Because of the continuous catenary, trolley buses are not flexible enough in the event of disturbances on their route. Furthermore, the overhead line is comparatively expensive because of its double tracked construction as well as cost- and service intensive elements such as crossings, switches, section insulators and tight bends.
Nevertheless, from an economic point of view, trolley buses present an attractive alternative to other concepts of electric buses. Equipped with a small battery system, the buses are able to tide over short route sections without overhead lines. This principle is called partial catenary. Therefore the capacity of the batteries has to be designed to tide over short distances (e.g. 5 - 20 km). This would make trolley buses more flexible than other electric buses, because they have to stop while charging. Trolley buses, in contrast could be charged from the catenary – while driving. This is particularly important for a smoothly operating timetable schedule. Complex, cost- and service intensive elements as outlined above could be omitted. This will not only save substantial costs in terms of the catenary, but also protected areas and interchanges could be traversed without overhead lines.
Last but not least, the new trolley buses would only be affected by disturbances on their route in the same way as other road users experience them too.
All of the above make trolley buses interesting again for town planners and transportation companies, particularly in consideration of environmental factors. But one problem remains: the current collectors and the trolley line often have to be dis- and reconnected several times en route.
The process of connecting is still done like a century ago – manually. In rare cases the connecting can be realized with so-called “wiring funnels”. But both methods conflict a frequently connecting.
The outcome of this is the projects objective: The connecting process has to be automated, since it is the main requirement for a partial catenary.