The project outputs were developed through an intensive process of capacity building and knowledge exchange across Europe, involving stakeholders from different sectors and strengthening the circular economy perspective in public transport. CE4CE also ensured strong collaboration with other projects, including joint events with Interreg projects e-MED, Degree4Alps and Circotronic, as well as with the Horizon Europe project eBRT. The development of key outputs was further supported by ICLEI European Secretariat and UITP, whose active involvement and wider community contributed significantly to shaping and disseminating the project results.
Our strategies and actions plans
The CE4CE strategies are built on the Circularity Compass and it’s AETE (Avoid–Extend–Transform–Enable) framework, applying a life-cycle perspective to public transport systems. Focusing on Energy, Infrastructure, and Rolling Stock, each strategy identifies both direct and embedded environmental impacts, explores opportunities to reduce resource consumption and emissions, and provides targeted recommendations to accelerate the transition towards more circular, resource-efficient, and net-zero public transport.
- Strategy for better use of waste energy and renewable energy sources in pubic transport operations
- Strategy to preserve value and reduce waste of public transport infrastructure
- Strategy to preserve value and reduce waste of public transport vehicles
The CE4CE Action Plans translate circular economy strategies into concrete local roadmaps for public transport operators across Central Europe. Developed by partners in Maribor, Leipzig, Gdynia, and Bergamo, they address key challenges related to energy efficiency, infrastructure management, electrification, renewable energy integration, predictive maintenance, and circular asset management, paving the way for more resilient, resource-efficient, and low-emission public transport systems. The four Action Plans prepared within the CE4CE project are:
- Action Plan to capture and use waste energy from trains and charge used batteries with renewable energy sources along new life cycle value chains based on municipal circular economy strategy and urban regeneration plan in Maribor, Slovenia
- Action Plan to optimise delivery of infrastructure through minimal invasive maintenance work at the Leipzig Transport Company (Leipzig, Germany)
- Action Plan to optimise delivery of infrastructure by cooperation and sharing between public providers, as update of municipal strategy for electromobility in Gdynia, Poland
- Action Plan to add value on the forward supply chain and optimise delivery of vehicles by circular procurement at ATB Mobility, Bergamo, Italy
The Guidelines for developing circular strategies in the public transport sector introduces the CE4CE approach to circularity, outlines the strategies developed under the four main project thematic areas – energy, infrastructure, rolling stock and governance – and showcases how these were translated into concrete local Action Plans. Drawing on practical experiences from strategy and action plan development, the document highlights key success factors, stakeholder engagement approaches, and recommendations to support the wider adoption of circular economy principles in the public transport sector. The guidelines are available in English and in all Central European languages on the project website in the Outputs section.
Our solutions
A key outcome of the CE4CE project is the Public Transport Circularity Compass, a practical tool that helps public transport operators and authorities assess the circularity of their systems and identify areas for improvement. Based on a whole life-cycle approach, the Compass supports the evaluation of vehicles, infrastructure, energy and governance, enabling organisations to uncover opportunities for more efficient resource use, reduced waste and lower emissions, while accelerating the transition towards more circular public transport systems. The short video about the Circularity Compass is available here.
The CE4CE Knowledge Platform serves as a digital hub for public transport stakeholders seeking to advance circular economy practices. Bringing together practical tools, best practice examples, knowledge resources and a dedicated matchmaking forum, the platform helps users identify circularity opportunities, better understand value chains, and connect with relevant partners. By facilitating knowledge exchange and collaboration, it supports the wider adoption of circular solutions across the public transport sector.
The following solutions developed within CE4CE are based on the practical experience and lessons learned from the pilot actions. This ensures that the results are not only theoretically relevant, but also reflect tested and applicable approaches in the field of circular public transport.
The output Modules for predictive maintenance of infrastructure and rolling stock involved the development of prototype modules for both infrastructure and rolling stock applications, building on pilot activities that equipped vehicles with sensors to collect infrastructure condition data (Digital infrastructure and vehicle optimization through predictive maintenance). These solutions were tested on selected sections of infrastructure and rolling stock to demonstrate their functionality and prepare for future scaling across the wider network. Transferability to other organisations is ensured through standardised interfaces, data formats and parameters, as well as a structured methodology for developing damage catalogues and conducting impact analyses.
The Circular business planning tool for electrified public transport fleets and infrastructure output developed a tool to assess the value and costs of measures aimed at extending the lifetime of infrastructure and vehicles while optimising energy use. It builds on the Gdynia pilot, which used digital twin modelling and energy flow simulations to evaluate different electrification scenarios. The tool enables the design of energy management scenarios based on investment costs and lifecycle assumptions for fleets and infrastructure. It also includes a cost-benefit analysis model integrating both internal benefits, such as extended asset lifetime, and external benefits, including environmental impacts. The tool is publicly available at https://ce4ce.ug.edu.pl/.
The output Definition of uptake criteria to re-use trolleybus switches builds on the Szeged pilot, where four high-speed trolleybus switches removed from the main network were successfully relocated to the depot, demonstrating a practical circular infrastructure solution. Based on SZKT’s experience, the document outlines key technical, operational, safety, maintenance, and certification requirements for reuse in different network environments. It provides practical guidance for extending component lifetimes, reducing material use, and supporting more cost-efficient infrastructure management. The results are intended to support knowledge transfer and future uptake by other public transport operators.
The output Develop transferable business models for re-use of batteries to store renewable energy sources in public transport systems builds on the Maribor pilot, which demonstrated the use of second-life batteries in a Battery Energy Storage System (BESS) to store renewable energy for fast-charging infrastructure. The solution was developed in cooperation with key value chain actors and provides guidance on technical, organisational, economic, and governance aspects of battery reuse. It also addresses existing legal barriers identified during the pilot and includes recommendations for necessary changes to relevant standards, supporting wider uptake and replication in other public transport systems.
The output Online second-hand and match-making market for used parts, products and information-sharing to crowdsource circular product-design based on information-sharing developed an online matchmaking platform to support information exchange and the reuse of components in public transport. It builds on the Szeged tram control unit remanufacturing pilot, which demonstrated reverse-engineering and redesign of obsolete door control electronics for Tatra trams. The solution enables life-cycle actors to share knowledge and technical information needed for adapting and maintaining tram components, as well as other critical parts. The platform supports circular product design and service development by facilitating collaboration between operators and suppliers. The matchmaking forum is available at https://circularity4publictransport.eu/matchmaking-forum/.
The CE4CE Handbook on pilots and solutions presents the project’s key pilot actions and solutions, developed through co-creation, real-life testing and peer review across Central Europe. It demonstrates practical circular economy applications such as lifetime extension, reuse, repurposing and remanufacturing of public transport assets, supported by digital tools and enabling business models. The handbook translates the project results into all CE languages, ensuring wide accessibility and supporting knowledge transfer and replication across different public transport contexts in Europe. The handbook translations are published on the project website in the Outputs section.
Capacity building and knowledge sharing
The CE4CE e-course is an online training programme designed to support public transport stakeholders in applying circular economy principles in practice. It is structured into five main units which cover the main project thematic areas, lessons learned from the pilot actions, jointly created solutions as well as useful strategies and measures with high replication potential. The course brings together contributions from both project partners, external experts (among which Cenex Netherlands, PKT Gdynia Poland, City of Biel Switzerland, Mobility Agency Budapest), as well as from the Advisory Board members ICLEI European Secretariat, UITP and EIT Urban Mobility), ensuring a mix of practical experience and specialist insights across all topics. Available via the Mobility Academy, it is self-paced and open for online registration, offering accessible learning to support more sustainable and resource-efficient public transport systems.
The CE4CE Hackathon on Circular Economy in Public Transport brought together students from universities in Maribor and Gdańsk to develop innovative solutions for real-world urban mobility challenges. Working in 15 teams, participants addressed pilot cases from Gdynia, Maribor, and Szeged, focusing on topics such as second-life batteries, resource efficiency, and circular reuse of transport components. The programme combined brainstorming sessions, guided work, and expert feedback, with all teams successfully completing their tasks and presenting solutions with strong potential for pilot improvement and future real-world application.
Two CE4CE policy workshops highlighted key barriers and solutions for scaling circular public transport. The first CE4CE policy workshop organised in the framework of the Cities Mission Conference in Vilnius, on 6-8 May 2025, identified major challenges such as fragmented procurement and funding, regulatory constraints, limited data standardisation, and cultural resistance to reuse, while stressing the need for EU-level policy alignment and better conditions for secondary markets and data sharing. In February 2026, public transport operators from Austria, Germany and Switzerland met in Salzburg for a CE4CE Policy Workshop on Circular Economy and Bus Procurement organised in Salzburg by the trolley:motion association. The event focused on how circular economy principles can be better integrated into public transport planning, procurement and operations, with discussions covering circularity criteria in tenders, lifecycle-based evaluation models, predictive maintenance, digital condition monitoring and energy optimisation. The workshop also provided space for strategic exchange between trolleybus and IMC operators, strengthening cross-border cooperation and knowledge transfer.
Project partners actively promoted the project results at major European events, including Transport Research Arena (2026), Mobility Move (2024, 2026), POLIS Annual Conference (2024, 2025), Urban Mobility Days (2025), InnoTrans (2024), CIVITAS Forum (2024), the European Week of Regions and Cities side events (2024, 2025), and thematic forums such as ACRPS Leipzig (2025), Navigate Mobility conference (2024, 2025), VDV-KI-Forum (2024), DCRPS Leipzig (2024), Tramway forum Norrköping, Sweden (2024), and others.
ICLEI European Secretariat and UITP actively supported CE4CE dissemination and stakeholder engagement as Advisory Board members. ICLEI organised for the signatories of the Circular Cities Declaration the webinar “Circular Economy in Public Transport and Urban Mobility” as a joint event with CE4CE, where several CE4CE partners contributed as speakers, facilitating knowledge exchange with the wider sustainability community. ICLEI also supported the promotion of project results through articles, participation in events, and dissemination via its own communication channels. UITP contributed by validating project outputs such as the matchmaking forum and the circularity compass, participating in project events and ensuring visibility at key sectoral platforms, including the UITP Summit (2025) and the UITP Trolleybus Committee biannual meetings.
With the CE4CE project now coming to an end, we would like to thank all partners, stakeholders, and contributors for their collaboration and commitment over the past three years. The project results will continue to support the development of circular solutions in public transport beyond its lifetime. All CE4CE videos are available on our YouTube channel, and the full set of project outputs can be accessed on the project website.