Source: Deutsche Nachrichten
Around one quarter of Europe’s CO₂ emissions and more than 15% of global CO₂ emissions originate from the transport sector. Approximately half of these emissions are generated by private road transport. Strengthening public transport is therefore recognised as a key pillar of the transition towards climate-neutral mobility.
One for All: The Bus as the Backbone of Public Transport
Local authorities are primarily responsible for planning and organising public transport. For economic reasons, they build on established networks while taking local conditions into account. Measured in passenger-kilometres, the bus remains the dominant mode of public transport. It carries the largest number of passengers, provides the highest number of vehicle-kilometres and accounts for the largest share of overall operating costs. At the same time, buses provide services in areas where rail-based systems, such as trams, cannot be justified by passenger demand.
The flexibility of the bus and its comparatively low infrastructure costs compared with suburban rail, tram and metro systems come at the expense of a weaker environmental performance. A conventional diesel bus has by far the largest carbon footprint in public transport, producing up to ten times the CO₂ emissions of a tram. It is therefore no surprise that the electrification of bus fleets has accelerated significantly in recent years. While electric buses currently account for an average of around 16% of bus fleets across the DACH region, this figure is expected to reach approximately 50% by 2030. By 2040, more than 90% of bus fleets are expected to be electrified.
Achieving this goal, however, is about far more than simply purchasing electric buses. Although electric buses often offer lower operating costs than diesel vehicles, their purchase price remains significantly higher. More importantly, their deployment requires substantial investment in charging infrastructure, electricity supply and depot facilities, together with new approaches to ensuring efficient, resource-conscious and economically sustainable operations.
The Depot – A Bottleneck for the Public Transport Transition
The daily distances covered by scheduled bus services can already be accommodated by the range of modern battery-electric buses in many networks. The real challenge of electrification, however, lies in the charging infrastructure.
While refuelling large diesel bus fleets has been routine for decades, the deployment of high-capacity charging infrastructure presents public transport operators with entirely new challenges. Berlin’s public transport operator (BVG), for example, is investing around €195 million in the charging infrastructure for its new depot, which will accommodate up to 440 electric buses. In the longer term, the necessary infrastructure must also be provided to support a fleet of more than 1,500 electric buses.
Operational complexity also increases significantly. Charging schedules must be coordinated with vehicle duties, buses allocated to available charging points, and sufficient grid capacity ensured. Even minor service delays can create conflicts in vehicle scheduling and operations.
Electrifying bus fleets therefore involves far more than simply replacing the drivetrain. It requires substantial investment in infrastructure, energy management and depot operations – posing major technical, organisational and financial challenges, particularly for small and medium-sized public transport operators.
The Trolleybus – Sustainability by Design
The trolleybus is one of the most sustainable, yet often underestimated, elements of the public transport transition. It combines the benefits of electric mobility with highly efficient and long-lasting infrastructure. Unlike battery-electric buses, trolleybuses do not require extensive, costly charging infrastructure or large batteries that depend on critical raw materials such as lithium, cobalt or nickel. Instead, they draw their power directly from the overhead line, achieving an energy efficiency of more than 90%, as electricity does not have to be repeatedly stored in and discharged from batteries. When powered by renewable electricity, their environmental performance improves even further. At the same time, complex charging processes at depots and terminal stops, together with the associated infrastructure costs and operational challenges, are largely eliminated.
From a circular economy perspective, trolleybuses offer significant additional advantages. Overhead line infrastructure has a service life of 30 to 50 years, consists primarily of steel and copper, and is almost entirely recyclable. In modern In Motion Charging (IMC) systems, the overhead line also serves as the charging infrastructure. As all power electronics are located on board the vehicle, the infrastructure remains independent of proprietary charging protocols and manufacturer-specific systems. Different vehicle manufacturers can therefore use the same overhead infrastructure, avoiding long-term vendor lock-in.
The vehicles themselves are also designed for longevity. Their modular construction and standardised components simplify maintenance, refurbishment and end-of-life recycling. Compared with battery-electric buses, IMC vehicles require significantly smaller batteries—typically only around one quarter of the battery weight—which, due to lower operating stress, generally achieve a longer service life.
Today’s IMC trolleybuses require overhead wiring on only 30 to 50% of a route. The remaining sections are operated using battery power. This allows the overhead infrastructure to be concentrated on heavily used corridors, where it is often shared by several routes. Modern overhead systems no longer require complex turning loops or dense overhead wiring and can be integrated discreetly, even into sensitive or historic urban environments. This further reduces both capital investment and maintenance costs. [FMit3.1]
The success of this approach is demonstrated by numerous cities around the world. In Zurich, San Francisco and Beijing, as well as on newly developed IMC routes, modern trolleybuses prove their reliability and cost-effectiveness every day, even under demanding topographical conditions and high passenger volumes. At the same time, IMC and battery-electric buses are not competing technologies. When overhead wiring and charging infrastructure are planned as an integrated system, both technologies can operate efficiently within the same network. Several Swiss cities already follow this technology-neutral approach, selecting the electrification solution that delivers the greatest technical, economic and environmental benefit for each individual route
trolley:motion – Expertise for the Future of Trolleybus Systems
Delivering sustainable bus systems requires specialised expertise. As Europe’s leading independent competence platform for trolleybus systems, trolley:motion brings together expertise from research, industry and operational practice. The organisation supports cities and public transport operators in the planning, financing and implementation of modern IMC systems, demonstrating how trolleybuses and battery-electric buses can be combined into efficient, high-performance and economically sustainable public transport networks.
How electrification, circular economy and economic efficiency can be brought together even more effectively will also be a key focus of the IMC – Trolleybus Conference 2026, taking place in Lyon on 12–13 November 2026. The conference will bring together international representatives from cities, public transport operators, industry, planning, consultancy, research and policy to exchange practical experience and discuss strategies for the next generation of sustainable bus systems.