, and petrol-electric vehicles – true harbingers of a distant future – ran between Middlesbrough and Easton. The latter had an auxiliary internal combustion engine, allowing the vehicle to leave the power line. Several other cities in North America attempted trolleybus service, but they all failed with the exception of Philadelphia, which started this mode then and still has it today. The Staten Island effort is deemed to be the first truly successful trolleybus operation in the United States.

Toward the end of the 1920s, technology was sufficiently advanced to develop new models from the ground up that could offer fast and smooth running, good and quiet acceleration, and the use of low cost power. Much of this was achieved by designing the trolleybus as a light over-the-road vehicle with pneumatic tyres, rather than as a sturdy streetcar. Better brakes and a workable power pickup (from under the wires) resulted in a suitable vehicle. Particularly successful was the design by Guy Motors of Great Britain, first introduced in Wolverhampton and then used widely in London.

This was also the period when streetcars came to be seen as obsolete transportation devices, candidates for wholesale replacement. This happened in London, but also several cities in France, and on a massive scale in American communities. In most cases the replacements were motor buses, but trolleybuses were seen as a “modern” approach as well, particularly in places that wished to preserve the investment made in electrical power distribution networks but could no longer afford to lay and maintain track and wished to be relieved of the obligation to maintain street pavements that streetcar companies carried. (Many streetcar franchises placed considerable burdens of street maintenance on rail operators.)

The first large-scale effort in the United States was the implementation of an extensive trolleybus system in Salt Lake City (1928) employing the new, more efficient vehicles. A contributing factor in this and several other instances was the opportunity to use public streets at no additional costs, because street surfaces by this time had been improved considerably in response to the demands of automobile owners. Other communities monitored the Salt Lake City experience and reached favourable conclusions. Chicago followed next (1930) with a sizeable network and several routes that accommodated large passenger loads previously not considered feasible. (50,000 daily patrons on a route, some with 45-second headways).

The 1930s were a significant expansion period for the trolleybuses in North America, boosted by transit demands during World War II. Notable among the many communities that embarked on this path is Seattle, which made a complete conversion starting in 1939 and built a system with 100 route-miles and 300 vehicles. That service is still basically in operation. The other large effort of that period was found in the old urbanised areas of northeastern New Jersey. The Public Service Coordinated Transport Company there established a complex network of routes and a diverse fleet of rolling stock that included trolleybuses with gasoline engines to reach sections of routes without power lines. They were manufactured by Yellow Coach Company and operated from 1935 to 1948. No trace remains of these operations, replaced by areawide bus service.

By 1940, some 60 communities in the United States had trolleybus service, accommodated by 2800 vehicles. In the early 1950s, which represent the peak period for this mode, there were more than 6500 units in operation. Thereafter, a period of decline commenced. After the war years, which were characterised by deferred maintenance, the infrastructure and the vehicles had worn out, but, with the onset of a precipitous drop in transit ridership, no capital-intensive efforts could be supported. Acquisition and operating costs of trolleybuses started to escalate, particularly in comparison to regular buses – presumably because of the smaller size of these operations and lack of any economies of scale.

There had been no particular incentives to upgrade the simple technology and the vehicle itself, which had not changed for decades. Above all, the service was seen as inflexible and the wires unsightly. There were several technical improvements in the late 1960s, but they came from general upgrading of electric and electronic elements by the basic industries in Europe and North America. Chopper control, for example, reduced power consumption considerably and assured smooth changes in speed. Regenerative braking and better power contacts were also introduced. None of this made much difference, and the decline continued.

There were no effective spokespeople for trolleybuses until concern with air pollution and city streets became a pervasive public issue. But by that time, however, it was too late to generate significant momentum back to a mode that had lost its general appeal. The petroleum fuel crises of the 1970s did not change matters either, beyond generating some discussion.

Despite all the early important development work in Great Britain, all trolleybus services were abandoned in that country. This almost happened in North America too. After all, these vehicles do constrain automobile flow on streets. The last trolleybus ran in New York City (Brooklyn, to be specific) in 1960. Even in Seattle the route miles dwindled down from 100 to 26. A watershed event was the closing of trolleybus services in 1973 in Chicago, which once had the largest system in the United States. Toronto stopped in 1961 and Calgary in 1975.

At this time (since 1973), only five American cities have trolleybuses: Boston, Dayton, Philadelphia, San Francisco and Seattle. There are two more in Canada (Edmonton and Vancouver), and two in Mexico (Mexico City and Guadalajara). At the peak of their operation in the early 1950s, trolleybuses represented about 10 percent of the transit activity in the United States; today they accommodate less than 1 percent of the national total.

The events were not quite as dramatic in the rest of the world. Some countries in Western Europe, particularly Switzerland and Germany have upgraded trolleybus technology and have strong operations in several places. A number of developing countries, particularly those that are reluctant to import expensive petroleum-based fuels but can produce sufficient electrical energy, have turned to this mode.

The largest systems with the greatest number of applications however are found within the former socialist bloc. As is not uncommon, the claim has been made that a Russian engineer produced the first trolleybus – an electric autotrain with six cars at the beginning of the twentieth century. The USSR had a single-minded policy of promoting this hardware within all the countries and cities under its rule because electric energy was considered to cost only half as much as petroleum-based fuels. All of the more than 26,000 vehicles (Several ZIU models) that were in operation at one time across the empire and its satellites were produced by the Uritski Works. The technology was not particularly advanced, but the vehicles were robust. Several hundred cities received trolleybuses, and, regardless of the recent political changes, they are still there by and large. Because of economic constraints, new replacement vehicles are scarce. Thus Eastern Europe and China are the places to observe full-scale trolleybus operations, if not always at the best service level.